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Dictionary of networking

Dictionary of networking



အသံုး၀င္မယ့္ သူမ်ားေလ့လာနိုင္ပါတယ္...

အသံုး၀င္မယ့္ သူမ်ားေလ့လာနိုင္ပါတယ္...



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    Dictionary of networking Dictionary of networking Document Transcript

    • 2461book Page i Thursday, May 4, 2000 11:59 AM Introduction Networks are currently one of the fastest growing and most important developments in the computer industry. Not only are more and more PCs becoming parts of networks, but networked PCs are being incorporated into larger enterprise-wide applications so that ev- eryone in a company can access and share data. With the expanding technology of networking comes the terminology to describe it. This Dictionary of Networking provides definitions for all the terms you will encounter when dealing with networks of any type. Who Should Use This Book? This book is designed to meet the needs of people who work with networks, communica- tions, and mobile computing systems. Whether you are networking previously uncon- nected computers or downsizing from a mainframe, this book is for you. And if you are studying for one of the network certification exams, you will find this book to be an es- sential reference. Network users of all levels are barraged with an almost bewildering array of terms, ab- breviations, and acronyms in books, magazine and newspaper articles, advertisements, and their day-to-day conversations. Jargon is a useful shorthand, but it can easily become incomprehensible and unmanageable, even to the most seasoned network administrator. What You’ll Find in This Book Along with clear explanations of the jargon and slang associated with networking, you’ll find definitions of more than 3,000 networking technical terms, abbreviations, and acro- nyms. The list that follows gives you a brief overview of the topics that this book covers: I Acronyms and abbreviations I Active Directory I ActiveX I Application software I Cables, cards, and connectors I Certification schemes I Chips, memory, and adapters I Communications Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page ii Thursday, May 4, 2000 11:59 AM Introduction I Connectivity tools, products, and equipment I Disks and storage media I E-mail I Hardware I File systems I Industry standards I Internet organizations I Internet terms and abbreviations I Intranet terms and abbreviations I Java I Leading hardware and software companies I Linux, Free Software Foundation, GNU I Microprocessors I Microsoft Windows I Microsoft Windows NT and NT Server I Microsoft Windows 2000 I Mobile computing I Networking theory and concepts I Novell NetWare I Novell Directory Services I Operating systems and environments I The OSI Reference Model I Popular networking products I Protocols and interfaces I Security and network administration I System architectures I Trade associations ii Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page iii Thursday, May 4, 2000 11:59 AM Introduction I Unix shells, tools, and utilities I The World Wide Web I Workstations How This Book Is Organized This book is organized for easy reference. Entries are arranged in letter-by-letter alphabetic order, ignoring punctuation and spaces, with terms that begin with an uppercase letter (or are all in uppercase) before those in all lowercase letters. So Internet comes before internet, and link level comes before link-state routing algorithm. Numbers and symbols are listed at the beginning of the book in ascending numeric order. If an entry begins with a letter or letters, but contains a number, it is listed alphabetically according to the letter, and then ac- cording to numerical order, so V.42 bis comes between V.42 and V.54. The information within each entry is always presented in the following order: I Entry name I Abbreviation or acronym I Pronunciation, if it isn’t obvious I Definition, written in clear standard English I URL pointing to further resources available on the Internet. I Cross-references to other entries that provide additional or related information on the topic; more on the cross references in a moment. If an entry has multiple definitions, each one is numbered to separate it from the next, and some of the entries also contain illustrations. Extensive Cross-Referencing The Dictionary of Networking is the most extensively cross-referenced dictionary of com- puting and networking terms available today. It contains two kinds of cross references: I A See reference points to another entry that contains the information you are looking for. Thus, you can start with an abbreviation, such as PPTP, or with the complete term, such as Point-to-Point Tunneling Protocol, and be sure that you will arrive at the cor- rect definition. You don’t have to know what an abbreviation stands for to be able to look up a term. Some terms or concepts can be referred to by more than one name, such as dialback modem and callback modem; you will find both here, so you can always find your way to the appropriate definition. iii Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page iv Thursday, May 4, 2000 11:59 AM Introduction I A See also reference points to one or more entries that contain additional information about a topic. This kind of cross-reference allows you to follow through a related set of entries, broadening your search as you move from entry to entry. We have also added an extra element in this dictionary to help you find information, and that is the pronunciation of an acronym or abbreviation that is pronounced differ- ently from the way it is spelled. For example, if you are reading a magazine article and come across the abbreviation SCSI, you can look up the abbreviation, which will point to the main entry term, Small Computer System Interface. But if you are discussing hard disk interfaces with a colleague and hear the term scuzzy, you can look that up too, and you will also find your way to the main entry, Small Computer System Interface. The Appendices This book contains four appendices to provide additional reference material: Appendix A: Internet Resources Collects together URLs under a wide variety of head- ings to cut down on the amount of time you have to spend with your favorite search en- gine. Using this appendix, you can go straight to the right Web site every time. Appendix B: Certification Resources Provides a guide through the complex and con- fusing world of computer and networking certification programs. Appendix C: ASCII Charts Contains both the standard and the extended American Standard Code for Information Interchange charts. Appendix D: EBCDIC Chart Contains the most widely accepted Extended Binary Coded Decimal Interchange Code chart. A Note about the URLs in This Book Nothing is more annoying than a dead URL, and link rot is all pervasive. (If you don’t know what link rot is, go look it up.) All the URLs in this book have been individually checked by our Technical Editor; and at the time of writing, they are all active, they all work, and they all contain the information that I say they contain. But that is not to say that some of them won’t have changed by the time you try them out. The better-organized sites will simply post a link to the new site if they make substantive changes, and you can use that new link to go right to the new or reorganized site. Other sites, such as the Microsoft Web site, reorganize themselves periodically as a part of their housekeeping; the information you want is still available, but you have to look in another place to find it, or use the site’s built-in search engine to find it. iv Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page v Thursday, May 4, 2000 11:59 AM Introduction Some of the sites that contain the most advanced technical information belong to the .edu domain and are usually computer science departments at the major universities. I have tried to keep the number of such sites to a minimum in this book. Although they can be ex- tremely useful, they usually have a lifespan that closely resembles that of the average grad- uate student. Once the student maintaining the information graduates, the site becomes neglected and is usually removed soon after. Another dead URL. To be consistent with current usage, I have not specified the protocol used to access each Web site; unless a different protocol is specified, you can simply assume that HTTP will work in all cases. Just add http:// to the beginning of each Web address in your browser when you access a site. And finally, we have tried very carefully not to break a URL across a line; you should be able to type the characters you see without having to worry about whether to type that hyphen. If a URL has to break, the break is before a period (.) or after a slash (/). About the Companion CD The companion CD contains an electronic version of this entire book. You can use it to find entries quickly and follow cross-references without a great deal of page flipping. And Finally… Through more than 25 years of hands-on involvement in practical computer applications, including the management of minicomputer systems, PC-based networks, large-scale data communications systems, software development, and technical support, I have become in- timately familiar with computer and networking terminology. The Dictionary of Network- ing is a direct result of that experience, and it represents a practical and down-to-earth approach to computers and computing. Everyone who has worked on this dictionary has tried to make sure that it is as complete and accurate as possible. But if you think that we have missed a word or two that should be included in a future edition, or if you think that an entry doesn’t contain enough infor- mation, please write to the following address: Dictionary of Networking c/o SYBEX Inc. 1151 Marina Village Parkway Alameda, CA 94501-1044 USA v Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 1 Thursday, May 4, 2000 11:59 AM 4.4BSD Lite Symbols and Numbers ! See bang. 3Com Corporation One of the largest manufacturers of network hardware in the & See ampersand. world, particularly known for LAN and * See asterisk. WAN products, including remote access products, hubs, network interface cards, *.* See star-dot-star. Gigabit Ethernet, and multimedia over net- works. The company’s PalmPilot hand- . See period and double-period held computer has proved to be extremely directories. popular, with more than one million units .. See period and double-period sold to date. In 1997, 3Com merged with directories. U.S. Robotics in a deal worth $6.6 billion. / See slash. For more information on 3Com, see www.3com.com. // See double-slash. 4B/5B encoding A data-translation : See colon. scheme used to precede signal encoding in FDDI (Fiber Distributed Data Interface) <> See angle brackets. networks. In 4B/5B, each group of four bits > See right angle bracket. is represented as a five-bit symbol, which is then associated with a bit pattern, which in ? See question mark. turn is encoded using a standard method, @ See at symbol. often NRZI (non-return to zero inverted). See also Manchester encoding. See backslash. | See vertical bar. 4.4BSD Lite A version of the 4.4 Berke- ley Software Distribution (BSD) Unix from 1/4-inch cartridge See quarter-inch which all the AT&T code has been re- cartridge. moved in an attempt to avoid licensing 2B+D Common abbreviation for Basic conflicts. It is not possible to compile and Rate ISDN, which has two B, or bearer, then run 4.4BSD Lite without a preexisting channels and one D, or data, channel. system because several important utilities and other files from the operating system See also 23B+D; Basic Rate ISDN. are missing. 3+ A network operating system, originally The 4.4BSD Lite version has served as the developed by 3Com, that implemented Xe- basis for several other important Unix rox Network System (XNS) transport pro- implementations, including FreeBSD and tocols and Microsoft MS-Net file sharing. NetBSD. 1 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 2 Thursday, May 4, 2000 11:59 AM 5B/6B encoding See also Berkeley Software Distribution coaxial cable; sometimes called thicknet. Unix; FreeBSD; NetBSD; Unix. The 10Base5 specification has a data-trans- fer rate of 10Mbps and a maximum cable- 5B/6B encoding A data-translation segment length of 500 meters (1650 feet), scheme used to precede signal encoding in over a bus topology. The cable attaches to 100BaseVG networks. In 5B/6B, each the Ethernet adapter with a vampire, or group of five bits is represented as a six-bit piercing, connector and a transceiver. symbol, which is then associated with a bit See also bus network. pattern, which in turn is encoded using a standard method, often NRZI (non-return 10BaseF An implementation of the to zero inverted). 802.3 Ethernet standard over fiber-optic See also Manchester encoding. cable. This specification allows throughput of a maximum of 10Mbps and is separated 9-track tape A tape storage format that into these three categories: uses nine parallel tracks on 1/2-inch, reel- to-reel magnetic tape. Eight tracks are used I 10BaseFP (fiber passive) Used for desk- for data, and one track is used for parity in- top connections formation. These tapes are often used as I 10BaseFL (fiber link) For intermediate backup systems on minicomputer and hubs and workgroups mainframe systems; digital audio tapes I 10BaseFB (fiber backbone) Used for (DATs) are more common on networks. central facility lines between buildings See also quarter-inch cartridge. 10BaseT An implementation of the 10/100 A term used to indicate that a de- 802.3 Ethernet standard over UTP wir- vice can support both Ethernet (at a data ing—the same wiring and RJ-45 connectors transfer rate of 10Mbps) and Fast Ethernet used with telephone systems. The standard (at a data transfer rate of 100Mbps). is based on a star topology, with each node See also Ethernet. connected to a central wiring center and a maximum cable-segment length of 100 10Base2 An implementation of the 802.3 meters (330 feet). Ethernet standard on thin Ethernet (RG-58) See also star network. coaxial cable; sometimes called thinnet or cheapernet wire. The 10Base2 specification 23B+D Common abbreviation for Prima- has a data-transfer rate of 10Mbps and a ry Rate ISDN, which has 23 B, or bearer, maximum cable-segment length of 185 channels and 1 D, or data, channel. meters (610.5 feet). A T-connector attaches See also 2B+D; Primary Rate ISDN. the thin coaxial cable to the BNC connector on the Ethernet adapter. 24/7 Abbreviation for round-the-clock 10Base5 An implementation of the availability, implying that the service is 802.3 Ethernet standard on thick Ethernet available 24 hours a day, 7 days a week. 2 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 3 Thursday, May 4, 2000 11:59 AM 802.x 56K modem standard See V.90. segmented-addressing scheme used by Intel coprocessors. 100Base-FX A specification for Fast Ethernet over fiber-optic cable. Several models have been developed: See also Fast Ethernet I 68000 The first microprocessor in this family, which used a 32-bit data word 100Base-T4 A specification for Fast with a 16-bit data bus and could address Ethernet over four pairs of Category 3, 4, or 16MB of memory. It was used in the first 5 untwisted-pair wiring. Apple Macintosh computers as well as in See also Fast Ethernet Hewlett-Packard’s LaserJet printers. I 68020 A 32-bit microprocessor that 100Base-TX A specification for Fast runs at 16MHz, 20MHz, 25MHz, or Ethernet over two pairs of Category 5 33MHz and is capable of addressing as unshielded twisted-pair or Category 1 much as 4GB of memory. The 68020 was shielded twisted-pair cable. The 100Base- used in the Macintosh II computer, but TX specification requires two pairs of has been replaced by the 68030. wires. I 68030 Has a paged memory manage- See also Fast Ethernet ment unit built-in and, therefore, does not need external hardware to handle this 100VG-AnyLAN A term applied to the function. The 68030 is used in the Mac- IEEE 802.12 standard, originally developed intosh II and SE computers. by Hewlett-Packard and supported by Nov- ell, Microsoft, AT&T, and many others. I 68040 Incorporates a built-in floating- point processor and memory manage- The 100VG-AnyLAN specification modi- ment unit, along with independent 4KB fies the existing Ethernet standard to allow data and instruction caches. It can per- speeds of 10 or 100Mbps and uses the form parallel execution by using multiple, demand priority access method rather independent instruction queues. The than Carrier Sense Multiple Access/Colli- 68040 is used in the Macintosh Quadra sion Detection (CSMA/CD). A speed of line of computers. 100Mbps transmission is supported over Category 3 four-pair unshielded twisted- See also PowerPC. pair cabling. 802.x A set of communications standards See also demand priority; Fast Ethernet. defining the physical and electrical connec- 680x0 A family of 32-bit microproces- tions in LANs, originally defined by the In- sors from Motorola, used in Macintosh stitute of Electrical and Electronics computers and many advanced worksta- Engineers (IEEE). tions. The 680x0 is popular with program- A number followed by an uppercase letter mers, because it uses a linear-addressing indicates a stand-alone standard; a num- mode to access memory, rather than the ber followed by a lowercase letter indicates 3 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 4 Thursday, May 4, 2000 11:59 AM 802.1 either a supplement to a standard or a part The 802.3 standard includes the following: of a multiple-number standard. I 10Base2 An implementation of the Many of the IEEE standards have also been Ethernet standard on thin Ethernet cable, adopted by the International Organization with a data-transfer rate of 10Mbps and a for Standardization (ISO), whose standards maximum cable-segment length of 185 are accepted all over the world; IEEE stan- meters (600 feet). dards 802.1 to 802.11 are now also known I 10Base5 An 802.3 Ethernet standard on as ISO 8802.1 to 8802.11. You will see thick Ethernet cable, with a 10Mbps data- both designations in networking books and transfer rate and a cable-segment length magazines; it will take a while for everyone of a maximum of 500 meters (1650 feet), to get used to these numbers. over a bus topology. See also IEEE standards. I 10BaseT Establishes a standard for Ethernet over UTP wiring, the same wir- 802.1 An IEEE standard that specifies ing and RJ-45 connectors used with tele- the media-access-control level for bridges phone systems. The standard is based on linking 802.3, 802.4, and 802.5 networks. a star topology. Each node is connected to It includes a spanning-tree algorithm for a wiring center, with a cable-length limi- Ethernet media-access-control layer bridg- tation of 100 meters (330 feet). es and the heterogeneous LAN manage- I 1Base5 A 1Mbps network standard ment specification for Ethernet and token- with twisted-pair cable based on AT&T’s ring hubs. StarLAN. See also IEEE standards. I 10Broad36 Defines a long-distance Ethernet with a 10Mbps data-transfer 802.2 An IEEE standard that specifies the rate and a maximum cable-segment logical link sublayer of the data-link layer in length of 3600 meters (11,880 feet). the OSI protocol stack. The data-link layer I 10BaseF Explicitly specifies fiber-optic in the OSI protocol stack is divided into the cable in three settings; 10Base-FP (fiber logical link layer and the media-access-con- passive) for desktops, 10Base-FL (fiber trol layer. The logical link layer provides link) for intermediate hubs and work- framing, addressing, and error-control groups, and 10Base-FB (fiber backbone) functions. for central facility lines between buildings. See also IEEE standards. I 100BaseVG A 100Mbps Ethernet net- work developed by Hewlett-Packard and 802.3 An IEEE standard for CSMA/CD AT&T Microelectrics. (Carrier Sense Multiple Access/Collision De- tection) LANs, including both baseband and I 100BaseT A 100Mbps Ethernet devel- broadband networks. The baseband version oped by Grand Junction Networks. is based on the Ethernet network, originally See also 100VG-AnyLAN; Ethernet; Fast developed by Xerox Corporation. Ethernet; Gigabit Ethernet; IEEE standards. 4 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 5 Thursday, May 4, 2000 11:59 AM 1394 802.4 An IEEE standard for bus topolo- The specification has been called IVD (In- gy networks that use token passing to con- tegrated Voice and Data), but is now more trol access and network traffic, running at commonly referred to as Iso-Ethernet. 10Mbps a second. Token-bus networks See also IEEE standards; Iso-Ethernet. are sometimes used in manufacturing set- tings, but they are not often found in office 802.10 An IEEE Technical Advisory networks. Group (TAG) working on the definition of See also ARCnet; IEEE standards; Techni- a standard security model for use over a va- cal and Office Protocol. riety of network types that incorporates au- thentication and encryption methods. 802.5 An IEEE standard that defines ring See also IEEE standards. networks using token passing to control ac- cess and network traffic, running at 4 or 802.11 A proposed IEEE standard that 16Mbps. It is used by IBMs Token Ring will define wireless LANs, including network over STP, UTP, or fiber-optic spread-spectrum radio, narrowband radio, cabling. Also known as ANSI 802.1-1985. infrared transmission, and transmission See also IEEE standards. over power lines. See also IEEE standards. 802.6 An IEEE standard for metropoli- tan-area networks (MANs). It describes a 802.12 An IEEE working group defining DQDB (Distributed Queue Dual Bus) used the 100Mbps Ethernet 100VG-AnyLAN for transmitting voice, video, and data over originally developed by Hewlett-Packard two parallel fiber-optic cables, with signal- and several other vendors. ing rates in excess of 100Mbps per second. See also 100VG-AnyLAN; IEEE standards. See also IEEE standards; Switched Multi- megabit Data Services. 802.14 An IEEE working group defining standards for data transmission over tra- 802.7 An IEEE Technical Advisory Group ditional cable TV networks using cable (TAG) report on broadband networks car- modems. rying voice, data, and video traffic. See also IEEE standards. See also IEEE standards. 1394 An IEEE standard for a digital plug- 802.8 An IEEE Technical Advisory and-play bus, originally conceived by Apple Group (TAG) report on the use of fiber op- Computer in 1986. The 1394 standard sup- tics as alternatives to copper-based cable in ports a maximum of 63 nodes per bus and LANs. a maximum of 1023 buses. See also IEEE standards. Three speeds for device connections are 802.9 An IEEE advisory committee on in- available: tegrated data, voice, and video networking. I 100Mbps 5 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 6 Thursday, May 4, 2000 11:59 AM 3270 I 200Mbps cause of an error and can address 16MB of memory. I 400Mbps All devices are hot pluggable, and both self- 80386 Also called the 386DX and the powered and bus-powered devices can be 386. A full 32-bit microprocessor intro- attached to the same bus. Also known as duced by Intel in October 1985 and used in FireWire, 1394 uses six-pair shielded many IBM and IBM-compatible comput- twisted-pair cable and is intended for high- ers. The 80386 has a 32-bit data word, can end applications such as digitized video. transfer information 32 bits at a time over the data bus, and can use 32 bits in address- See also Universal Serial Bus. ing memory. It has the following modes: 3270 A general description for the family I Real mode effectively limits performance of products from IBM that includes termi- to that of an 8086 microprocessor and can nals, printers, and terminal cluster control- address 1MB of memory. lers. These products all communicate with a I Protected mode prevents an application mainframe computer using the SNA (Sys- from stopping the operating system be- tems Network Architecture) protocol. cause of an error, and it can address 4GB of memory. 80286 Also called the 286. A 16-bit mi- croprocessor from Intel, first released in I Virtual 8086 mode allows the operating February 1982, used by IBM in the IBM PC/ system to divide the 80386 into several AT computer in 1984. Since then, it has virtual 8086 microprocessors, all running been used in many other IBM-compatible with their own 1MB of space, and all run- computers. ning a separate program. The 80286 uses a 16-bit data word and a 80486 Also called the 486 or i486. A 32- 16-bit data bus, with 24 bits to address bit microprocessor introduced by Intel in memory. It has two modes: April 1989. The 80486 adds several notable features to the 80386, including an on- I Real mode effectively limits performance board cache, a built-in floating-point pro- to that of an 8086 microprocessor and can cessor, and a memory management unit address 1MB of memory. (MMU), as well as advanced provisions for I Protected mode prevents an application multiprocessing and a pipelined execution from stopping the operating system be- scheme. 6 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 7 Thursday, May 4, 2000 11:59 AM accelerator board A A+ Certification A certification program Motorola 68020 or higher microprocessor from the CompTIA (Computer Technology and at least 4MB of memory to use A/UX. Industry Association) designed to measure See also Unix. competence in basic computer repair and aimed at the computer technician. Certifi- AAL See ATM Adaptation Layer. cation requires passing two tests: a core AASE See Associate Accredited exam to test general knowledge of PCs, in- Systems Engineer. cluding configuration, installation and up- grading, diagnosis, repair, maintenance, ABCP See Associate Business customer interaction, and safety, and at Continuity Professional. least one specialty exam that tests operating system knowledge. abend Contraction of abnormal end. A message issued by an operating system when A+B signaling A type of in-band signal- it detects a serious problem, such as a hard- ing used in T1 transmission; 1 bit from each ware failure or major software damage. of the 24 subchannels in every sixth frame is ABI See Application Binary Interface. used to carry dialing and other control infor- mation. A+B signaling reduces the T1 band- ABR See Available Bit Rate. width from 1.544Mbps to 1.536 Mbps. ABUI See Association of Banyan Users See also T1. International. accelerator board An add-in, printed a-b box A switching box that allows two circuit board that replaces the main proces- or more computers to share a peripheral de- sor with a higher-performance processor. vice such as a printer. It can be switched Using an accelerator board can reduce up- manually or through software. grading costs substantially, because you A/UX A version of the Unix operating don’t need to replace the monitor, case, system that runs on the Macintosh. A/UX is keyboard, and so on. However, the main based on the System V release 2 of Unix and processor is not the only component that af- includes a number of Apple features, such fects the overall performance of your sys- as support for the Macintosh Toolbox. This tem. Other factors, such as disk-access time support allows applications running under and video speed, contribute to a system’s A/UX to use the familiar Macintosh user in- performance. terface. You need a Macintosh II with a See also graphics accelerator board. 7 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 8 Thursday, May 4, 2000 11:59 AM access access To use, write to, or read from a along with the rights granted to that user file, or to log in to a computer system or or group. network. I In Windows 2000, everything is an object, and every object has an associated ACL. AccessBuilder Remote access software from 3Com Corporation that lets you ac- See also Active Directory; authentication; cess network resources over a dial-up con- NDS tree; Novell Directory Services; rights; nection from a remote location. security. access control entry Abbreviated access method The set of rules that de- ACE. The basic unit of security in Mi- termines which node in a network has ac- crosoft Windows 2000 that controls access cess to the transmission media at any to the file system, to Active Directory ob- moment. jects, to printers and other network re- Attempts at simultaneous access are either sources, and to the Registry. managed by a collision detection mecha- An ACE consists of a security identifier nism such as CSMA/CD or prevented by (SID) and an access mask that defines the use of a token-passing method. access rights of that SID. A collection of access protocol The set of rules that ACEs that control access to an object is workstations use to avoid collisions when known as an access control list. sending information over shared network See also access control list; security media. Also known as the media access con- identifier. trol protocol. access rights See rights. access control list Abbreviated ACL. A list or table containing information about access server A computer that provides the users, processes, and objects that can ac- access for remote users who dial in to the cess a specific file or object. ACLs are usu- system and access network resources as ally attached to file-system directories, and though their computers were directly at- they specify access permissions such as tached to the network. read, write, execute, delete, and so on. See also communications/modem server; ACLs are implemented in Novell NetWare, mobile computing. Microsoft Windows 2000, and Unix: access time The period of time that I In Novell Directory Services, ACLs are as- elapses between a request for information sociated with every object in the NDS tree, from disk or memory and the arrival of that storing the list of rights for each trustee information at the requesting device. that can access the object. Memory-access time refers to the time it I In the Unix Network File System, ACLs takes to transfer a character between mem- include the name of the user or group, ory and the processor. Disk-access time 8 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 9 Thursday, May 4, 2000 11:59 AM ACF refers to the time it takes to place the read/ See also authentication; user account. write heads over the requested data. RAM may have an access time of 80 nanoseconds account policy On networks and mul- or less, while hard-disk access time could be tiuser operating systems, the set of rules 10 milliseconds or less. that defines whether a new user is permitted access to the system and whether an exist- access token In Microsoft Windows ing user is granted additional rights or ex- 2000, an object that contains the security panded access to other system resources. identifier (SID) of a running process. Account policy also specifies the minimum When a process is started by another pro- length of passwords, the frequency with cess, the second process inherits the starting which passwords must be changed, and process’s access token. This access token is whether users can recycle old passwords then checked against each object’s access and use them again. control list to confirm that the appropriate Accredited Systems Engineer Abbre- permissions are in place to permit any ser- viated ASE. A certification from Compaq vices requested by the process. designed to evaluate and recognize exper- See also access control list; permissions; tise in installing and administering Compaq process; rights. workstations and servers running both Mi- crosoft Windows 2000 and Novell Net- account On LANs or multiuser operating Ware network operating systems. systems, an account is set up for each user. See also Associate Accredited Systems Accounts are usually kept for administrative Engineer. or security reasons. For communications and online services, accounts identify a sub- ACE See access control entry. scriber for billing purposes. Acer Group One of the top five PC mak- See also user account. ers in the world, with factories in Malaysia, accounting The process of tracking the the Netherlands, the Philippines, Taiwan, resources on a network. The network ad- and the United States. The Acer Group ministrator can charge for files accessed, bought Texas Instrument’s notebook com- connect time, disk space used for file stor- puter business in 1997 and has formed busi- age, and service requests by assigning ac- ness alliances with companies, including count balances to users. The users can then 3Com and Hitachi, for the development of draw from their account balances as they advanced digital consumer products such use network services. as PC-ready televisions and DVD systems. For more information on the Acer Group, account lockout In Microsoft Windows see www.acer.com.tw. 2000 and other operating systems, a count of the number of invalid logon attempts al- ACF See Advanced Communications lowed before a user is locked out. Function. 9 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 10 Thursday, May 4, 2000 11:59 AM ACK ACK See acknowledgment. migration to upgrade from LAN Manager, LAN Server, and earlier versions of Net- acknowledgment Abbreviated ACK. In Ware; a similar process known as BMI- communications, ACK is a control code, GRATE allows users to migrate from ASCII 06, sent by the receiving computer to Banyan VINES. indicate that the data has been received without error and that the next part of the ACS See Advanced Communications transmission may be sent. Service. See also NAK. ACTE See Ascend Certified Technical Expert. ACL See access control list. Active Desktop In Microsoft Windows, ACONSOLE A Novell NetWare 3.x a user interface feature that makes the Desk- workstation utility that controls a modem top look and behave just like a Web page, attached to the workstation. ACONSOLE is with underlined icons and a hand mouse used to establish an asynchronous remote pointer. Active Desktop is offered as an al- console connection to a server. The RS232 ternative to the classic Windows user inter- NetWare Loadable Module (NLM) must be face; you can use Active Desktop, you can loaded on the server to which you want to use the classic Windows interface, or you connect. In NetWare 4.x, use RCONSOLE can swap back and forth between the two. to perform this function. Active Directory In Microsoft Windows acoustic coupler A modem that in- 2000, a system for large-scale network cludes a pair of rubber cups that fit over the management that views the network as a hi- mouthpiece and earpiece of a standard tele- erarchy of objects. Active Directory does phone handset (to prevent external noise the following: from being picked up). An acoustic coupler allows you to connect your computer to a I Provides a hierarchy for the management telephone system that does not have the of all network objects, including users, standard RJ-11 connections used with con- servers, services, file shares, Web pages, ventional modems. printers, and so on. I Divides administration and security into ACPI See Advanced Configuration and subdomains, domains, and trees of Power Interface. domains. ACR See Available Cell Rate. I Scales to 10 million users per domain. across-the-wire migration A method I Implements MIT’s Kerberos authentication of migrating file-server data, trustee rights, system based on private key encryption and and other information to a Novell Net- also supports public key encryption for Ware server using the NetWare Migration authentication of clients and business utility. You can also use across-the-wire partners. 10 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 11 Thursday, May 4, 2000 11:59 AM active termination I Emulates Windows NT 4.x directory ser- An active hub may have ports for coaxial, vices for backward compatibility. twisted-pair, or fiber-optic cable connec- I Uses DNS rather than WINS, and requires tions, as well as LEDs to show that each all user and host names to be in DNS port is operating correctly. form. See also repeater. I Uses LDAP rather than a proprietary pro- tocol so that non-Microsoft applications Active Monitor The first station to be can query the name database. started on a Token Ring network. The Ac- tive Monitor is responsible for passing and I Interoperates with Novell NetWare Di- maintaining the token and detects error con- rectory Services. ditions. The Active Monitor’s performance See also forest; Kerberos; Lightweight Di- is constantly monitored by the Standby rectory Access Protocol; NetWare Directo- Monitor ry Services; Microsoft Windows 2000; tree. See also Standby Monitor. Active Directory Service Interface Abbreviated ADSI. In Microsoft Active Di- Active Server Pages Abbreviated ASP. rectory, an application programming inter- In Microsoft Internet Information Server, a face (API) designed to simplify access to script interpreter and execution environ- Active Directory objects. ment that supports VBScript and Java- See also Active Directory; application pro- Script and is compatible with other script- gramming interface. ing languages such as Perl, REXX, Tcl, and Python through add-ins from third-party Active Directory Users and developers. Computers Abbreviated ADUC. In Mi- ASP allows you to combine HTML, scripts, crosoft Windows 2000 Server, the main ad- and ActiveX components on the same Web ministrative tool used to manage user server; all the code runs on the server and accounts, security groups, organizational presents the results of this dynamic process units, and policies. to the client browser as a standard HTML ADUC is a Microsoft Management Con- page. sole (MMC) snap-in and replaces Windows See also JavaScript; Perl; Tcl; VBScript. NT User Manager. See also Active Directory; Microsoft Man- active termination A technique used to agement Console; snap-in. terminate a SCSI. Active termination reduc- es electrical interference in a long string of active hub A device that amplifies trans- SCSI devices. mission signals in a network, allowing sig- nals to be sent over a much greater distance See also forced perfect termination; pas- than is possible with a passive hub. sive termination. 11 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 12 Thursday, May 4, 2000 11:59 AM active window active window The window currently See also ActiveX; certificate; Java; Java accepting mouse clicks and keyboard input. applet; Java Virtual Machine; sandbox. The title bar of the active window is always a different color from that of the other open AD See Active Directory. windows. Adaptec, Inc. A leading manufacturer of ActiveX The latest development of Mi- high-performance networking and connec- crosoft’s COM, the foundation that sup- tivity products, including SCSI adapters, ported OLE. By adding network capabilities RAID products, Fast Ethernet adapters, (and so creating DCOM, or Distributed ATM network interface cards, and server COM) and by reducing the scope of OLE to management software. In 1998, Adaptec create ActiveX, Microsoft has created a acquired Ridge Technologies, a manufac- comprehensive set of component-based turer of RAID and other storage solutions Internet- and intranet-oriented applications. for Microsoft Windows 2000. In an attempt to promote ActiveX as a stan- For more information on Adaptec, see dard, in 1996 Microsoft turned over con- www.adaptec.com. trol of ActiveX to the Open Group to adapter A printed circuit board that manage future developments. plugs into a computer’s expansion bus to See also ActiveX control; Distributed Com- provide added capabilities. ponent Object Model; Java. Common adapters include video adapters, ActiveX control The basic building joy-stick controllers, and I/O adapters, as block of Microsoft’s ActiveX specification. well as other devices, such as internal mo- An ActiveX control is a software module dems, CD-ROMs, and network interface that cannot run by itself, but requires an Ac- cards. One adapter can often support sev- tiveX container such as a Web browser, a eral different devices. Some of today’s PC word processor, or a spreadsheet. Each designs incorporate many of the functions control delivers a specific function such as previously performed by these individual database access, user-interface elements, or adapters on the motherboard. file access and can communicate with an- adaptive equalization See adaptive other ActiveX control, an ActiveX contain- speed leveling. er, or the underlying Windows operating system. adaptive routing A mechanism that al- Unlike Java applets, which for security rea- lows a network to reroute messages dynam- sons run in a sandbox designed to protect ically, using the best available path, if a the file system from unauthorized access, portion of the network fails. ActiveX can directly access files. To provide See also alternative route. a measure of security, ActiveX controls are packaged with digital certificates that prove adaptive speed leveling A modem the origin of the control. technology that allows a modem to respond 12 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 13 Thursday, May 4, 2000 11:59 AM address classes to changing line conditions by changing its transmit the signals that specify locations in data rate. As line quality improves, the mo- memory. dem attempts to increase the data rate; as The number of lines in the address bus de- line quality declines, the modem compen- termines the number of memory locations sates by lowering the data rate. Also known that the processor can access, because each as adaptive equalization. line carries one bit of the address. A 20-line ADCCP See Advanced Data Communi- address bus (used in early Intel 8086/8088 cations Control Procedures. processors) can access 1MB of memory, a 24-line address bus can access 16MB, and a address 1. The precise location in mem- 32-line address bus can access more than ory or on disk where a piece of information 4GB. A 64-line address bus (used in the is stored. Each byte in memory and each DEC Alpha APX) can access 16EB. sector on a disk has its own unique address. address classes In a 32-bit IP address, 2. The unique identifier for a specific node which is shown in the accompanying illus- on a network. An address may be a physical tration, the number of bits used to identify address specified by switches or jumpers on the network and the host vary according the network interface card hardware, or it to the network class of the address, as can be a logical address established by the follows: network operating system. I Class A is used only for very large net- 3. To reference or manage a storage works. The high-order bit in a Class A location. network is always zero, leaving 7 bits 4. In Unix, an IP address as specified in the available to define 127 networks. The re- /etc/hosts file. maining 24 bits of the address allow each 5. Information used by a network or the In- Class A network to hold as many as ternet to specify a specific location in the 16,777,216 hosts. Examples of Class A form username@hostname; username is networks include General Electric, IBM, your user name, logon name, or account Hewlett-Packard, Apple Computer, name or number, and hostname is the name Xerox, Digital Equipment Corporation, of the Internet Service Provider (ISP) or and MIT. All the Class A networks are in computer system you use. The hostname use, and no more are available. may consist of several parts, each separated I Class B is used for medium-sized net- from the next by a period. works. The 2 high-order bits are always See also address bus; Domain Name Ser- 10, and the remaining bits are used to de- vice; e-mail address; Internet Service Pro- fine 16,384 networks, each with as many vider; IP address; memory address. as 65,535 hosts attached. Examples of Class B networks include Microsoft and address bus The electronic channel, Exxon. All Class B networks are in use, usually from 20 to 64 lines wide, used to and no more are available. 13 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 14 Thursday, May 4, 2000 11:59 AM addressing space I Class C is for smaller networks. The 3 order bits are always 1110, and the re- high-order bits are always 110, and the re- maining 28 bits allow for more than 268 maining bits are used to define 2,097,152 million possible addresses. networks, but each network can have a I Class E is reserved for experimental pur- maximum of only 254 hosts. Class C net- poses. The first four bits in the address are works are still available. always 1111. I Class D is a special multicast address and See also Classless Inter-Domain Routing; cannot be used for networks. The 4 high- IP address; subnet mask. IP ADDRESS STRUCTURE addressing space The amount of RAM node on the same network when it knows available to the operating system running only the target’s logical or IP address. on a server. Under ARP, a network interface card con- address mask See subnet mask. tains a table (known as the address resolu- tion cache) that maps logical addresses to Address Resolution Protocol Abbrevi- the hardware addresses of nodes on the net- ated ARP. A protocol within TCP/IP work. When a node needs to send a packet, (Transmission Control Protocol/Internet it first checks the address resolution cache Protocol) and AppleTalk networks that al- to see if the physical address information is lows a host to find the physical address of a already present. If so, that address is used, and network traffic is reduced; otherwise, a 14 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 15 Thursday, May 4, 2000 11:59 AM Advanced Communications Service normal ARP request is made to determine The Administrator account cannot be delet- the address. ed, but it can be renamed, which is probably See also IP address. a good security policy. See also permissions. address translation gateway Abbrevi- ated ATG. A function in Cisco DECnet ADMIN object A NetWare Directory routing software capable of establishing a Services User object, created during the in- user-specified address translation mecha- stallation of NetWare, that has special priv- nism for certain selected nodes on the net- ileges, including the supervisory rights to work. create and manage other objects. adjacency A term describing the rela- ADMIN has Supervisor rights and can, tionship formed between certain neighbor- therefore, manage the NetWare Directory ing routers for the purpose of swapping Services tree and add or delete Directory routing information. Adjacency is based on objects. the use of a common network segment. ADSI See Active Directory Service administrative alerts In Windows Interface. 2000, informational messages sent to spe- ADSL See Asymmetric Digital Sub- cific accounts, groups, or computers to an- scriber Line. nounce security events, impending shutdown due to loss of server power, per- ADUC See Active Directory Users and formance problems, and printer errors. Computers. When a server generates an administrative Advanced Communications alert, the appropriate message is sent to a Function Abbreviated ACF. A set of predefined list of users and computers. program packages from IBM that allows See also Alerter service. computer resources to be shared over communications links using the concepts of administrative distance A term used SAA (Systems Application Architecture). by Cisco Systems, Inc., to express the integrity of a routing-information source. For example, ACF/TCAM (Advanced Com- Administrative distance is expressed as a munications Functions/Telecommunica- value in the range 0 through 255; the higher tions Access Method) and ACF/VTAM the value, the lower the quality of the rout- (Advanced Communications Functions/Vir- ing information. tual Telecommunications Access Method) allow the interconnection of two or more do- Administrator account In Microsoft mains into one multiple-domain network. Windows 2000, a special account with the maximum authority and permissions that Advanced Communications Service can assign any permission to any user or Abbreviated ACS. A large data-communi- group. cations network established by AT&T. 15 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 16 Thursday, May 4, 2000 11:59 AM Advanced Configuration and Power Interface Advanced Configuration and Power AMD386, AMD486, AMDK5, and the Interface Abbreviated ACPI. An inter- AMDK6. face specification developed by Intel, Mi- For more information about AMD, see crosoft, and Toshiba for controlling power www.amd.com. use on the PC and all other devices at- See also Cyrix; Intel Corporation; Pentium; tached to the system. A BIOS-level hard- Pentium II; Pentium III. ware specification, ACPI depends on specific hardware that allows the operat- Advanced Mobile Phone Service Ab- ing system to direct power management breviated AMPS. Currently the cellular and system configuration. telephone standard in the United States; an See also Advanced Power Management. analog, cellular communications system de- veloped by AT&T. AMPS uses frequency- Advanced Data Communications Con- division multiplexing (FDM) and operates trol Procedures Abbreviated ADCCP. in the 825 to 890MHz range. A bit-oriented, link-layer, ANSI-standard See also Cellular Digital Packet Data. communications protocol. See also High-level Data Link Control. Advanced Peer-to-Peer Internet- working An SNA routing scheme pro- Advanced Interactive Executive posed by Cisco Systems and eventually Abbreviated AIX. A version of Unix from abandoned. IBM that runs on its RS/6000 workstations and on minicomputers and mainframes. Advanced Peer-to-Peer Networking Abbreviated APPN. IBM’s SNA (Systems Although AIX is based on Unix System V Network Architecture) protocol, based on Release 3, it contains many of the features APPC (Advanced Program-to-Program available in System V Release 4, is Communications). APPN allows nodes on POSIX-compliant, and meets the Trusted the network to interact without a main- Computer Base (TCB) Level C2 security. frame host computer and implements dy- One of the major enhancements of AIX is namic network directories and dynamic Visual Systems Management (VSM), a routing in an SNA network. graphical interface into the older Systems APPN can run over a variety of network me- Management Interface Tool (SMIT). VSM dia, including Ethernet, token ring, FDDI, contains four main elements: Print Manag- ISDN, X.25, SDLC, and higher-speed links er, Device Manager, Storage Manager, and such as B-ISDN or ATM. Users and Groups Manager. See also Asynchronous Transfer Mode; Advanced Micro Devices, Inc. Abbre- Customer Information Control System; viated AMD. The fifth largest manufactur- Systems Network Architecture. er of integrated circuits, flash memory, and microprocessors, specializing in clones of Advanced Power Management Ab- Intel’s popular PC chips, including the breviated APM. An API specification from 16 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 17 Thursday, May 4, 2000 11:59 AM Aggregate Route-Based IP Switching Microsoft and Intel intended to monitor Ware uses the Service Advertising Protocol and extend battery life on a laptop comput- (SAP) for this purpose. er by shutting down certain system compo- AFP See AppleTalk Filing Protocol. nents after a period of inactivity. See also Advanced Configuration and AFS See Andrews File System. Power Interface. aftermarket The market for related hardware, software, and peripheral devices Advanced Program-to-Program created by the sale of a large number of Communications Abbreviated APPC. A computers of a specific type. set of protocols developed by IBM as a part of its SNA (Systems Network Architecture), agent 1. A program that performs a task designed to allow applications running on in the background and informs the user PCs and mid-range hosts to exchange data when the task reaches a certain milestone or easily and directly with mainframes. APPC is complete. can be used over an SNA, Ethernet, X.25, 2. A program that searches through ar- or Token Ring network and is an open, chives looking for information specified by published communications protocol. the user. A good example is a spider that APPC/PC is a PC-based version of APPC searches Usenet articles. Sometimes called used over a Token Ring network. an intelligent agent. advanced run-length limited 3. In SNMP (Simple Network Manage- encoding Abbreviated ARLL. A tech- ment Protocol), a program that monitors nique used to store information on a hard network traffic. disk that increases the capacity of run- 4. In client-server applications, a program length limited (RLL) storage by more than that mediates between the client and the 25 percent and increases the data-transfer server. rate to 9Mbps. Aggregate Route-Based IP See also RLL encoding. Switching Abbreviated ARIS. A scheme from IBM used to establish switched paths Advanced Technology Attachment through networks that act as virtual cir- Abbreviated ATA. The ANSI X3T10 stan- cuits, transmitting data packets through the dard for the disk-drive interface usually network without the need to make routing known as Integrated Drive Electronics decisions at every step. ARIS uses tagging (IDE). techniques to add information to the data See also Integrated Drive Electronics. packets that can be used to guide the pack- ets through the virtual circuits based on in- advertising The process by which servic- formation already established by protocols es on a network inform other devices on the such as Open Shortest Path First (OSPF) network of their availability. Novell Net- and Border Gateway Protocol (BGP). 17 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 18 Thursday, May 4, 2000 11:59 AM AIX AIX See Advanced Interactive alpha testing The first stage in testing a Executive. new hardware or software product, usually performed by the in-house developers or alert log In Microsoft Windows 2000, a programmers. System Monitor log used to monitor See also beta testing. counters that exceed user-specified limits. When such a limit is exceeded, the event is alternative route A secondary commu- logged into the alert log. nications path to a specific destination. An See also counter log; System Monitor; alternative route is used when the primary trace log. path is not available. See also adaptive routing. Alerter service A Microsoft Windows 2000 service that warns a predefined list of alt newsgroups A set of Usenet news- users and computers of an administrative groups containing articles on controversial alert. The Alerter service is used by the subjects often considered outside the main- Server service and requires the Messenger stream. Alt is an abbreviation for alternative. service. These newsgroups were originally created See also administrative alerts; Messenger to avoid the rigorous process required to service; service. create an ordinary newsgroup. Some alt newsgroups contain valuable discussions Alias object In Novell NetWare, a leaf on subjects ranging from agriculture to object that references the original location wolves, others contains sexually explicit of an object in the directory. Using Alias ob- material, and others are just for fun. Not all jects, one object can appear in several con- ISPs and online services give access to the tainers at the same time, allowing users to complete set of alt newsgroups. locate and use the object quickly and easily. See also mailing list; moderated newsgroup; newsgroup; unmoderated See also leaf object. newsgroup. Allowed Cell Rate See Available Cell AMD See Advanced Micro Devices, Inc. Rate. American National Standards alphanumeric Consisting of letters, Institute Abbreviated ANSI. A nonprofit numbers, and sometimes special control organization of more than 1000 business characters, spaces, and other punctuation and industry groups, founded in 1918, characters. devoted to the development of voluntary See also American Standard Code for standards. Information Interchange; Extended Binary ANSI represents the United States in the In- Coded Decimal Interchange Code; ternational Organization for Standardiza- Unicode. tion (ISO) and is affiliated with CCITT. 18 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 19 Thursday, May 4, 2000 11:59 AM analog ANSI committees have developed many im- I Thick Ethernet: 12 AWG portant standards, including the following: I Thin Ethernet: 20 AWG I ANSI X3J11: Standard for the C pro- See also cabling standards; EIA/TIA 586; gramming language, including language Type 1–9 cable. semantics, syntax, execution environ- ment, and the definition of the library and America Online, Inc. Abbreviated header files. AOL. The world’s largest online service, I ANSI X3J16: Standard for the C++ pro- headquartered in Vienna, Virginia, with gramming language. more than 15 million subscribers. AOL I ANSI X3J3: Definition of the Fortran pro- provides a gateway to the Internet, as well gramming language compiler. as its own news, sports, e-mail, chat rooms, and other fee-based services. In 1997, AOL I ANSI X3.131-1986: Definition of the bought CompuServe, and in 1998, SCSI standard. The X3T9.2 standard con- Netscape Communications. tains the extensions for SCSI-2. For more information about America On- I ANSI X3T9.5: The working group for the line, see www.aol.com. FDDI definition. ampersand (&) 1. In Unix, a command American Standard Code for Informa- suffix used to indicate that the preceding tion Interchange Abbreviated ASCII, command should be run in the background. pronounced “as-kee.” A standard coding scheme that assigns numeric values to let- 2. In Unix, a root user command used to ters, numbers, punctuation characters, and start a daemon that is to keep running after control characters to achieve compatibility logout. among different computers and peripheral 3. In HTML, a special character entry in a devices. In ASCII, each character is repre- document. sented by a unique integer value in the range See also daemon; HyperText Markup 0 through 255. See Appendix C. Language. See also ASCII extended character set; ASCII file; ASCII standard character set; AMPS See Advanced Mobile Phone double-byte character set; Extended Service. Binary Coded Decimal Interchange Code; Unicode. analog Describes any device that repre- sents changing values by a continuously American Wire Gauge Abbreviated variable physical property, such as a volt- AWG. A measurement system that specifies age in a circuit. Analog often refers to trans- copper wire by thickness; as thickness mission methods developed to transmit increases, the AWG number decreases. voice signals rather than high-speed digital Some common conductor gauges are: signals. I RS-232-C: 22 or 24 AWG 19 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 20 Thursday, May 4, 2000 11:59 AM Andrews File System Andrews File System Abbreviated You cannot use anonymous FTP with every AFS. A protocol developed at Carnegie computer on the Internet, only with those Mellon University; used to share remote systems set up to offer the service. The sys- files across systems using TCP/IP. tem administrator decides which files and directories will be open to public access, AFS has certain advantages over NFS in and the rest of the system is considered off that it only allows users to access files linked to AFS rather than giving access to limits and cannot be accessed by anony- all files, it has a built-in cache that helps to mous FTP users. Some sites only allow you reduce the demands made on the system, to download files; as a security precaution, and system administrators can allocate disk you are not allowed to upload files. space on the fly as required. See also File Transfer Protocol; Telnet. See also Distributed File System; Network File System; Transmission Control Proto- anonymous posting In a Usenet news- col/Internet Protocol. group, a public message posted via an anon- ymous server in order to conceal the angle brackets The less-than (<) and identity of the original sender. greater-than (>) symbols used to identify a anonymous remailer See anonymous tag in an HTML document. server. Also used to identify the return address in an e-mail message header. anonymous server A special Usenet service that removes from a Usenet post all See also HyperText Markup header information that could identify the Language; tag. original sender and then forwards the mes- ANI See automatic number sage to its final destination. If you use an identification. anonymous server, be sure to remove your signature from the end of the message; not anonymous FTP A method used to ac- all anonymous servers look for and then cess an Internet computer that does not re- strip a signature. Also known as an anony- quire you to have an account on the target mous remailer. computer system. Simply log on to the In- ternet computer with the user name anon- ANSI See American National Standards ymous, and use your e-mail address as your Institute. password. This access method was original- answer mode A function that allows a ly provided as a courtesy so that system ad- modem to answer an incoming call, detect ministrators could see who had logged on the protocol being used by the calling mo- to their systems, but now it is often required dem, and synchronize with that protocol. to gain access to an Internet computer that has FTP service. See also auto-answer; auto-dial. 20 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 21 Thursday, May 4, 2000 11:59 AM Apple Computer, Inc. antivirus program A program that de- Apache dominates the Web because of its tects or eliminates a computer virus. Some low cost, excellent performance, good scal- antivirus programs can detect suspicious ability, and great flexibility. Don’t expect activity on your computer as it happens; easy graphical configuration programs and others must be run periodically as part of hypertext help; you’ll get the command line your normal housekeeping activities. and the man pages instead, so it certainly helps to have staff with Unix experience. An antivirus program locates and identifies a virus by looking for characteristic pat- Apache Server is available as part of the Red terns or suspicious activity in the system, Hat Software Linux distribution, which also provides developers with full support such as unexpected disk access or .EXE files for CGI, Perl, Tcl, a C or C++ compiler, an changing in some unusual way. It recogniz- Apache server API, and a SQL database. es the virus by comparing information from the system against a database of known vi- For more information on Apache Server, ruses, which is kept on disk. see The Apache Group Web site at www.apache.org. Be sure you test an antivirus program care- See also Linux; Red Hat Software. fully on your network before you employ it everywhere; some programs impose an API See application programming enormous overhead on normal network interface. operations. APM See Advanced Power See also file-infecting virus; macro virus; Management. multipart virus; polymorphic virus; stealth virus; Trojan Horse; vaccine; virus. app See application. APPC See Advanced Program-to-Pro- AnyNet A family of gateway products gram Communications. from IBM used to integrate SNA, TCP/IP, and NetBIOS networks with products run- APPI See Advanced Peer-to-Peer Inter- ning on IBM’s AIX/6000, OS/2, and OS/ networking. 400 and with Microsoft Windows. Apple Computer, Inc. Manufacturer of the successful Macintosh and Quadra series AOL See America Online, Inc. of computers based on Motorola chips. The Apache HTTP Server A freeware Web company was founded by Steve Wozniak server, supported by the Unix community, and Steve Jobs in a garage on April 1, 1976. in use on almost half of the Web sites on the In 1993, Apple entered the consumer elec- Internet. So called because the original uni- tronics marketplace with a personal digital versity-lab software was patched with new assistant known as Newton, combining features and fixes until it became known as fax, electronic mail, and other functions “a patchy server.” into a unit small enough to fit into a pocket. 21 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 22 Thursday, May 4, 2000 11:59 AM Apple Desktop Bus In 1994, Apple launched a new series of AppleTalk An Apple Macintosh network computers called the Power Macintosh (or protocol, based on the OSI Reference Mod- Power Mac), based on the PowerPC, capa- el, which gives every Macintosh network- ble of running either the Macintosh operat- ing capabilities. AppleTalk can run under ing system or Windows programs under several network operating systems, includ- software emulation. ing Apple Computer’s AppleShare, Novell NetWare for the Macintosh, and TOPS Apple always kept the architecture of the Mac proprietary, a move that has cost the from Sun Microsystems. company considerable market share; never- AppleTalk includes specifications for the theless, Apple has always had a strong fol- data-link layer as LocalTalk, EtherTalk, lowing among musicians and graphical FDDI-Talk, or TokenTalk, and the network designers. layer as Datagram Delivery Protocol. The In 1997, Steve Jobs rejoined Apple and, af- transport layer contains four protocols: ter realigning Apple’s product line, led the I Routing Table Maintenance Protocol development and launch of the popular and (RTMP) capable Internet-ready iMac computer. I AppleTalk Echo Protocol (AEP) For more information on Apple Computer, I AppleTalk Transaction Protocol (ATP) Inc., see www.apple.com. I Name Binding Protocol (NBP) Apple Desktop Bus A serial communi- cations link that connects low-speed input The session layer includes devices, such as a mouse or a keyboard, to I AppleTalk Data Stream Protocol (ADSP) the computer on the Macintosh SE, II, IIx, IIcx, and SE/30. I AppleTalk Session Protocol (ASP) Light pens, trackballs, and drawing tablets I Printer Access Protocol (PAP) may also be connected via the Apple Desk- I Zone Information Protocol (ZIP) top Bus. Most Apple Desktop Bus devices The presentation layer adds the AppleTalk allow one device to be daisy-chained to the Filing Protocol (AFP) for access to remote next, up to a maximum of 16 devices. files on shared disks. Apple Macintosh See Macintosh. AppleTalk Filing Protocol Abbreviat- AppleShare Network software from ed AFP. AFP is located in the presentation Apple Computer that requires a dedicated and application layers of the AppleTalk Macintosh computer acting as a central- protocol stack. AFP lets users access remote ized server and includes both server and files as though they were local, as well as workstation software. AppleShare uses the providing security features that can restrict AppleTalk Filing Protocol (AFP). user access to certain files. 22 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 23 Thursday, May 4, 2000 11:59 AM application APPLETALK PROTOCOL STACK application Abbreviated app, or if the network applications. Stand-alone applica- application is a small one, it is referred to as tions run from the hard disk in an indepen- an applet. A computer program designed to dent computer, so only one user at a time can perform a specific task, such as accounting, access the application. Network applica- scientific analysis, word processing, or tions run on networked computers and can desktop publishing. be shared by many users. Advanced applica- tions such as groupware and e-mail allow In general, applications can be distinguished communications between network users. from system software, system utilities, and computer language compilers, and they can See also application metering; client/ be categorized as either stand-alone or server architecture; LAN-aware. 23 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 24 Thursday, May 4, 2000 11:59 AM Application Binary Interface Application Binary Interface Abbrevi- application log In Microsoft Windows ated ABI. A specification that aims to ensure 2000, a system log that contains events gen- binary compatibility between applications erated by applications or by alert logs. You running on the same family of processors or can use the Event Viewer to display the con- CPUs using Unix System V Release 4. tents of the application log. Applications developed using ABI can run See also Event Viewer; security log; sys- on hardware from different manufacturers tem log. without being recompiled; any system calls application metering The process of needed for specific hardware are main- counting the number of executions of the tained in libraries. copies of an application in use on the net- The specification was originally developed work at any given time and ensuring that by AT&T and Sun Microsystems and in- the number does not exceed preset limits. cludes a test and verification suite used to Application metering is usually performed determine if a system complies with the by a network management application run- standard. ning on the file server. Most application See also application programming metering software will allow only a certain interface. number of copies (usually that number specified in the application software li- application layer The seventh, or high- cense) of an application to run at any one est, layer in the OSI Reference Model for time and will send a message to any users computer-to-computer communications. who try to exceed this limit. This layer uses services provided by the See also concurrent license. lower layers but is completely insulated from the details of the network hardware. It Application object In Novell Directory describes how applications interact with Services (NDS), a leaf object that represents the network operating system, including a network application in a NetWare Direc- database management, electronic mail, and tory tree. terminal emulation programs. See also Computer object; container ob- See also OSI Reference Model. ject; leaf object; Novell Directory Services. application-level filter A category of application programming interface firewall that provides a high degree of secu- Abbreviated API. The complete set of all rity but at the cost of lower speed and great- operating system functions that an applica- er complexity. Typical application-level tion can use to perform such tasks as man- filters can provide proxy services for appli- aging files and displaying information. cations and protocols such as Telnet, FTP, An API provides a standard way to write an HTTP, and SMTP. application, and it also describes how the See also firewall; packet-level filter; state- application should use the functions it pro- less filter. vides. Using an API is quicker and easier 24 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 25 Thursday, May 4, 2000 11:59 AM archive file than developing functions from scratch and Archie A system used on the Internet to helps to ensure some level of consistency locate files available by anonymous FTP. among all the applications developed for a Once a week, special programs connect to specific operating system. all the known anonymous FTP sites on the Internet and collect a complete listing of all In operating systems that support a graphi- the publicly available files. This listing of cal user interface, the API also defines func- files is kept in an Internet Archive Database, tions to support windows, icons, drop-down and when you ask Archie to look for a file, menus, and other components of the inter- it searches this database rather than the face. In network operating systems, an API whole Internet; you then use anonymous defines a standard method that applications FTP to retrieve the file. can use to take advantage of all the network features. See also anonymous FTP. application server A special-purpose architecture 1. The overall design and file server that is optimized for a specific construction of all or part of a computer, task, such as communications or a database particularly the processor hardware and the application, and that uses higher-end hard- size and ordering sequence of its bytes. ware than a typical file server. 2. The overall design of software, including See also superserver. interfaces to other software, the operating system, and to the network. application-specific integrated See also client/server architecture; closed circuit Abbreviated ASIC. A computer architecture; complex instruction set com- chip developed for a specific purpose, de- puting; open architecture; reduced instruc- signed by incorporating standard cells from tion set computing. a library rather than created from scratch. Also known as gate arrays, ASICs are found archive 1. To transfer files to some form in all sorts of appliances, including mo- of long-term storage, such as magnetic tape dems, security systems, digital cameras, and or large-capacity disk, when the files are no even microwave ovens and automobiles. longer needed regularly but must be main- tained for periodic reference. APPN See Advanced Peer-to-Peer Net- 2. On the Internet, a site containing a working. collection of files available via anonymous FTP. ARB See Area Border router. 3. A compressed file. arbitration The set of rules used to man- archive file A single file that contains one age competing demands for a computer or more files or directories that may have resource, such as memory or peripheral de- been compressed to save space. Archives are vices, made by multiple processes or users. often used as a way to transport large num- See also contention. bers of related files across the Internet. 25 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 26 Thursday, May 4, 2000 11:59 AM ARCNet An archive file created under Unix may have ARIS See Aggregate Route-Based IP the filename extension .TAR (for tape ar- Switching. chive), .GZ (for gzip), or .Z (for compress or ARLL See advanced run-length limited pack). Those created in Windows may have encoding. the filename extension .ZIP from the PKZIP or WinZip programs. Archive files created ARP See Address Resolution Protocol. on a Macintosh will have the filename exten- sion .SAE or .SIT from the StuffIt program. ARPAnet Acronym for Advanced Re- search Projects Agency Network. A re- An Internet host that provides access to search network funded by the Defense large numbers of archive files is known as Advanced Research Projects Agency an archive site. (DARPA) to link universities and govern- ment research agencies, originally built by ARCNet Acronym for Attached Resourc- BBN, Inc., in 1969. It was the backbone es Computing Network. A network avail- for the now huge Internet. TCP/IP proto- able from the Datapoint Corporation and cols were pioneered on ARPAnet. In 1983, other vendors that can connect a wide vari- the military communications portion was ety of PCs and workstations (up to a maxi- split off into the MILnet. mum of 255) on coaxial, twisted-pair, or fiber-optic cable. ARCnet uses a proprietary article An e-mail message posted to one token-passing access method at speeds of of the Usenet newsgroups, accessible by 2.5Mbps. ARCNet Plus is Datapoint’s pro- anyone with a newsreader and a connection prietary product that runs at 20Mbps. to the Internet. Also called a post. ARCNet was popular for smaller networks, See also newsreader. because it is relatively easy to set up and to operate and also because the components AS/400 A series of mid-range mini- are inexpensive and widely available. These computers from IBM, first introduced in days, however, it is showing its age and is 1988, that replaces the System/36 and Sys- no longer sold by the major vendors. tem/38 series of computers. The AS/400 can serve in a wide variety of network con- See also Token Ring network. figurations: as a host or an intermediate node to other AS/400 and System/3x com- Area Border router Abbreviated ARB. puters, as a remote system to System/370- In an internetwork that uses link state rout- controlled networks, or as a network serv- ing protocols such as Open Shortest Path er to a group of PCs. First (OSPF) protocols, a router that has at least one connection to another router in a ASBR See Autonomous System Bor- different part of the internetwork. Also der router. known as a Border router. Ascend Certified Technical Expert See also Autonomous System Border Abbreviated ACTE. A certification scheme router; Open Shortest Path First. from Ascend Communications, Inc., aimed 26 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 27 Thursday, May 4, 2000 11:59 AM ASP at technical professionals with experience standard character set; double-byte char- in installing, configuring, and trouble- acter set; Extended Binary Coded Decimal shooting Ascend remote-access products. Interchange Code; Unicode. Two written exams, the Networking and Telecommunications exam, and the Re- ASCII file A file that contains only text mote Access exam, are followed by a hands- characters from the ASCII character set. An on lab test administered at Ascend’s head- ASCII file can include letters, numbers, and quarters in Alameda, CA. punctuation symbols, but does not contain any hidden text-formatting codes. Also Ascend Communications, Inc. A lead- known as a text file or an ASCII text file. ing provider of solutions for telecommuni- cations carriers, ISPs, and corporate See also American Standard Code for In- customers, Ascend manufactures products formation Interchange; ASCII extended for remote access, for wide area network- character set; ASCII standard character set; ing, and for linking telephone switches, net- binary file. work connections, and videoconferencing ASCII standard character set A char- facilities to phone company networks. acter set that consists of the first 128 (from Ascend recently acquired Cascade Commu- 0 through 127) ASCII characters. The val- nications, establishing the company as one ues 0 through 31 are used for nonprinting of the largest suppliers of frame-relay and control codes (see Appendix C), and the ATM equipment. In 1999, Ascend was range 32 through 127 is used to represent bought by Lucent Technologies. the letters of the alphabet and common For more information on Ascend, see punctuation symbols. The entire set from 0 www.ascend.com. through 127 is referred to as the standard ASCII character set. All computers that use ASCII See American Standard Code for ASCII can understand the standard ASCII Information Interchange. character set. ASCII extended character set The sec- See also American Standard Code for In- ond group of characters, from 128 through formation Interchange; ASCII file; ASCII ex- 255, in the ASCII character set. The extend- tended character set; double-byte ed ASCII character set is assigned variable character set; Extended Binary Coded Dec- sets of characters by computer hardware imal Interchange Code; Unicode. manufacturers and software developers, and it is not necessarily compatible between dif- ASCII text file See ASCII file. ferent computers. The IBM extended char- acter set used in the PC (see Appendix C) ASE See Accredited Systems Engineer. includes mathematics symbols and charac- ASIC See application-specific ters from the PC line-drawing set. integrated circuit. See also American Standard Code for In- formation Interchange; ASCII file; ASCII ASP See Active Server Pages. 27 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 28 Thursday, May 4, 2000 11:59 AM assembly language assembly language A low-level pro- Association of Banyan Users gramming language in which each program International Abbreviated ABUI. The statement must correspond to a single ma- Banyan user group, with 1700 members chine language instruction that the proces- worldwide, concerned with all hardware sor can execute. and software related to the Banyan system, including Banyan VINES. Assembly languages are specific to a given microprocessor and, as such, are not porta- See also Banyan VINES. ble; programs written for one type of pro- cessor must be rewritten before they can be asterisk In several operating systems, used on another type of processor. you can use the asterisk (*) as a wildcard character to represent one or more un- You use assembly language for two reasons: known characters in a filename or filename I To wring as much performance out of the extension. processor as possible See also question mark; star-dot-star. I To gain access to specific characteristics of the hardware that might not be possible AST Research One of the world’s top from a higher-level language ten computer manufacturers, AST Re- search makes desktop, laptop, notebook, See also compiler; interpreter; machine and hand-held computers, as well as moni- language; microcode tors, graphics cards, and memory products. A subsidiary of Samsung Electronics Com- Associate Business Continuity pany Limited. Professional Abbreviated ABCP. A cer- tification from Disaster Recovery Institute For more information on AST Research, see International (DRII) that covers basic in- www.ast.com. formation on business continuity planning asymmetrical multiprocessing A mul- and disaster recovery. tiprocessing design in which the program- See also Certified Business Continuity mer matches a specific task to a certain Professional; Master Business Continu- processor when writing the program. ity Professional. This design makes for a much less flexible system than SMP (symmetrical multipro- Associated Accredited Systems cessing) and may result in one processor be- Engineer Abbreviated AASE. A certifica- ing overworked while another stands idle. tion from Compaq designed to evaluate and SMP allocates tasks to processors as the recognize basic knowledge of PC architec- program starts up, on the basis of current ture and operations. An AASE may choose system load and available resources. Need- to specialize in Microsoft Windows 2000 or less to say, asymmetrical multiprocessing Novell NetWare operation. systems are easier to design, code, and test See also Accredited Systems Engineer. than symmetrical multiprocessing systems. 28 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 29 Thursday, May 4, 2000 11:59 AM asynchronous transmission Asymmetric Digital Subscriber Line division multiplexing in which time slots are Abbreviated ADSL. A high-speed data allocated dynamically based on demand. transmission technology originally devel- See also time-division multiplexing. oped by Bellcore and now standardized by ANSI as T1.413. ADSL delivers high band- Asynchronous Transfer Mode Abbre- width over existing twisted-pair copper viated ATM. A method used for transmit- telephone lines. Also called Asymmetric ting voice, video, and data over high-speed Digital Subscriber Loop. LANs and WANs. ATM uses continuous bursts of fixed-length packets called cells to ADSL supports speeds in the range of 1.5 to transmit data. The basic packet consists of 9Mbps in the downstream direction (from 53 bytes, 5 of which are used for control the network to the subscriber) and supports functions and 48 for data. upstream speeds in the range of 16 Kbps to 640 Kbps; hence, the term asymmetric. ATM is a connection-oriented protocol, and two kinds of connections are possible: See also Digital Subscriber Line; High-Bit- I Permanent virtual circuits (PVCs), in Rate Digital Subscriber Line; Rate-Adaptive which connections are created manually Digital Subscriber Line; Single-Line Digi- tal Subscriber Line; Very-High-Bit-Rate I Switched virtual circuits (SVCs), in which Digital Subscriber Line. connections are made automatically Speeds of up to 2.488Gbps have been Assymetric Digital Subscriber Loop achieved in testing. ATM will find wide ac- See Assymetric Digital Subscriber Line. ceptance in the LAN and WAN arenas as a solution to integrating disparate networks asynchronous communications See over large geographical distances. Also asynchronous transmission. known as cell relay. asynchronous communications See also permanent virtual circuit; server A LAN server that allows a net- switched virtual circuit. work user to dial out of the network into asynchronous transmission A method the public switched telephone system or to of data transmission that uses start bits and access leased lines for asynchronous com- stop bits to coordinate the flow of data so munications. Asynchronous communica- that the time intervals between individual tions servers may also be called dial-in/dial- characters do not need to be equal. Parity out servers or modem servers. also may be used to check the accuracy of asynchronous time-division the data received. multiplexing Abbreviated ATDM. An See also communications parameters; asynchronous and adaptive version of time- data bits; synchronous transmission. 29 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 30 Thursday, May 4, 2000 11:59 AM ATA ASYNCHRONOUS TRANSMISSION ATA See Advanced Technology ATM Adaptation Layer Abbreviated Attachment. AAL. A service-dependent layer in Asyn- chronous Transfer Mode (ATM) that pro- AT command set A set of standard in- vides the protocol translation between structions used to activate features on a mo- ATM and the other communications servic- dem. Originally developed by Hayes es involved in a transmission. Microcomputer Products, the AT com- mand set is now used by almost all modem AAL has several service types and classes of manufacturers. operation to handle different kinds of traf- fic, depending on how data is transmitted, See also modem. the bandwidth required, and the types of ATDM See asynchronous time-division connection involved. multiplexing. See also convergence sublayer; segmen- tation and reassembly sublayer. ATG See address translation gateway. ATM LAN Emulation An Asynchro- ATM See Asynchronous Transfer Mode. nous Transfer Mode (ATM) variation that ATM25 A low-cost version of Asynchro- uses software to make the network operat- nous Transfer Mode (ATM) that runs on ing system see an ATM adapter as an Ether- Category 3 unshielded twisted-pair cable net or Token Ring adapter. and provides 25Mbps transmissions in See also IP over ATM; LAN Emulation; both directions. Multiprotocol over ATM. See also Asynchronous Transfer Mode; IP over ATM; LAN Emulation; Multiprotocol over ATM. 30 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 31 Thursday, May 4, 2000 11:59 AM AUDITCON at symbol The separating character (@) attenuation The decrease in power of a between account name and domain name in signal with increasing distance. Attenua- an Internet e-mail address. tion is measured in decibels, and it increases See also bang path. as the power of the signal decreases. The best cables (those exhibiting the least atten- AT&T The parent company of Bell Labo- uation) are fiber-optic lines, and the worst ratories, the original developers of Unix. cables are unshielded, untwisted-pair lines, For many years Bell Labs was one of the such as the silver, flat-satin cables used in two major development centers for Unix short-run telephone and modem lines. (the other being the Computer Systems Re- In a LAN, attenuation can become a prob- search Group at the University of Califor- lem when cable lengths exceed the stated nia at Berkeley), but in 1990, AT&T network specification; however, the useful formed Unix Systems Laboratories, or USL, length of a cable may be extended by the use to continue the development of Unix. In of a repeater. 1993, USL was sold to Novell, and in 1995, Novell sold the rights to SCO (Santa Cruz attribute 1. A file attribute is a tech- Operation). nique for describing access to and proper- ties of files and directories within a file See also Baby Bells; Regional Bell Operat- system. You may see the term attribute used ing Companies. interchangeably with the term property. attach To establish a connection be- 2. A screen attribute controls a character’s tween a workstation and a network file background and foreground colors, as well server; particularly, to access additional as other characteristics, such as underlining, servers after logging on to one server. reverse video, and blinking or animation. attachment See enclosure. 3. In operating systems, a characteristic that indicates whether a file is a read-only Attachment Unit Interface Abbreviat- file, a hidden file, or a system file or has ed AUI. A 15-pin socket used by some changed in some way since it was last Ethernet devices. AUI connections adapt backed up. between two different cabling types and 4. In markup languages such as HTML and work with a wide range of wiring schemes. SGML, a name-value pair within a tagged Also known as a DIX (for Digital, Intel, element that modifies certain characteris- Xerox) connector. tics of that element. attack An attempt to circumvent the se- 5. In a database record, the name or struc- curity measures in place on a network either ture of a field. to gain unauthorized access to the system or See also tag. to force a denial of service. See also brute-force attack; dictionary at- AUDITCON A Novell NetWare and In- tack; social engineering. tranetWare workstation utility that creates 31 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 32 Thursday, May 4, 2000 11:59 AM audit policy a log file to allow an independent auditor to log on and access the system in accordance verify that network transactions are accu- with the rights or permissions assigned to rate and that confidential information is se- his or her user account. cure. When auditing is enabled, an auditor See also authorization; Kerberos; pass- can track when files or directories are cre- word; user; user account. ated, deleted, modified, salvaged, moved, or renamed. Changes to security rights can authoring The process of preparing a also be tracked. multimedia presentation or a Web page. This involves not only writing the text of audit policy In Microsoft Windows the presentation or Web page, but also the 2000, the policy that defines the security production of the slides, sound, video, and events to track and report to the network graphical components. administrator. See also security log. authorization The provision of rights or permissions based on identity. Authoriza- audit trail An automatic feature of cer- tion and authentication go hand in hand in tain programs or operating systems that networking; your access to services is based creates a running record of all transactions. on your identity, and the authentication An audit trail allows you to track a piece of processes confirm that you are who you say data from the moment it enters the system you are. to the moment it leaves and to determine See also authentication. the origin of any changes to that data. auto-answer A feature of a modem auditing The process of scrutinizing net- that allows it to answer incoming calls work security-related events and transac- automatically. tions to ensure that they are accurate, particularly reviewing attempts to create, See also answer mode; dialback modem. access, and delete files and directories and auto-dial A feature of a modem that al- reviewing security violations. Records of lows it to open a telephone line and start a these events are usually stored in a security call. To auto-dial, the modem sends a series log file, which can only be examined by us- of pulses or tones that represent a stored ers with special permissions. telephone number. AUI See Attachment Unit Interface. See also callback modem. authentication In a network operating AUTOEXEC.BAT A contraction of Au- system or multiuser system, the process that tomatically Executed Batch. A special validates a user’s logon information. MS-DOS batch file, located in the root di- Authentication may involve comparing the rectory of the startup disk, that runs auto- user name and password to a list of autho- matically every time you start or restart rized users. If a match is found, the user can your computer. The commands contained 32 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 33 Thursday, May 4, 2000 11:59 AM Available Cell Rate in AUTOEXEC.BAT are executed one by tified. ANI is often associated with ISDN one, just as if you typed them at the system and is sometimes known as caller ID. prompt. An AUTOEXEC.BAT file can be automatic rollback In a Novell Net- used to load hardware device drivers, set Ware network, a feature of the Transaction the system prompt, change the default Tracking System (TTS) that abandons the drive to the first network drive, and log the current transaction and returns a database user in to the file server. to its original condition if the network fails In OS/2, you can select any batch file to be in the middle of a transaction. Automatic used as AUTOEXEC.BAT for a specific rollback prevents the database from being MS-DOS session, so you can tailor specific corrupted by information from incomplete environments for separate MS-DOS sessions, transactions. each using a different AUTOEXEC.BAT file. See also backing out. See also AUTOEXEC.NCF; boot; bootstrap; CONFIG.SYS. Autonomous System Border router Abbreviated ASBR. In an internetwork that AUTOEXEC.NCF A Novell NetWare uses link state routing protocols such as batch file usually located on the NetWare Open Shortest Path First (OSPF) protocols, partition of the server’s hard disk, used to a router that has at least one connection set the NetWare operating system configu- to a router in an external network. ration. AUTOEXEC.NCF loads the LAN See also Area Border router; Open Short- drivers, the NLMs, and the settings for the est Path First. network interface boards and then binds the protocols to the installed drivers. AutoPlay A feature of Microsoft Win- dows that automatically executes an appli- Automatic Client Upgrade A mecha- cation from a CD-ROM or automatically nism used to upgrade Novell client software plays an audio CD when the disk is inserted during the logon process by executing four into the CD-ROM drive. separate programs called by the logon script. Automatic Client Upgrade can be Available Bit Rate A Type 3 or Type 4 very useful when all client workstations use Asynchronous Transfer Mode Adaption standard configurations. Layer (AAL) service designed for non–time- critical applications such as LAN emulation automatic forwarding A feature of and LAN internetworking. many e-mail programs that automatically retransmits incoming messages to another See also Constant Bit Rate; Unspecified Bit e-mail address. Rate; Variable Bit Rate. automatic number identification Ab- Available Cell Rate Abbreviated ACR. breviated ANI. A method of passing a call- A measure of the bandwidth in Asynchro- er’s telephone number over the network to nous Transfer Mode (ATM) networks. The the recipient so that the caller can be iden- ACR value represents the number of ATM 33 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 34 Thursday, May 4, 2000 11:59 AM avatar cells available or allowed per second for a avatar 1. In Unix, another name for the specific quality of service (QoS) class. superuser account; an alternative to the Available Cell Rate is also known as Al- name root. lowed Cell Rate. 2. A visual representation of a user in a See also Asynchronous Transfer Mode; shared virtual-reality environment. Minimum Cell Rate; Peak Cell Rate; Sus- tainable Cell Rate. AWG See American Wire Gauge. 34 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 35 Thursday, May 4, 2000 11:59 AM back-end system B Baan Advanced Certification Abbrevi- See also Bell Labs. ated BAC. A certification from Baan avail- able in four specialties covering the Baan BAC See Baan Advanced Certification. IV suite of products: Enterprise Logistics, backbone That portion of the network Enterprise Finance, Enterprise Tools, that manages the bulk of the traffic. The and Enterprise Modeler. backbone may connect several locations or See also Baan Basic Certification. buildings, and other, smaller networks may be attached to it. The backbone often uses Baan Basic Certification Abbreviated a higher-speed protocol than the individual BBC. A certification from Baan designed to LAN segments. evaluate basic proficiency with the Baan IV suite of products; a prerequisite qualifica- back-end processor A secondary pro- tion to taking the Baan Advanced Certifica- cessor that performs one specialized task tion exams. very effectively, freeing the main processor for other, more important work. See also Baan Advanced Certification. back-end system The server part of a Baan Company A leading provider of client/server system that runs on one or enterprise and inter-enterprise business more file servers and provides services to software used for managing finance, man- the front-end applications running on net- ufacturing, inventory, distribution, trans- worked workstations. The back-end system portation, and administrative functions for accepts query requests sent from a front- large companies. end application, processes those requests, For more information on Baan, see and returns the results to the workstation. www2.baan.com. Back-end systems may be PC-based serv- Baby Bells A slang term for the 22 Re- ers, superservers, midrange systems, or gional Bell Operating Companies (RBOC), mainframes. formed when AT&T was broken up in 1984. See also client/server architecture. 35 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 36 Thursday, May 4, 2000 11:59 AM background BACKBONE background 1. On a computer screen, can print a document while still accepting the color on which characters are displayed; input from the keyboard. In older systems, for example, white characters may appear a process spends its entire existence in either on a blue background. the background or the foreground; in newer systems, you can change the processing en- 2. In an operating system, a process that vironment and move foreground programs runs in the background generally runs at a into the background, and vice versa. lower level of priority than a foreground See also ampersand; foreground; task and does not accept input from the us- multitasking. er. Only multitasking operating systems support true background and foreground background authentication The pro- processing, but some applications can mim- cess used to give a workstation access to a ic it. For example, many word processors particular server. For example, in Novell 36 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 37 Thursday, May 4, 2000 11:59 AM backup NetWare, password authentication uses a completely, taking all your work with public key encryption scheme to protect them. If this failure occurs, you can reload password information before it is transmit- your files and directories from the backup ted over the network. All this activity takes copy. A backup is your insurance against place in the background, and all the user disk failure affecting the thousands or has to do is enter his or her password. possibly tens of thousands of files you might have on your file server. background noise Any unwanted sig- nal that enters a line, channel, or circuit; for I Protection against accidental deletion of example, electrical interference on a tele- files or directories. Again, if you mistak- phone circuit. enly delete a file or directory, you can re- trieve a copy from your last backup. See also noise. I Protection against the new version of soft- backing out The process of abandoning ware you are about to install not working the current transaction and returning a da- to your expectations; make a backup be- tabase to its original condition if the net- fore installing new software. work fails during the transaction. This I As an archive at the end of a project, when process prevents the database from being a person leaves your company, or at the corrupted by information from the incom- end of a financial period such as year-end plete transaction. close. See also automatic rollback; Transaction Your decision when or how often to make Tracking System. a backup depends on how frequently im- portant data on your system changes. If you backlink In Novell Directory Services, an rely on certain files always being available attribute used by a directory to indicate the on your system, it is crucial that you make external references to a property. regular, consistent backups. Here are some backslash 1. In MS-DOS, OS/2, and backup tips: other operating systems, you must use the I Keep multiple copies; redundancy should backslash character () to separate directory be a part of your backup plan. or subdirectory names in a path statement I Test your backups to make sure they are or when changing to another directory. what you think they are before you bring 2. A shorthand name for the root directory. the server into service, and make sure you Sometimes called the reverse slash or can reload the information you need. backslant. I Store your backups in a secure off-site lo- See also slash. cation; do not leave them right next to the computer (if the computer is damaged by backup An up-to-date copy of all your an accident, the backup may be damaged files. You make a backup for several reasons: as well). I Insurance against possible hard-disk or I Replace your backup media on a regular file-server failure. Hard disks often fail basis. 37 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 38 Thursday, May 4, 2000 11:59 AM backup browser I Consider making incremental backups of See also disk duplexing; disk mirroring; full critical data at more frequent intervals. backup; incremental backup; tape car- It all comes down to one very simple rule: tridge; tape drive. back up all the files that you cannot afford backward compatibility Full compati- to lose. Do it now. bility with earlier versions of the same ap- See also archive; differential backup; disk plication or computer system. duplexing; disk mirroring; full backup; in- cremental backup. Backward Error Correction Abbreviat- ed BEC. An error-correction method in backup browser In Microsoft Windows which an error can be detected by the recip- 2000 Server, a computer that maintains a ient, which immediately requests a retrans- list of computers and services available on mission of the affected data. the network. This list is provided by the See also error detection and correction. master browser and distributed to a work- group or a domain by the backup browser. BACP See Bandwidth Allocation Con- See also browser; master browser. trol Protocol. bad sector An area on a hard disk or backup domain controller In Micro- floppy disk that cannot be used to store soft Windows NT, a server containing ac- data because of a manufacturing defect or curate replications of the security and user accidental damage. databases. The operating system will find, mark, and The backup domain controller receives a isolate bad sectors. Almost all hard disks copy of the domain’s directory database, have some bad sectors, often listed in the containing all the account and security infor- bad track table. Usually, bad sectors are a mation for the domain, from the primary do- result of the manufacturing process and not main controller. This copy is periodically a concern; the operating system will mark synchronized with the original master data- them as bad, and you will never even know base. A domain can contain several backup they are there. domain controllers. bad track table A list of the defective ar- See also domain controller; primary do- eas on a hard disk, usually determined dur- main controller. ing final testing of the disk at the factory. backup program An application that Some disk-preparation programs ask you you use to make archive or backup copies of to enter information from this list to reduce important data files. the time that a low-level format takes to prepare the disk for use by the operating Most operating systems offer commands system. for making backups, but many are limited in capability. The most cost-effective back- balun A contraction of balanced up programs are from third-party vendors. unbalanced. A small device used to connect 38 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 39 Thursday, May 4, 2000 11:59 AM Banyan VINES a balanced line (such as a twisted-pair bandwidth reservation A technique cable) to an unbalanced line (such as a used to reserve channel capacity for special coaxial cable). The balun matches time-sensitive transmissions such as impedances between the two media. videoconferencing and real-time audio transmissions. bandwidth 1. In communications, the difference between the highest and lowest bandwidth throttling A feature in some frequencies available for transmission in Web server software that allows the system any given range. administrator to control or alter the pro- 2. In networking, the transmission capaci- portions of bandwidth available to the ser- ty of a computer or a communications vices that the server provides. channel, stated in megabits per second bang A name given in the Unix and Inter- (Mbps). For example, FDDI (Fiber Distrib- net worlds to the exclamation point (!) uted Data Interface) has a bandwidth of character; also known as pling in the United 100Mbps. To relate this to a real-world ex- Kingdom. ample, a complete page of text, in English, See also bang path. is approximately 16,000 bits. Bandwidth Allocation Control bang path An old-style uucp e-mail ad- Protocol Abbreviated BACP. A pro- dress that uses exclamation points to sepa- posed Internet protocol designed to manage rate the sequence of computer names a combination of dial-up links, usually over needed to get to the addressee. ISDN connections. Bang paths list addresses—general to spe- BACP provides bandwidth on demand and cific—from left to right, which is the reverse can combine two or more circuits into a sin- of the sequence used by other addressing gle circuit with a higher data rate. schemes. See also bandwidth on demand. See also at symbol; domain name; e-mail address; uucp. bandwidth on demand A technique that allows the user to add additional band- Banyan Systems, Inc. A leading pro- width as the application requires it. vider of enterprise network products, in- cluding the Banyan VINES network Most network traffic does not flow in steady operating system, products based on the and easily predictable streams, but in short Banyan StreetTalk Directory, and Beyond- bursts, separated by longer periods of inac- Mail messaging technologies. tivity. This pattern makes it difficult to pre- dict peak loads. Bandwidth on demand is For more information on Banyan, see useful for applications such as backups and www.banyan.com. videoconferencing and allows the user to pay Banyan VINES A network operating sys- for only the amount of bandwidth used. tem from Banyan Systems. VINES (a con- See also virtual data network. traction of Virtual Networking Software) is 39 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 40 Thursday, May 4, 2000 11:59 AM Banyan VINES based on a special version of the Unix Sys- different LAN segments. A complete set of tem V operating system. network management tools is also available. The following illustration shows the internal Workstations can run MS-DOS, Microsoft organization of VINES. The Unix layer is Windows, Unix, or OS/2, and they can store hidden from view by VINES and is not avail- native-form files on the server. Macintosh able for other applications. VINES provides computers can also attach to the network. all server functions, including those of a com- VINES offers special support for very large munications/modem server, and offers many LANs and WANs with multiple file servers. options for connecting to minicomputers, VINES also allows PCs that support multi- mainframes, and other network file servers. ple processors to use multiprocessing to di- VINES automatically manages protocol vide the file-server processing load. binding and translations required between See also Enterprise Network Services; the network interface cards for routing to StreetTalk. BANYAN VINES 40 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 41 Thursday, May 4, 2000 11:59 AM Basic Rate ISDN base 10 radix See decimal. information about the most active users and their applications. base64 An encoding scheme used by MIME-compliant mail systems to convert Bash In Unix, a popular command inter- binary files into a text format that can be preter. Bash, the Bourne-Again Shell, was processed and sent as e-mail. first released in 1989 by Brian Fox and Chet Ramey, as part of the Free Software Foun- See also binary file; Multipurpose Internet dation GNU Project. Mail Extension. Bash provides features found in the other baseband modem See line driver. Unix shells, particularly the Bourne shell, the C shell, and the Korn shell, and includes baseband network A technique for Bourne shell syntax, redirection and quot- transmitting signals as direct-current pulses ing, C-shell command-line editing and tilde rather than as modulated signals. The entire expansion, job control, and command his- bandwidth of the transmission medium is tory. Bash also includes built-in commands used by a single digital signal, so computers and variables, as well as aliases from the in a baseband network can transmit only Korn shell. when the channel is not busy. However, the See also Bourne shell; C shell; Korn shell; network can use techniques such as multi- Linux; Unix shell. plexing to allow channel sharing. A baseband network can operate over rela- basic disk In Microsoft Windows 2000 tively short distances (up to 2 miles if net- Server, a normal hard disk, available from work traffic is light) at speeds from 50Kbps any operating system, that uses primary to 100Mbps. Ethernet, AppleTalk, and and extended partitions to divide the avail- most PC local-area networks (LANs) use able space into logical units. baseband techniques. See also dynamic disk. See also bandwidth; broadband network; Basic Rate ISDN Abbreviated BRI. An frequency-division multiplexing; statistical ISDN service that offers two 64Kbps B multiplexing; time-division multiplexing. channels used for data transfer and one 16Kbps D channel used for signaling and baseline The process of determining and control information. documenting network throughput and oth- er performance information when the net- Each B channel can carry a single digital work is operating under what is considered voice call or can be used as a data channel; a normal load. Measured performance the B channels can also be combined into a characteristics might include error-rate single 128Kbps data channel. and data-transfer information, along with See also 23B+D; 2B+D; Primary Rate ISDN. 41 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 42 Thursday, May 4, 2000 11:59 AM bastion host BASIC RATE ISDN bastion host A computer system that ond on an asynchronous communications acts as the main connection to the Internet channel. for users of a LAN. A bastion host is usually Baud rate is often assumed to correspond to configured in such a way as to minimize the the number of bits transmitted per second, risk of intruders gaining access to the main LAN. It gets its name from the fortified pro- but baud rate and bits per second (bps) are jections on the outer walls of medieval Eu- not always the same. In high-speed digital ropean castles. communications systems, one state change can be made to represent more than one See also firewall; proxy server. data bit. batch file An ASCII file that contains See also baud; bits per second. operating system commands and other commands supported by the batch proces- Bay Networks Certified Expert A cer- sor. Batch files are used to automate repet- tification from Bay Networks, Inc., de- itive tasks. The commands in the file are signed to recognize technical expertise in executed one line at a time, just as if you constructing enterprise-wide networking had typed them at the system prompt. solutions. Currently, this certification is available in Router, Hub, and Network baud A measurement of data-transmis- Management technologies. sion speed. Originally used in measuring the speed of telegraph equipment, it now Bay Networks Certified Specialist A usually refers to the data-transmission certification from Bay Networks, Inc., de- speed of a modem or other serial device. signed to evaluate a basic level of technical See also baud rate. expertise in one or more Bay Networks product areas. Currently, this certification baud rate In communications equip- is available in Router, Hub, Network Man- ment, a measurement of the number of state agement, Remote Access, and Switching changes (from 0 to 1 or vice versa) per sec- technologies. 42 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 43 Thursday, May 4, 2000 11:59 AM Berkeley Software Distribution Unix Bay Networks, Inc. A leading manufac- See also Berkeley Software Distribution turer of networking products such as hubs, Unix; Computer Systems Research Group. routers, and switches, now venturing into the areas of network management and vir- benchmark A specific standard against tual private networks. In 1998, the compa- which some aspect of computer perfor- ny announced a merger with Northern mance can be compared. Telecom. A benchmark is a test that attempts to quantify hardware, software, or system For more information on Bay Networks, performance—usually in terms of speed, re- see www.baynetworks.com. liability, or accuracy. One of the major BBC See Baan Basic Certification. problems in determining performance is de- ciding which of the many benchmarks BBS See bulletin board system. available actually reflects the way you in- tend to use the system. bcc See blind carbon copy. See also benchmark program. BCD See binary coded decimal. benchmark program A program that beaconing In a token-ring network, the attempts to provide a consistent measure- process of informing other nodes that token ment of system performance. Here are some passing has been suspended because of a se- examples: vere error condition, such as a broken cable. I Dhrystone, which measures microproces- Communication cannot resume until the sor and memory performance condition is resolved. I Whetstone, which measures speed of BEC See Backward Error Correction. arithmetic operations I Khornerstone, which measures overall Bell communications standards A set system performance, including disk-drive of data-transmission standards developed access speed, memory access speed, and by AT&T in the 1980s that rapidly became processor performance the de facto standard for modem manufac- The Systems Performance Evaluation Co- turers. Although several of these standards operative (SPEC) developed a set of ten are still widely used in the United States, the tests to measure performance in actual ap- CCITT V series definitions are now gener- plication environments. The results of these ally accepted as the defining standards for tests are known as SPECmarks. modem use, data compression, and associ- ated hardware. BER See bit error rate; error rate. Bell Labs The research arm of AT&T Berkeley Software Distribution Unix and the birthplace of the Unix operating Abbreviated BSD Unix, and also known as system and the C programming language in Berkeley Unix. BSD Unix was developed at the 1970s. the University of California at Berkeley by 43 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 44 Thursday, May 4, 2000 11:59 AM Berkeley Unix researchers working in the Computer Sys- beta testing The process of field testing tems Research Group (CSRG) from the new hardware or software products before 1970s to 1993 when the group finally the product’s commercial or formal release. closed its doors. BSD added many signifi- Beta testing is usually done by a cross-sec- cant advanced features to Unix, including tion of users, not just programmers. The the C shell, the vi editor, TCP/IP network- purpose of beta testing is to expose the new ing additions, and virtual memory. product to as many real-life operating con- Because the CSRG was an academic group ditions as possible. producing state-of-the-art software with no If the beta tests indicate a higher-than- support obligations, BSD Unix was not sup- expected number of bugs, the developer ported in the normal way; bug fixes were usually fixes the problems and sends the sometimes made available, but it was a hit- product out again for another round of beta and-miss process at best. For this reason, testing. Preliminary versions of the product BSD Unix appealed to the research commu- documentation are also circulated for re- nity and scientific users rather than to com- view during the beta testing. mercial users who tended to use Unix from AT&T. See also alpha testing. BSD Unix 4.1 through to the last release, BGP See Border Gateway Protocol. version 4.4, and the related commercial products, including those from Sun Micro- Big Blue A nickname for International systems, DEC, and Mt Xinu, are still Business Machine Corporation (IBM), popular and in use in universities and com- which uses blue as its corporate color. mercial institutions all over the world. See also FreeBSD; Linux; NetBSD; Unix. big endian A computer architecture in which the most significant byte has the low- Berkeley Unix See Berkeley Software est address and so is stored big end first. Distribution Unix. Many processors, including those from beta site A location where beta testing is Motorola and Sun, certain RISC proces- performed before a hardware or software sors, the PDP-11, and the IBM 3270 series product is formally released for commercial are all big endian. The term comes from distribution. Jonathan Swift’s Gulliver’s Travels, in See also beta software; beta testing. which wars were fought over whether boiled eggs should be opened at the big end beta software Software that has been or the little end. released to a cross-section of typical users See also holy wars; little endian. for testing before the commercial release of the package. binaries A slang term for a group of bi- See also beta testing. nary files. 44 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 45 Thursday, May 4, 2000 11:59 AM bindery emulation binary Any scheme that uses two differ- although a certain level of configuration ent states, components, conditions, or can be done, and the user does not have the conclusions. right to modify the software in any way be- yond this simple configuration. In mathematics, the binary or base-2 num- bering system uses combinations of the See also open source software; source digits 0 and 1 to represent all values. The license. more familiar decimal system has a base of 10 (0–9). BIND 1. A Novell NetWare server utility used to bind a protocol to a network inter- Unlike computers, people find binary num- face card or device driver. bers that consist of long strings of zeros and 2. Abbreviation for Berkeley Internet ones difficult to read, so most programmers Name Domain, a BSD client/server pro- use hexadecimal (base-16) or octal (base-8) gram that manages host and IP addresses by numbers instead. matching the host name with the IP dotted Binary also refers to an executable file con- decimal address. taining a program. See also Domain Name Service; dotted binary coded decimal Abbreviated decimal. BCD. A simple system for converting deci- mal numbers into binary form, in which bindery A database maintained by older each decimal digit is converted into binary Novell NetWare network operating sys- and then stored as a single character. tems. The bindery contains information about users, servers, and other important binary file A file consisting of binary in- network configuration details in a flat da- formation. Usually, a binary file is a pro- tabase. The bindery is crucial to NetWare’s gram or data file in machine-readable form operation and is constantly consulted by rather than in human-readable ASCII text. the operating system. You can convert a binary file into a text- In NetWare 4.x and later systems, the bind- based form so that you can transmit it over ery is replaced by NetWare Directory Ser- the Internet. vices (NDS). See also base64; Multipurpose Internet See also NetWare Directory Services. Mail Extension. bindery emulation A NetWare 4.x and binary license A license granted to a later feature that allows bindery-based util- user by a software developer, entitling the ities to work with NetWare Directory Ser- user to run a specific software package un- vices (NDS) on the same network. Bindery der well-defined circumstances, using the emulation applies only to leaf objects with- binary files provided by the developer. in the Organizational container object. A binary license does not entitle the user to See also container object; leaf object; Net- a copy of the source code for the package, Ware Directory Services. 45 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 46 Thursday, May 4, 2000 11:59 AM Bindery object Bindery object A leaf object that repre- your computer supplier for information sents an object placed in the Directory tree about BIOS updates. by an upgrade utility, but that cannot be bis A term describing a secondary CCITT further identified by NetWare Directory (Consultative Committee for International Services (NDS). The Bindery object is avail- Telephony and Telegraphy) recommenda- able for the purposes of backward compat- tion that is an alternative or extension to the ibility with older, bindery-based utilities primary recommendation. For example, and applications. the CCITT V.42 standard refers to error See also leaf object; NetWare Directory correction, and the V.42 bis standard refers Services. to data compression. See also ter. bindery services See bindery emulation. B-ISDN See Broadband Integrated Ser- vices Digital Network. binding The process of establishing com- munications between the protocol device bisynchronous communications A driver and the network interface card driver. protocol used extensively in mainframe computer networks. With bisynchronous BIOS Acronym for basic input/output communications, both the sending and re- system, pronounced “bye-os.” In the PC, ceiving devices must be synchronized be- the BIOS is a set of instructions that tests the fore data transmission begins. hardware when the computer is first turned Data is collected into a package known as a on, starts to load the operating system, and frame. Each frame contains leading and lets the computer’s hardware and operating trailing characters that allow the computers system communicate with applications and to synchronize their clocks. The structure of peripheral devices, such as hard disks, a bisynchronous communications frame is printers, and video adapters. These instruc- shown in the accompanying illustration. tions are stored in ROM as a permanent The STX and ETX control characters mark part of the computer. the beginning and end of the message. BCC is a set of characters used to verify the ac- As new hardware is developed, new BIOS curacy of the transmission. routines must be created to service those de- vices. For example, BIOS support has been A more modern form of this kind of proto- added for power management and for ever- col is SDLC (Synchronous Data Link Con- larger hard disks. If you are experiencing trol), which is used in IBM’s proprietary problems accessing such devices after add- networking scheme, SNA. ing them to an existing system, your com- See also asynchronous transmission; Syn- puters BIOS may be out of date. Contact chronous Data Link Control. 46 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 47 Thursday, May 4, 2000 11:59 AM bit stuffing BISYNCHRONOUS COMMUNICATIONS bit Contraction of binary digit. A bit is Data Link Control) are both bit-oriented the basic unit of information in the binary protocols. numbering system, representing either 0 See also byte-oriented protocol. (off) or 1 (on). Bits can be grouped to form larger storage units; the most common bit rate The rate at which bits are trans- grouping is the 7- or 8-bit byte. mitted over a communications channel, de- scribed in terms of bits per second (bps). See also octet. See also baud rate. bit error rate Abbreviated BRI. The bits per inch Abbreviated bpi. The num- number of erroneous bits in a data trans- ber of bits that a tape or tape cartridge can mission or in a data transfer, such as from store per inch of length. CD-ROM to memory. bits per second Abbreviated bps. The bit-oriented protocol A communica- number of binary digits, or bits, transmitted tions protocol in which data is transmitted every second during a data-transfer proce- as a stream of bits rather than as a stream of dure. Bits per second is a measurement of bytes. the speed of operation of equipment, such as a computer’s data bus or a modem that A bit-oriented protocol uses specific se- connects a computer to a communications quences of bits as control codes, unlike a circuit. byte-oriented protocol, which uses reserved characters. HDLC (High-level Data Link bit stuffing A technique used to ensure Control) and IBMs SDLC (Synchronous that a specific bit pattern never occurs in 47 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 48 Thursday, May 4, 2000 11:59 AM blackout the data transmitted over a communica- tions across the disk. This is known as tions channel. Additional bits are added at fragmentation and, in some cases when the transmitting end and removed at the taken to an extreme, can severely limit sys- receiving end of the channel as the data is tem performance. processed. The file system’s block size is often different blackout A total loss of commercial elec- from the hard disk’s physical block size. tric power. To avoid loss of computer data See also fragmentation. due to a blackout, use a battery-backed UPS (uninterruptible power supply). block suballocation A mechanism used See also brownout; power conditioning. in Novell NetWare that allows files to share the same block space by dividing each 8K blind carbon copy Abbreviated bcc. A hard-disk block into smaller 512-byte seg- list of recipients of an e-mail message whose ments. Files needing extra space can use names do not appear in the normal message these smaller segments rather than wasting header, so the original recipient of the mes- a whole new disk block, making for more sage does not know that copies have been efficient disk-space use. forwarded to other locations. Sometimes blue screen of death Abbreviated called blind courtesy copy. BSOD. An affectionate name for the screen block In communications, a unit of trans- displayed when Microsoft Windows en- mitted information that includes header counters an error so serious that the oper- codes (such as addresses), data, and error- ating system cannot continue to run. checking codes. Windows may also display information See also checksum; error; error detection about the failure and may perform a mem- and correction. ory dump and an automatic system restart. BNC connector A small connector with blocks Sections of a tape or disk that are a half-turn locking shell for coaxial cable, read or written at the same time; units of used with thin Ethernet and RG-62 cabling. storage that are transferred as single units. The accompanying illustration shows both block size The largest contiguous male and female connectors. amount of disk space allocated by the file BNCE See Bay Networks Certified system. Files larger than the file system’s Expert. block size may be broken into smaller frag- ments when they are stored, with sections BNCS See Bay Networks Certified of the file being stored in different loca- Specialist. 48 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 49 Thursday, May 4, 2000 11:59 AM boot BNC CONNECTOR bookmark 1. In the Microsoft Win- and are sometimes described as logical dows NT Performance Monitor, a feature operators. that allows you to mark a point of interest Many popular Internet search engines al- in a log file and then return to that same low Boolean searches. point in the file at a later time. See also search engine. 2. An option available in a Web browser boot To load an operating system into that lets you mark a Web page so that you memory, usually from a hard disk, although can identify and return to a favorite site occasionally from a floppy disk. Booting is quickly and easily without having to retype generally an automatic procedure that be- the URL or even remember how you got gins when you turn on or reset your comput- there. er. A set of instructions contained in ROM begins executing. The instructions run a se- Boolean Any variable that can have a ries of power-on self tests (POSTs) to check logical value of true or false. Named after that devices such as hard disks are in work- George Boole, the developer of a branch of ing order, locate and load the operating sys- algebra based on the values of true and tem, and finally pass control over to that false, Boolean works with logical rather operating system. than numeric relationships. Boot may be derived from the expression Boolean operators include AND (logical “pulling yourself up by your own boot- conjunction), OR (logical inclusion), XOR straps” and is sometimes called bootstrap. (exclusive or), and NOT (logical negation) See also BIOS; cold boot; warm boot. 49 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 50 Thursday, May 4, 2000 11:59 AM bootable disk bootable disk Any disk capable of load- bootstrap See boot. ing and starting the operating system. Boot- Bootstrap Protocol Abbreviated able floppy disks are becoming less common BOOTP. An Internet protocol that provides because operating systems are growing larg- network configuration information to a er. In some cases, all the files needed to start diskless workstation. the operating system will not fit on even the largest-capacity floppy disk, which makes it When the workstation first boots, it sends impossible to boot from a floppy disk. out a BOOTP message on the network. This message is received by the server, which ob- BOOTCONF.SYS A Novell NetWare tains the appropriate configuration informa- configuration file that specifies how a disk- tion and returns that information to the less workstation boots the operating system workstation. This information includes the from the file server. If the file server con- workstation’s IP address, the IP address of tains several remote boot image files, the server, the host name of the server, and BOOTCONF.SYS determines which one the IP address of a default router. will be loaded onto the workstation. See also Dynamic Host Configuration See also diskless workstation. Protocol. BOOTP See Bootstrap Protocol. border A security perimeter formed by logical boundaries that can only be crossed boot ROM A type of ROM that allows a at specifically defined locations known as workstation to communicate with the net- border gateways. work file server and to read an image file See also border gateway. containing an operating system program. In this way, a workstation without a local disk border gateway A router that connects a can boot the operating system from the file private LAN to the Internet. A border gate- server. way is a security checkpoint used to force all See also diskless workstation. network traffic, either inbound or out- bound, through a single point of control. boot sector virus A virus that infects See also border; firewall; Novell Border- the master boot record of a computer by Manager; router. overwriting the original boot code with in- fected boot code. This kind of virus is usu- Border Gateway Protocol Abbreviat- ally spread to a hard disk from an infected ed BGP. A routing protocol designed to re- floppy disk being used as a boot disk. place EGP (External Gateway Protocol) and interconnect organizational networks. See also antivirus program; file-infecting BGP, unlike EGP, evaluates each of the pos- virus; macro virus; multipart virus; poly- sible routes for the best one. morphic virus; stealth virus; Trojan Horse; vaccine; virus. Border router See Area Border router. 50 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 51 Thursday, May 4, 2000 11:59 AM bridge Borland International, Inc. See Inprise essential. The implication is that the design- Corporation. er should have known better than to leave those features out of the product. bot See robot. breach A loss of network security as a re- bounce The return of an e-mail message sult of a successful attack. to its original sender due to an error in de- livery. You may have made a simple spelling See also brute-force attack; dictionary at- mistake in the e-mail address, the recipient’s tack; social engineering. computer system may be down, or the recip- breakout box A small device that can be ient may no longer subscribe to or have an connected into a multicore cable for testing account on the system. A returned e-mail the signals in a transmission. Small LEDs in message will usually contain a description of the breakout box indicate when a signal is why the message bounced. transmitted over one of the lines. Switches Bourne shell In Unix, a popular com- or short jumper cables can be used to re- mand interpreter with a built-in program- route these signals to other pins as required ming language. for troubleshooting. The Bourne shell, developed by Dr. Steven See also sniffer. Bourne of Bell Labs, is the oldest Unix shell still in popular use and features a built-in BRI See Basic Rate ISDN. command set for writing shell scripts, bridge A hardware device used to con- background execution of commands, in- nect LANs so that they can exchange data. put and output redirection, job control, Bridges can work with networks that use and a set of shell variables to allow envi- different wiring or network protocols, join- ronment customization. ing two or more LAN segments to form See also Bash; C shell; Korn shell; Linux; what appears to be a single network. Unix shell. A bridge operates at the data-link layer of bpi See bits per inch. the OSI Reference Model for computer-to- computer communications. It manages the bps See bits per second. flow of traffic between the two LANs by brain damaged An expression used to reading the address of every packet of data describe any poorly designed program or that it receives. piece of hardware that does not include See also brouter; gateway; OSI Reference those features most users would consider Model; router. 51 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 52 Thursday, May 4, 2000 11:59 AM BrightWorks BRIDGE BrightWorks A package of network that handles high-bandwidth applications, management utilities from McAfee Associ- such as video, voice, data, and graphics. ates that includes hardware and software SMDS (Switched Multimegabit Data Ser- inventory, application metering, remote vices) and ATM (Asynchronous Transfer control of clients, virus detection, and a Mode) are two BISDN services that can help-desk utility. provide a huge bandwidth. Broadband Integrated Services Digital See also Asynchronous Transfer Mode; Network Abbreviated B-ISDN. A high- SONET; Switched Multimegabit Data speed communications standard for WANs Services. BROADBAND INTEGRATED SERVICES DIGITAL NETWORK broadband network A technique for channel. Sometimes called wideband trans- transmitting a large amount of information, mission, it is based on the same technology including voice, data, and video, over long used by cable television. distances using the same communications 52 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 53 Thursday, May 4, 2000 11:59 AM brouter The transmission capacity is divided into tected from each other by guard channels of several distinct channels that can be used unused frequencies. A broadband network concurrently by different networks, nor- can operate at speeds of up to 20Mbps. mally by frequency-division multiplexing See also baseband network; multiplexer. (FDM). The individual channels are pro- BROADBAND NETWORK broadcast To send a message to all users broker A Novell Distributed Print Servic- currently logged in to the network. es (NDPS) service providing management services for network printers, including See also multicast. event notification and storage of printer re- sources such as device drivers. broadcast storm Congestion on a net- work that occurs when a large number of brouter A networking device that com- frames are transmitted by many worksta- bines the attributes of a bridge and a router. tions in response to a transmission from one A brouter can route one or more specific workstation. protocols, such as TCP/IP, and bridge all 53 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 54 Thursday, May 4, 2000 11:59 AM brownout others, for example, and can operate at ei- See also denial of service attack; dictionary ther the data-link layer or the network layer attack; social engineering; Trojan Horse. of the OSI Reference Model. BSD Unix See Berkeley Software Distri- See also gateway. bution Unix. brownout A short period of low volt- BSOD See blue screen of death. age, often the result of an unusually heavy buffer An area of memory set aside for demand for power, that may cause your temporary storage of data. Often, the data computer to crash. If your area experienc- remains in the buffer until some external es frequent brownouts, consider using a event finishes. A buffer can compensate for UPS (uninterruptible power supply) as a the differences in transmission or process- battery backup system. ing speed between two devices or between a browse list A list of computers and ser- computer and a peripheral device, such as a vices available on a network. printer. Buffers are implemented in a variety of ways, browser 1. An application program used including first-in-first-out (FIFO) used for to explore Internet resources. A browser lets pipes and last-in-last-out used for stacks and you wander from Web site to Web site with- circular buffers such as event logs. out concern for the technical details of the See also pipe. links between them or the specific methods used to access them and presents the infor- buffered repeater Any device that am- mation—text, graphics, sound, or video—as plifies and retransmits a signal so that it can a document on the screen. travel greater distances. A buffered repeater 2. A small application used to scan a data- can also control the flow of information to base or a list of files. prevent collisions. See also repeater. 3. In Windows NT networking, a mecha- nism used as a name service. bug A logical or programming error in See also Web browser; World Wide Web. hardware or software that causes a mal- function of some sort. If the problem is in brute-force attack A technique em- software, it can be fixed by changes to the ployed by intruders that checks every pass- program. If the fault is in hardware, new word in a password file against every circuits must be designed and constructed. possible password generated sequentially. Some bugs are fatal and may cause a pro- A brute-force attack is very clumsy, is usu- gram to stop responding or cause data loss, ally considered the last resort in an attack, others are just annoying, and many are not takes a long time to run, and is easily de- even noticeable. The term apparently orig- tected by even the most modest security pre- inates from the days of the first electrome- cautions. Also called a keyspace attack. chanical computers, when a problem was 54 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 55 Thursday, May 4, 2000 11:59 AM bus mastering traced to a moth caught between two con- of the interface card, which ensures that ev- tacts inside the machinery. ery card has a unique address. See also bug fix. See also hardware address. bug fix A release of hardware or soft- burst mode A method of data transmis- ware that corrects known bugs but does not sion in which information is collected and contain new features. Such releases are usu- then sent in one single high-speed transmis- ally designated by an increase in the decimal sion, rather than one packet or character at portion of the revision number; for exam- a time. ple, the revision level may advance from 2.0 Systems that use multiplexers to serve sever- to 2.01 or 2.1, rather than from 2.0 to 3.0. al channels often use burst mode to service each channel in turn. Much LAN traffic can built-in groups The default groups pro- be considered burst mode transmission: long vided with some operating systems that de- periods of inactivity punctuated by short fine a collection of rights and permissions bursts of intense activity. In Novell Net- for members. Using built-in groups is an Ware, burst mode is known as packet burst. easy way of providing access to commonly used network resources. bus An electronic pathway along which signals are sent from one part of a computer bulletin board system Abbreviated to another. A PC contains several buses, BBS. A computer system equipped with one each used for a different purpose: or more modems, serving as a message- passing system or centralized information I The address bus allocates memory source, usually for a particular special in- addresses. terest group. Bulletin board systems were I The data bus carries data between the pro- often established by software vendors and cessor and memory. by PC user groups in the past, but have been replaced in recent times by Web sites. I The control bus carries signals from the control unit. bundled software Programs combined See also architecture; Extended Industry into a single package sold for a single price. Standard Architecture; Industry Standard Sales aimed at a specific target, such as the Architecture; local bus; Microchannel medical profession, usually bundle hard- Architecture; Peripheral Component ware with application-specific software Interconnect local bus. suited to that profession. See also unbundled software. bus mastering A technique that allows certain advanced bus architectures to dele- burned-in address The hardware ad- gate control of data transfers between the dress on a network interface card (NIC). CPU and associated peripheral devices to an This address is assigned by the manufacturer add-in board. This technique gives network 55 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 56 Thursday, May 4, 2000 11:59 AM bus network interface cards (NICs) greater system bus Peripheral Component Interconnect local access and higher data-transfer speeds. bus. In the PC, bus mastering is supported by all bus network In networking, a topology the common architectures except for the that allows all network nodes to receive the older Industry Standard Architecture. same message through the network cable at See also Extended Industry Standard Ar- the same time. chitecture; Industry Standard Architecture; See also ring network; star network; token- local bus; MicroChannel Architecture; ring network. BUS NETWORK byte Contraction of binary digit eight. A bytecode An intermediate form of com- group of bits. In computer storage terms, a puter code produced by Java and other pro- byte usually holds a single character, such gramming languages. as a number, letter, or symbol. A byte usu- Most language compilers create code that ally contains 8 bits, but on some older sys- is ready to run on a specific kind of pro- tems, a byte may only have 7 bits or may cessor. Java creates the bytecode in an ab- have as many as 11. stract, processor-independent form, which Because bytes represent a very small requires further processing before it can amount of storage, they are usually actually execute on a computer. When a byte-code file is downloaded into your grouped into kilobytes (1,024 bytes), computer from a Web page, it provides 70 megabytes (1,048,576 bytes), and gi- to 80 percent of the data needed to run the gabytes (1,073,741,824 bytes) for conve- Java applet; the other 20 to 30 percent is nience when describing hard-disk capacity provided by the Java run-time environ- or computer memory size. ment, which tells the applet how to per- See also octet. form on the target computer system. 56 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 57 Thursday, May 4, 2000 11:59 AM byte-oriented protocol See also Java; Java applet; just-in-time formation, the protocol uses control char- compiler; sandbox. acters that have a special meaning for the transmitting and receiving stations. Most of byte-oriented protocol A communica- the common asynchronous communica- tions protocol in which data is transmitted tions protocols used in conjunction with as a series of bytes, or characters. In order modems are byte-oriented protocols. to distinguish the data from the control in- See also bit-oriented protocol. 57 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 58 Thursday, May 4, 2000 11:59 AM C2 C C2 One of a series of seven levels of com- management solutions, Cabletron is also puter security defined by the National Se- moving into Gigabit Ethernet and data, curity Agency. voice, and video systems. C2-level security requires that users are For more information about Cabletron, see logged in and tracked during their session, www.cabletron.com. that all resources have owners, that objects cabling standards National cabling such as files be protected from processes standards, concerned with the performance that might damage them, that events can be of cables and connectors under conditions audited, and that the system has adequate of actual use, are specified by the National protection against intrusion. Electric Code, American National Stan- C2 security applies to a stand-alone system, dards Institute, and Underwriters Labora- so in theory a networked computer cannot tories. Other standards have been specified be C2-compliant; following the guidelines by the Electronics Industry Association/ can certainly help you to set up a more se- Telecommunications Industries Associa- cure system. tion (EIA/TIA). Standards include: CA See certificate authority. I ANSI/EIA/TIA-568-1991 Commercial Building Telecommunications Wiring. cable modem A modem that sends and I EIA/TIA TSB-36 Additional Cable Speci- receives signals through a coaxial cable fications for UTP Cables. 1991. connected to a cable-television system, rather than through conventional tele- I EIA/TIA TSB-40 Telecommunications phone lines. Systems Bulletin—Additional Transmis- sion Specifications for UTP Connecting Cable modems, with speeds of up to Hardware. 1992. 500Kbps, are faster than current conven- tional modems, but are subject to perfor- I ANSI/EIA/TIA-568A 1995 revises the mance changes as system load increases. original 568 document and adds material Theoretical data rates are much higher than from TSB-36 and TSB-40. those achieved with conventional modems; I ANSI/EIA/TIA-569-1990 Commercial downstream rates of up to 36Mbps are pos- Building Standard for Telecommunica- sible, with 3Mbps to 10Mbps likely, and tions Pathways and Spaces. upstream rates up to 10Mbps. I ANSI/EIA/TIA-570-1991 Residential and Cabletron Systems A leading producer Light Commercial Telecommunications of Internet and intranet hardware and Wiring Standard. 58 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 59 Thursday, May 4, 2000 11:59 AM cache buffer I ANSI/EIA/TIA-606-1993 Administration There are several types of caches: Standard for the Telecommunications In- I Direct-mapped cache A location in the frastructure of Commercial Buildings. cache corresponds to several specific loca- I ANSI/EIA/TIA-607-1994 Commercial tions in memory, so when the processor Building Grounding and Bonding Re- calls for certain data, the cache can locate quirements for Telecommunications. it quickly. However, since several blocks Local codes and standards may impose ad- in RAM correspond to that same location ditional requirements. in the cache, the cache may spend its time refreshing itself and calling main memory. Underwriters Laboratories (UL) tests cable I Fully associative cache Information and other devices to determine the condi- from RAM may be placed in any free tions under which the device will function blocks in the cache so that the most re- safely. Two important tests for cable per- cently accessed data is usually present; formance are: however, the search to find that informa- I UL-910, which tests smoke emission and tion may be slow because the cache has to flame spread for plenum cable index the data in order to find it. I UL-1666, which tests smoke emission and I Set-associative cache Information from flame spread for riser cable RAM is kept in sets, and these sets may CAC See Connection Admission have multiple locations, each holding a Control. block of data; each block may be in any of the sets, but it will only be in one location cache Pronounced “cash.” A special area within that set. Search time is shortened, of memory, managed by a cache controller, and frequently used data are less likely to that improves performance by storing the be overwritten. A set-associative cache contents of frequently accessed memory lo- may use two, four, or eight sets. cations and their addresses. See also disk cache; wait state; write-back A memory cache and a disk cache are not cache; write-through cache. the same. A memory cache is implemented in hardware and speeds up access to mem- cache buffer A Novell NetWare imple- ory. A disk cache is software that improves mentation of a disk cache used to speed hard-disk performance. server disk accesses, thereby allowing workstations to access data more quickly. When the processor references a memory Reading data from cache memory is much address, the cache checks to see if it holds faster than reading data from the hard disk. that address. If it does, the information is passed directly to the processor, so RAM NetWare uses cache buffers for a variety of access is not necessary. A cache can speed purposes: up operations in a computer whose RAM I For use by NetWare Loadable Modules access is slow compared with its processor (NLMs), such as LAN drivers, database speed, because cache memory is always servers, communications servers, and faster than normal RAM. print servers 59 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 60 Thursday, May 4, 2000 11:59 AM cache buffer pool I To cache each volume’s FAT disk drives. Most current CD-ROM drives do not require a caddy. I To cache files currently in use I To build a hash table of directory CAE See Common Application information Environment. See also disk cache. CAI See Computer Associates International. cache buffer pool In Novell NetWare, Caldera, Inc. A software company in the amount of memory available for use af- Provo, Utah, that repackages one of the ter the SERVER.EXE file has been loaded most popular versions of Linux under the into memory. Memory in the pool can be name of OpenLinux. used for a variety of purposes, including caching the file allocation tables for each For more information on Caldera, see volume and creating a hash table of direc- www.caldera.com. tory information. callback modem Also known as a dial- See also hash table. back modem. A special modem that does not answer an incoming call, but instead re- cache controller Pronounced “cash quires the caller to enter a code and hang up controller.” A special-purpose processor so that the modem can return the call. As whose sole task is to manage cache memo- long as the entered code matches a previ- ry. On newer processors, such as the Intel ously authorized number, the modem dials Pentium II, cache management is integrated the number. Callback modems are useful in directly into the processor. installations for which communications lines must be available for remote users but See also cache. data must be protected from intruders. cache memory Pronounced “cash caller ID See automatic number memory.” A relatively small section of very identification. fast memory (often static RAM) reserved for the temporary storage of the data or in- call packet A block of data that carries structions likely to be needed next by the addressing information, as well as any oth- processor. er information needed to establish an X.25 switched virtual circuit. Cache memory integrated directly onto the microprocessor is called primary cache or campus network A network that con- L1 cache, and cache memory located in an nects LANs from multiple departments in- external circuit is known as secondary side a single building or set of buildings. cache or L2 cache. Campus networks are LANs because they do not include WAN services, even though See also cache. they may extend for several miles. caddy The flat plastic container used to canonical The usual standard Unix way load a compact disc into certain CD-ROM of doing something. This term has a more 60 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 61 Thursday, May 4, 2000 11:59 AM carrier signal precise meaning in mathematics, in which display cursor to return to the first position rules dictate the way that formulas are writ- of the current line. ten, but in Unix, it tends to mean “accord- See also line feed. ing to ancient or religious law.” See also holy wars. carrier An analog signal of fixed ampli- tude and frequency that is combined with a Canon, Inc. One of the world’s leading data-carrying signal to produce an output suppliers of imaging products, electronic signal suitable for transmitting data. equipment, computer printers, fax ma- See also carrier signal. chines, and scanners. For more information on Canon, see carrier detect Abbreviated CD. An elec- www.canon.com. trical signal sent from a modem to the at- tached computer to indicate that the modem CAPI See Cryptography API. is online. card A printed circuit board or adapter See also Data Carrier Detect; RS-232-C. that you plug into a computer to add sup- port for a specific piece of hardware. Carrier Sense Multiple Access/ Collision Detection Abbreviated See also expansion board; expansion bus. CSMA/CD. A baseband protocol with a built-in collision-detection technique. Each card services Part of the software sup- node on the network listens first and trans- port needed for PCMCIA hardware devices mits only when the line is free. If two nodes in a portable computer. Card services con- transmit at exactly the same time and a col- trol the use of system interrupts, memory, lision occurs, both nodes stop transmitting. and power management. Then, to avoid a subsequent collision, each When an application wants to access a PC- node waits for a different random length of MCIA card, it always goes through the card time before attempting to transmit again. services software and never communicates Ethernet and 802.3 LANs use CSMA/CD directly with the underlying hardware. For access methods. example, if you use a PCMCIA modem, it is See also collision; demand priority; Fast the card services, not the applications pro- Ethernet; token passing. gram, that establishes which communica- tions port and which interrupts and I/O carrier signal A signal of chosen fre- addresses are in use. quency generated to carry data; often used See also device driver; PC Memory Card for long-distance transmissions. A carrier International Association; socket services. signal does not convey any information until the data is added to the signal by carriage return A control character modulation and then decoded on the re- (ASCII 13) that signals the print head or ceiving end by demodulation. 61 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 62 Thursday, May 4, 2000 11:59 AM cascaded star cascaded star A network topology in nected in a succession of levels, which permits which multiple hubs or data centers are con- many more connections than a single level. CASCADED STAR cascading menus In Microsoft Win- For more information on Castanet, see dows 2000, a function that presents the www.marimba.com. contents of network drives or special fold- See also server push. ers such as Control Panel as menu items that can be selected by name. Category 1–5 The Electronics Industry See also personalized menus. Association/Telecommunications Industry Association (EIA/TIA) 586 cabling stan- Castanet A collection of software-update dards, sometimes abbreviated CAT 1-5, as tools from Marimba, Inc. that operate over follows: the Internet. Based on Java technology, Cas- I Category 1 For unshielded twisted-pair tanet can automatically deliver software up- (UTP) telephone cable. This cable may be dates not only for Java programs, but also used for voice, but is not suitable for data for those written in C, C++, and Visual transmissions. Basic, and because only the updated content is downloaded, performance is optimized. 62 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 63 Thursday, May 4, 2000 11:59 AM CCITT V Series I Category 2 For UTP cable use at speeds CCITT See Consultative Committee for up to 4Mbps. Category 2 cable is similar International Telephony and Telegraphy. to IBM Cabling System Type 3 cable. CCITT Groups 1–4 A set of four stan- I Category 3 For UTP cable use at speeds dards for facsimile transmissions. Groups 1 up to 10Mbps. Category 3 cable is the and 2, which are no longer used, define an- minimum requirement for 10BaseT and is alog facsimile transmissions. Groups 3 and required for Token Ring. This cable has 4 describe digital systems, as follows: four pairs of conductors and three twists per foot. I CCITT Group 3 Specifies a 9600bps I Category 4 For the lowest acceptable modem to transmit standard images of grade of UTP cable for use with 16Mbps 203 dpi horizontally by 98 dpi vertically Token Ring. in standard mode, and 203 dpi by 198 dpi I Category 5 For 100-ohm, four-wire in fine mode. twisted-pair copper cable for use at speeds I CCITT Group 4 Supports images up to up to 100Mbps with Ethernet or ATM 400 dpi for high-speed transmission over (Asynchronous Transfer Mode). This ca- a digital data network (for example, IS- ble is low-capacitance and shows low DN), rather than over a dial-up telephone crosstalk when installed according to line. specifications. I CCITT is now known as the International See also cabling standards; Type 1–9 Telecommunication Union. cable. See also International Telecommunication CAU See Controlled Access Unit. Union. CAV See constant angular velocity. CCITT V Series A set of recommended CBCP See Certified Business Continuity standards for data communications, in- Professional. cluding transmission speeds and operation- al modes, issued by CCITT, now known as CBE See Certified Banyan Engineer. the International Telecommunication CBR See Constant Bit Rate. Union. CBS See Certified Banyan Specialist. Each standard is assigned a number, al- though not in chronological order. Higher CCDA See Cisco Certified Design numbers do not always indicate a newer Associate. standard. A second or revised version is CCDP See Cisco Certified Design indicated by bis, and ter indicates a third Professional. version. CCIE See Cisco Certified Internetwork- See also International Telecommunication ing Expert. Union. 63 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 64 Thursday, May 4, 2000 11:59 AM CCITT X Series CCITT X Series A set of recommended CD-Recordable Abbreviated CD-R. Us- standards issued by CCITT to standardize ing CD-R, you can write to the disc only protocols and equipment used in public and once; after that, the disc can only be read private computer networks. The standards from and not written to. include transmission speeds, interfaces to From a functional point of view, a CD-R and between networks, and operation of and a CD-ROM are identical; you can read user hardware. CCITT is now known as the CD-R discs using almost any CD-ROM International Telecommunication Union. drive, although the processes that create the See also International Telecommunication discs are slightly different. Low-cost CD-R Union. drives are available from several manu- facturers, including Kao, Kodak, Mitsui, CCNA See Cisco Certified Network Phillips, Ricoh, Sony, TDK, 3M, and Associate. Verbatim. CCNP See Cisco Certified Network See also CD ReWritable; digital video disc; Professional. Magneto-optical storage; WORM. CCP See Certified Computing CD ReWritable Abbreviated CD-RW. A Professional. CD format that can be written to and erased CCP See Compression Control Protocol. as many as 1000 times. CD See carrier detect. From a functional point of view, a CD-RW and a CD-ROM are identical, but not all CDA See Certified Database CD-ROM drives can read CD-RW discs. Administrator. Low-cost CD-RW drives are available from several manufacturers, including Kodak, CDDI See Copper Distributed Data Mitsui, Phillips, and Sony. Interface. See also CD-Recordable; digital video disc; CDE See Common Desktop Magneto-optical storage; WORM. Environment. CD-I See Compact Disc-Interactive. CD-ROM See Compact Disc—Read- Only Memory. CDIA See Certified Document Imaging Architect. CD-ROM disk drive A disk device that uses compact disc technology for informa- CDMA See Code Division Multiple tion storage. Many CD-ROM disk drives Access. also have headphone jacks, external speak- CDP See Cisco Discovery Protocol. er jacks, and a volume control. CD-ROM disk drives designed for com- CDPD See Cellular Digital Packet Data. puter use are more expensive than audio CD-R See CD-Recordable. CD players, because CD-ROM disk drives 64 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 65 Thursday, May 4, 2000 11:59 AM central processing unit are manufactured to much higher toler- Cell Loss Priority Abbreviated CLP. In ances. If a CD player misreads a small an Asynchronous Transfer Mode (ATM) amount of data, the human ear probably cell, a field contained in the 5-byte cell will not detect the difference; if a CD- header that defines how to drop a cell if net- ROM disk drive misreads a few bytes of a work congestion occurs. The value holds program, the program will not run. priority values, with 0 indicating a cell with the highest priority. The two most popular CD-ROM drive in- terface cards are SCSI and ATAPI (AT At- See also Header Error Control; Payload tachment Packet Interface). ATAPI is part of Type Identifier; Virtual Channel Identifier; the Enhanced IDE specification introduced Virtual Path Identifier. by Western Digital in 1994 and lets you plug cell relay A form of packet transmission an IDE CD-ROM directly into an IDE con- used in Broadcast Integrated Services Dig- troller on the system’s motherboard. Other ital Network (B-ISDN) networks that uses CD-ROM drives may use the computer’s a fixed-length, 53-byte cell over a packet- parallel port or a PCMCIA connection. switched network. Also known as Asyn- See also Compact Disc—Read-Only chronous Transfer Mode (ATM). Memory. cell switching A term that describes how a cellular telephone system switches CD-ROM Extended Architecture Ab- from one cell to the next as the signal breviated CD-ROM/XA. An extension to strength fades. The switch takes about 300 the CD-ROM format, developed by Mi- milliseconds to complete and is not notice- crosoft, Phillips, and Sony, that allows for able by the user. the storage of audio and visual information on compact disc so that you can play the au- Cellular Digital Packet Data Abbrevi- dio at the same time you view the visual data. ated CDPD. A method used in cellular com- munications and wireless modems for CD-ROM/XA is compatible with the High sending data more efficiently by using any Sierra specification, also known as ISO idle cellular channel. Capacity becomes standard 9660. available for data transmissions when a CD-ROM/XA See CD-ROM Extended voice call is terminated or when a call is Architecture. switched from cell to cell. CDPD uses voice channels, but can switch CD-RW See CD ReWritable. to a new frequency if a voice transmission begins in the cell currently in use. cell Any fixed-length data packet. For example, Asynchronous Transfer Mode central processing unit Abbreviated (ATM) uses 53-byte cells, consisting of CPU. The computing and control part of the 48 bytes of data and 5 bytes of header computer. The CPU in a mainframe comput- information. er may be contained on many printed circuit 65 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 66 Thursday, May 4, 2000 11:59 AM Centrex boards. In a minicomputer, the CPU may be issues certificates; often called a “trusted contained on several boards. The CPU in a authority.” PC is usually contained in a single, extremely powerful microprocessor. Certified Application Developer for Developer/2000 A certification from Centrex Acronym formed from Central Oracle consisting of a set of exams covering Exchange. Services provided to a company Structured Query Language, the creation of by the local telephone company. All the procedures using Oracle Procedure Builder, switching takes place at the telephone com- using Developer/2000, and managing the pany’s central office rather than at the cus- user interface. tomer site, so Centrex services are easy to expand. Certified Banyan Engineer Abbreviat- ed CBE. A premium certification from Centronics parallel interface A stan- Banyan designed to evaluate technical dard 36-pin interface used to connect a PC to knowledge of the Banyan VINES network a peripheral device, such as a printer; origi- operating system. A candidate must com- nally developed by the printer manufacturer plete two required courses and pass two Centronics, Inc. The standard defines eight exams. parallel data lines, plus additional lines for status and control information. Certified Banyan Specialist Abbrevi- See also parallel port. ated CBS. A basic certification from Banyan designed to evaluate technical knowledge CERN See Conseil Européen pour la of the Banyan VINES network operating Researche Nucléaire. system. A candidate must complete one re- quired course and pass three exams. An ad- CERT See Computer Emergency ditional certification concentrates on the Response Team. integration of Banyan’s StreetTalk onto certificate An encrypted digital signa- Microsoft Windows 2000 servers; to com- ture used for authentication to prove that plete this certification, you must first be- you are who you claim to be, either as an in- come a Microsoft Certified Professional. dividual, the provider of a service, the ven- dor of a product, or a corporation, or to Certified Business Continuity guarantee that an e-mail message is actually Professional Abbreviated CBCP. A certi- from the person you think it is from and fication from Disaster Recovery Institute In- that it has not been altered in any way dur- ternational (DRII) that covers intermediate ing transmission. information on business continuity planning and disaster recovery and associated work See also authentication; certificate author- experience and board certification. ity; Secure Sockets Layer. See also Associate Business Continuity certificate authority Abbreviated CA. Professional; Master Business Continu- A trusted organization that validates and ity Professional. 66 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 67 Thursday, May 4, 2000 11:59 AM Certified Lotus Specialist Certified Computing Professional Consortium (ISC)2 designed for system secu- Abbreviated CCP. A certification from the rity experts with at least three years of prac- Institute for Certification of Computing tical experience. The exam covers access Professionals designed for experienced pro- control systems, operations security, cryp- fessionals with more than four years expe- tography, applications and systems plan- rience in a wide variety of computing and ning, business continuity and disaster related tasks. planning, telecommunications and network security, ethics, and the law. Certified Database Administrator 1. Abbreviated CDA. A certification from Certified Java Developer Abbreviated Oracle that covers knowledge of Structured CJD. An advanced certification from Sun Query Language, administration of Oracle Microsystems designed to evaluate Java products, along with backup and recovery, programming language skills. and system performance tuning. See also Certified Java Programmer. 2. Abbreviated CDA. A certification from Sybase that covers designing, building, and Certified Java Programmer Abbrevi- supporting Sybase SQL Server databases. ated CJP. A certification from Sun Microsystems designed to evaluate Java See also Certified Performance and Tun- programming language skills. ing Specialist. See also Certified Java Developer. Certified Document Imaging Architect Abbreviated CDIA. A certification from the Certified Lotus Professional Abbrevi- Computer Technology Industry Association ated CLP. A certification from Lotus de- (CompTIA) that assesses skills in document signed to evaluate a wide range of skills and management, including scanning and stor- knowledge of Lotus products. Several certifi- ing documents in digital form and using op- cations are available, including CLP: Applica- tical character recognition software. tion Developer, CLP: Principal Application Developer, CLP: System Administrator, CLP: Certified Information System Auditor Principal System Administrator, CLP: Abbreviated CISA. A certification from the cc:Mail System Administrator. Information Systems Audit and Control As- See also Certified Lotus Specialist. sociation (ISACA) that covers ethics, secu- rity, system organization and management, Certified Lotus Specialist Abbreviated and system development, acquisition, and CLS. A certification from Lotus designed to maintenance. evaluate knowledge of a single Lotus prod- uct. Options include certification in Lotus Certified Information Systems Secu- Domino, Lotus 1-2-3, Lotus Notes, and rity Professional Abbreviated CISSP. cc:Mail. A certification from the International In- formation System Security Certification See also Certified Lotus Professional. 67 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 68 Thursday, May 4, 2000 11:59 AM Certified Network Professional Certified Network Professional Ab- well as admission to network-related events breviated CNP. A certification from the and complementary subscriptions. Network Professional Association (NPA) See also Certified Novell Engineer. that involves meeting requirements in the areas of client operating systems, network- Certified Novell Instructor Abbreviat- ing hardware, network operating systems, ed CNI. A Novell certification program for communications protocols, and network trainers who want to teach Novell courses. topologies. Two years of relevant work ex- Once certified, by passing the appropriate perience and two vendor-based certifica- exam at the instructor level, a CNI can tions are required to complete the program. teach any instructor-led Novell course, in- cluding those for Certified Novell Admin- Certified Novell Administrator Abbre- istrator (CNA), Certified Novell Engineer viated CNA. A Novell certification program (CNE), and Master CNE (MCNE). for network administrators responsible for See also Master Certified Novell Instructor. the day-to-day operation of a network. Within the CNA program, a candidate can Certified Performance and Tuning specialize in one or more Novell products, Specialist Abbreviated CPTS. A certifi- including IntranetWare, NetWare, or cation from Sybase that tests for proficiency GroupWise. across a wide range of database administra- See also Certified Novell Engineer; Master tion, tuning, and performance concepts. Certified Novell Engineer. See also Certified Database Administrator. Certified Novell Engineer Abbreviated Certified PowerBuilder Developer CNE. A Novell certification program for Associate Abbreviated CPDA. A certifi- cation from Sybase designed for experi- technical professionals concerned with net- enced PowerBuilder developers that tests work system design, implementation, and knowledge in the areas of client/server ar- maintenance. Within the CNE program, a chitecture, object-oriented programming, candidate can specialize in one or more No- relational databases, and Structured Query vell products, including IntranetWare, Net- Language. Ware, or GroupWise. See also Certified PowerBuilder Developer See also Certified Novell Administrator; Professional. Master Certified Novell Engineer. Certified PowerBuilder Developer Certified Novell Engineer Professional Professional Abbreviated CPDP. A certi- Association Abbreviated CNEPA. An fication from Sybase designed for experi- association of Certified Novell Engineers enced PowerBuilder developers that requires (CNEs) that provides benefits, such as hands-on experience building PowerBuilder workshops demonstrating how to config- applications as well as a demonstration of ure and troubleshoot Novell products, as good development practices. 68 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 69 Thursday, May 4, 2000 11:59 AM character See also Certified PowerBuilder Developer channel may refer to a physical medium (for Associate. example, a coaxial cable) or to a specific frequency within a larger channel. Certified Solutions Expert Abbreviat- 2. In Internet Relay Chat (IRC), a named ed CSE. A pair of Internet certifications forum where you can chat in real time with from IBM. CSE: Net.Commerce is aimed other users; also known as a chat room. at the developers of Internet store fronts and other financial transactions over the channelization The process of dividing Internet. CSE: Firewall is a security-related the bandwidth of a communications circuit certification. into smaller increments. See also T1. Certified Unicenter Engineer Abbrevi- ated CUE. A certification from Computer channelized T1 See T1. Associates designed to evaluate expertise in the Unicenter TNG product line. Channel Service Unit Abbreviated CSU. A device that functions as a certified CGI See Common Gateway Interface. safe electrical circuit, acting as a buffer Challenge-Handshake Authentication between the customer’s equipment and a Protocol Abbreviated CHAP. A method public carrier’s WAN. of authentication that you can use when A CSU prevents faulty CPE (customer-pre- connecting to an ISP that allows you to log mises equipment), such as DSUs (data ser- on automatically. vice units), from affecting a public carrier’s See also Password Authentication transmission systems and ensures that all Protocol. signals placed on the line are appropriately timed and formed. All CSU designs must be challenge-response authentication A approved and certified by the FCC. method of authentication used by Microsoft See also Data Service Unit. Windows 2000 and other operating systems. CHAP See Challenge-Handshake When a user contacts a server, the server re- Authentication Protocol. sponds with a challenge, upon which the user then performs a cryptographic opera- character A symbol that corresponds to a tion and returns the result to the server. The key on the keyboard. A character can be a let- server then performs the same operation, ter, a number, punctuation, or a special sym- and if the two results are the same, the user bol and is usually stored as a single byte. A is considered authentic. collection of related characters is known as a See also clear text authentication. character set, and the most common charac- ter set on PC systems is the American Stan- channel 1. In communications, any con- dard Code for Information Interchange necting path that carries information from (ASCII). Some larger IBM systems still use a sending device to a receiving device. A Extended Binary Coded Decimal Interchange 69 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 70 Thursday, May 4, 2000 11:59 AM character-based interface Code (EBCDIC). In an attempt to rationalize characters per second Abbreviated the many international character sets in use cps. The number of characters, or bytes, these days, some systems use more than one transmitted every second during a data byte to store a character. transfer. A measurement of the speed of op- eration of equipment, such as serial printers See also American Standard Code for and terminals. Information Interchange; Extended Bi- nary Coded Decimal Interchange Code; character string Any group of alphanu- Unicode. meric characters treated as a single unit. Also known as a string. character-based interface An operat- ing system or application that uses text cheapernet wire See thin Ethernet. characters rather than graphical techniques for the user interface. checkpointing The process of moving transactions from the transaction log to See also command line; graphical user their permanent disk location. interface. checksum A method of providing infor- character code A code that represents mation for error detection, usually calculat- one specific alphanumeric or control char- ed by summing a set of values. acter in a set of characters. The checksum is usually appended to the See also American Standard Code for end of the data that it is calculated from so Information Interchange; Extended that they can be compared. For example, Binary Coded Decimal Interchange Code; Xmodem, a popular file-transfer protocol, Unicode. uses a 1-byte checksum calculated by add- ing all the ASCII values for all 128 data character mode A mode in which the bytes and ignoring any numeric overflow. computer displays characters on the screen The checksum is added to the end of the using the built-in character set, but does not Xmodem data packet. This type of check- show any graphics characters or a mouse sum does not always detect all errors. In lat- pointer. Also known as text mode. er versions of the Xmodem protocol, cyclical redundancy check (CRC) is used in- character set A standard group of let- stead for more rigorous error control. ters, numbers, punctuation marks, special See also cyclical redundancy check; error symbols, and control characters used by a detection and correction. computer. See also American Standard Code for child domain In Microsoft Windows Information Interchange; Extended 2000 Server, a secondary domain beneath Binary Coded Decimal Interchange Code; the top-level domain in a Windows 2000 Unicode. domain tree. 70 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 71 Thursday, May 4, 2000 11:59 AM Cisco Certified Internetworking Expert See also first-layer domain; parent do- Cirrus Logic, Inc. A leading manufac- main; root domain. turer of integrated circuits, particularly semiconductor wafers, Cirrus Logic has chip A slang expression for integrated also moved into the areas of 56K modem circuit. chip sets and sound-card chip sets. See also integrated circuit. For more information on Cirrus Logic, see www.cirrus.com. choke packet A packet used for flow control. A node that notices congestion on CIS See CompuServe. the network generates a choke packet and sends it toward the source of the conges- CISA See Certified Information System tion, which is then required to reduce its Auditor. sending rate. CISC See complex instruction set CHRP See Common Hardware Refer- computing. ence Platform. ciscoBus The bus used in routers from CICS See Customer Information Con- Cisco Systems, Inc. trol System. See also Cisco Extended Bus; switch CIDR See Classless Inter-Domain processor. Routing. ciscoBus controller See switch CIFS See Common Internet File System. processor. CIOS See Internetworking Operating Cisco Certified Design Associate Ab- System. breviated CCDA. A certification from Cisco designed to evaluate knowledge of relatively circuit 1. A communications channel or simple networks. path between two devices capable of carry- ing electrical current. See also Cisco Certified Design Professional. 2. A set of components connected to per- form a specific task. Cisco Certified Design Professional circuit switching A temporary commu- Abbreviated CCDP. A certification from nications connection established as re- Cisco designed to evaluate knowledge of quired between the sending and receiving complex networks based on Cisco LAN nodes. Circuit switching is often used in and WAN routers and LAN switches. modem communications over dial-up tele- See also Cisco Certified Design Associate. phone lines. It is also used in some privately maintained communications networks. Cisco Certified Internetworking See also message switching; packet Expert Abbreviated CCIE. An advanced switching; virtual circuit. certification from Cisco offered in three 71 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 72 Thursday, May 4, 2000 11:59 AM Cisco Certified Network Associate areas: CCIE-Routing and Switching, CCIE- made by Cisco, and its Internetwork Oper- Internet Service Provider (ISP) Dial, and ating System (IOS) is quickly becoming an CCIE-WAN Switching. industry standard that other vendors are in- corporating into their own products. Cisco Certified Network Associate Abbreviated CCNA. A certification from For more information on Cisco, see Cisco designed to evaluate network support www.cisco.com. knowledge. CiscoView Device management soft- See also Cisco Certified Network ware for Cisco networking devices. Cisco- Professional. View provides troubleshooting and device monitoring functions and can be used in Cisco Certified Network Professional conjunction with Simple Network Manage- Abbreviated CCNP. An advanced certifica- ment Protocol (SNMP) products. tion from Cisco designed to evaluate net- work support knowledge. See also Simple Network Management Protocol. See also Cisco Certified Network Associate. Ciscoworks A set of management appli- cations from Cisco Systems, Inc., designed Cisco Discovery Protocol Abbreviated for use with Cisco routers. CDP. A proprietary Cisco protocol that runs on all hardware made by Cisco, in- CISSP See Certified Information Sys- cluding routers, switches, access servers, tems Security Professional. and bridges. CIX See Commercial Internet Exchange. CDP is both protocol- and media- independent. A router running CDP can CJD See Certified Java Developer. advertise its existence to other routers and can discover a directly connected neigh- CJP See Certified Java Programmer. bor’s port and hostname information, as cladding The transparent material, usu- well as hardware model number and sys- ally glass, that surrounds the core of an op- tem capabilities. tical fiber. Cladding has a lower refractive Cisco Extended Bus Abbreviated Cx- index than the core and so prevents the light Bus. The extended bus used in routers from signal from spreading out due to modal dis- Cisco Systems, Inc. persion, by reflecting the signal back into the central core. This helps to maintain the See also ciscoBus; switch processor signal strength over long distances. Cisco Systems, Inc. The world’s lead- See also dispersion. ing manufacturer of routers and internet- working hardware and software products. Class A certification An FCC certifica- More than 80 percent of the backbone rout- tion for computer equipment, including ers currently in use on the Internet were mainframe computers and minicomputers 72 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 73 Thursday, May 4, 2000 11:59 AM Classless Inter-Domain Routing destined for industrial, commercial, or of- bits are used to define 16,384 networks, each fice use, rather than for personal use at with as many as 65,535 hosts attached. Ex- home. The Class A commercial certifica- amples of Class B networks include Microsoft tion is less restrictive than the Class B and Exxon. All Class B networks are in use, certification for residential use, because it and no more are available. assumes that most residential areas are See also address classes; IP address. more than 30 feet from any commercial computer equipment. Class C network In the IP addressing See also Class B certification. scheme, a smaller network. The 3 high-or- der bits are always 110, and the remaining Class A network In the IP addressing bits are used to define 2,097,152 networks, scheme, a very large network. The high-or- but each network can have a maximum of der bit in a Class A network is always zero, only 254 hosts. Class C networks are still leaving 7 bits available to define 127 net- available. works. The remaining 24 bits of the address allow each Class A network to hold as See also address classes; IP address. many as 16,777,216 hosts. Examples of Class A networks include General Electric, Class D network In the IP addressing IBM, Hewlett-Packard, Apple Computer, scheme, a special multicast address that Xerox, Digital Equipment Corporation, cannot be used for networks. The 4 high-or- and MIT. All the Class A networks are in der bits are always 1110, and the remaining use, and no more are available. 28 bits allow access to more than 268 mil- lion possible addresses. See also address classes; IP address. See also address classes; IP address. Class B certification An FCC certifica- tion for computer equipment, including Class E network In the IP addressing PCs, laptops, and portables destined for use scheme, a special address reserved for ex- in the home rather than in a commercial set- perimental purposes. The first 4 bits in the ting. Class B levels of radio frequency inter- address are always 1111. ference (RFI) must be low enough so that See also address classes; IP address. they do not interfere with radio or televi- sion reception when there is more than one classes In Novell Directory Services, an wall and 30 feet separating the computer object can be defined as an instance of from the receiver. Class B certification is an object class. Classes include User, more restrictive than the commercial Class Group, Printer, Print Server, Computer, A certification. and so on. See also Class A certification. Classless Inter-Domain Routing Ab- Class B network In the IP addressing breviated CIDR, pronounced “cider.” An scheme, a medium-sized network. The 2 high- interim solution to the problem that the In- order bits are always 10, and the remaining ternet is running out of addresses. 73 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 74 Thursday, May 4, 2000 11:59 AM cleartext Blocks of Class C addresses are assigned to A client may be a PC or a workstation on a a site based on the number of addresses that network using services provided from the site requires, to prevent wasted addresses. network file server, or it may be that part of Also, the Class C address space is divided an application program that runs on the into four major areas—Europe, North workstation supported by additional soft- America, Central and South America, and ware running on the server. Asia and the Pacific—and each zone is as- One of the most familiar clients is the Web signed 32 million addresses. browser. CIDR networks are often described as See also client/server architecture; DOS cli- “slash x” networks; the x represents the ent; Macintosh client; OS/2 client; Unix number of bits in the IP address range con- client; Windows client. trolled by the granting authority. For exam- ple, a Class C network in CIDR terms client application In OLE, the applica- becomes a slash 24 network. tion that starts a server application to ma- See also address classes; IP address. nipulate linked or embedded information. cleartext Text that has not been encrypt- client pull A mechanism used on the In- ed in any way and that can be intercepted ternet whereby a client application, usually and read easily while in transit; usually ap- a Web browser, initiates a request for ser- plied to an unencrypted password. vices from a Web site. See also plaintext. See also server push. clear text authentication An authenti- Client Services for NetWare A soft- cation method that encodes user name and ware package included with Microsoft password information according to a freely Windows 2000 that connects a Windows available 64-bit encoding utility. 2000 client to a Novell NetWare file server. See also challenge-response authentica- tion; encryption. client/server architecture A comput- ing architecture that distributes processing Clear to Send Abbreviated CTS. A between clients and servers on the network. hardware signal defined by the RS-232-C standard that indicates that the transmis- In the past, traditional computing has relied sion can proceed. on a hierarchical architecture based on non- programmable dumb terminals connected See also RS-232-C; Request to Send. to a mainframe computer. In this scheme, the database was on the same computer CLEC See Competitive Local Exchange that was running the application. A client/ Carrier. server approach replaces this structure by client A device or application that uses dividing the application into two separate the services provided by a server. parts: a front-end client and a back-end 74 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 75 Thursday, May 4, 2000 11:59 AM clock server, usually referred to as a client and a server may also be a minicomputer or a server. mainframe computer. The client component provides the user Typically, a client/server approach reduces with the power to run the data-entry part of network traffic, because relatively small the application, and this part of the client is amounts of data are moved over the net- usually optimized for user interaction with work. This is in sharp contrast to the typical the system. network, in which entire files are constantly The server component, which can be either being transmitted between the workstation local or remote, provides the data manage- and the file server. ment, administration, and system security Database applications were some of the features and manages information sharing first to embrace the client/server concept, with the rest of the network. particularly those using Structured Query In other words, clients request information Language (SQL). SQL has grown into an in- from the servers, and the servers store data dustry standard database language; it is rel- and programs and provide network services atively easy to implement, it is robust and to clients. powerful, and it is easy for users to learn. Client/server architecture can sustain sever- See also network computer; thin client. al levels of organizational complexity, in- cluding the following: client-side caching See offline files. I Stand-alone (non-networked) client ap- Clipper chip A low-cost encryption de- plications, such as local word processors vice backed by the U.S. federal government. I Applications that run on the client but The chip would allow businesses to trans- request data from the server, such as mit encoded messages, but at the same time, spreadsheets allow certain government agencies to inter- I Programs that use server capabilities to cept and decode the messages if criminal ac- share information among network users, tivities were suspected. Needless to say, this such as electronic mail systems proposal has generated a lot of intense dis- I Programs in which the physical search of cussion, particularly from civil rights records takes place on the server, while a groups concerned with an individual’s right much smaller program running on the cli- to privacy and other ethical issues; other ent handles all user-interface functions, potential users want access to the best avail- such as database applications able encryption systems, not just those put Client/server computing lightens the pro- forward by the government. cessing load for the client PCs, but increases CLNP See Connectionless Network the load on the server. For this reason, serv- Protocol. er computers tend to have larger and faster hard-disk drives and much more memory clock An electronic circuit that generates installed than conventional file servers. The regularly spaced timing pulses at speeds up 75 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 76 Thursday, May 4, 2000 11:59 AM clock-multiplying to millions of cycles per second. These puls- See also Advanced Micro Devices, Inc.; es are used to synchronize the flow of infor- Cyrix. mation through the computer’s internal communications channels. closed architecture A design that does See also clock speed. not allow for easy, user-supplied additions. This term is often used to describe some of clock-multiplying A mechanism used by the early Macintosh computers, which did some Intel processors that allows the chip not allow easy expansion of the system with to process data and instructions internally add-in cards. Closed architecture can also at a speed different from that used by the refer to a computer design whose specifica- rest of the system. tions are not published or generally avail- able, making it impossible for third-party clock speed The internal speed of a com- companies to provide products that work puter or processor, normally expressed in with the computer. megahertz (MHz). Also known as clock rate. See also open architecture. The faster the clock speed, the faster the computer will perform a specific operation CLP See Cell Loss Priority; Certified (assuming the other components in the Lotus Professional. system, such as disk drives, can keep up with the increased speed). CLS See Certified Lotus Specialist. The Intel 8088 processor used in the original CLTP See Connectionless Transport IBM PC had a clock speed of 4.77MHz— Protocol. painfully slow when compared with speeds used by current processors, which can run at cluster controller An IBM or IBM-com- clock speeds of several hundred MHz. patible device located between a group of 3270 terminals and the mainframe comput- clone Hardware that is identical in func- er. The cluster controller communicates be- tion to an original. tween the computer and the terminals using For example, an IBM clone is a PC that uses SDLC (Synchronous Data Link Control) or an Intel (or similar) microprocessor and a bisynchronous communications protocol. functions in the same way as the IBM PC standard. A Macintosh clone functions in clustering A fault-tolerant technology the same way as a computer manufactured designed to keep server availability at a very by Apple Computer, Inc. high level. Although most clones do perform as in- Clustering groups servers and other net- tended, small internal differences can cause work resources into a single system; if one problems in some cases. It can be difficult to of the servers in the cluster fails, the other ensure consistency of components and level servers can take over the workload. Clus- of operation when using a number of clones tering software also adds a load-balancing purchased over a long period of time. feature to make sure that processing is 76 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 77 Thursday, May 4, 2000 11:59 AM codec distributed in such as way as to optimize CNP See Certified Network system throughput. Professional. CLV See constant linear velocity. coax See coaxial cable. CMIP See Common Management Infor- coaxial cable Abbreviated coax, pro- mation Protocol. nounced “co-ax.” A high-capacity cable used in networking that contains a solid in- CMIS See Common Management Infor- ner copper conductor surrounded by plastic mation Services. insulation, and an outer braided copper or CMOS See Complementary Metal- foil shield. Oxide Semiconductor. Coaxial cable is used for broadband and baseband communications networks (and CNA See Certified Novell Administrator. for cable television), because the cable is CNE See Certified Novell Engineer. usually free from external interference and permits high transmission rates over long CNEPA See Certified Novell Engineer distances. Professional Association. See also fiber-optic cable; RG-58; RG-59; CNI See Certified Novell Instructor. RG-62; thick Ethernet; thin Ethernet. COAXIAL CABLE codec 1. Acronym for coder/decoder, transmission and then converts those dig- pronounced “coe-deck.” A device that ital signals back into analog signals at the converts analog signals (such as voice or receiving end. video) into a digital bit stream suitable for 77 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 78 Thursday, May 4, 2000 11:59 AM Code Division Multiple Access 2. Acronym for compression/decompres- message on the same channel at exactly the sion, pronounced “coe-deck.” An overall same moment. term to describe the hardware and software See also Carrier Sense Multiple Access/ used in processing animation, digital video, Collision Detection; token-ring network. and stereo-quality audio. See also lossless compression; lossy colon The symbol used after the protocol compression. name in a URL. See also Uniform Resource Locator. Code Division Multiple Access Abbre- viated CDMA, also known as spread spec- COM See Common Object Model; Com- trum. A digital cellular standard approved ponent Object Model. by the Telecommunications Industry Asso- ciation (TIA) in 1993 and known as IS-95. COM 1–4 See COM port. CDMA combines both data and voice into command interpreter See command a single wireless network and can provide processor. users with digital voice services, voice mail, text messaging, and caller ID. CDMA also command line Any interface between increases system capacity up to 10 times the user and the command processor that that of analog systems. allows you to enter commands from the keyboard for execution by the operating See also Advanced Mobile Phone Service; system. Cellular Digital Packet Data; wireless communications. See also graphical user interface; shell; text mode. cold boot The computer startup process that begins when you turn on power to the command-line argument A parameter computer. You are doing a cold boot when that alters the default mode of a command. you first turn on your computer. A cold In many operating systems, a command- boot might also be necessary if a program line argument is one or more letters or or the operating system crashes and freezes numbers preceded by the / (slash) charac- entirely. If your keyboard is operational, a ter. In Unix, a command-line argument warm boot may suffice. may be called an option or a flag and is See also boot; warm boot. usually a single character preceded by a hy- phen (as in -r). With some commands, you collaboration software A set of net- can group several switches. Sometimes work-based applications that let users share called a command-line switch. information quickly and easily. See also command line. See also whiteboard. command processor The part of the collision In networking or communica- operating system that displays the com- tions, an attempt by two nodes to send a mand prompt on the screen, interprets and 78 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 79 Thursday, May 4, 2000 11:59 AM Common Hardware Reference Platform executes all the commands and filenames oriented technology and system adminis- that you enter, and displays error messages tration issues. when appropriate. Also called the com- mand interpreter. The command processor Common Gateway Interface Abbrevi- also contains the system environment. ated CGI. A standard way that programs can interface with Web servers and allow command prompt A symbol (character them to run applications such as search en- or group of characters) on the screen that gines and to access databases and other lets you know that the operating system is back-end applications. available and ready to receive input. CGI defines the field specifics and control Commercial Internet Exchange Ab- tags to be placed in an HTML document, breviated CIX, pronounced “kicks.” A con- the environment variables where the Web nection point between ISPs. server places information for use by scripts, A location where top-tier ISPs maintain the and the flow of information between client routers used to route packets between their Web browser, the server, and the Web serv- respective network segments. er scripts. CGI is platform-independent. Common Application Environment See also HyperText Markup Language; script; Web server. Abbreviated CAE. A set of standards, devel- oped by X/Open for application develop- Common Internet File System Abbre- ment, including standards for the operating system, compilers, software development viated CIFS. A file system supported by Mi- tools, data management, networking, and crosoft, DEC, Data General, SCO, and the graphical user interface. others, which allows users and organiza- tions to run file systems over the Internet. common carrier A communications CIFS is an extension to Microsoft’s Server company, such as AT&T or MCI, that pro- Message Blocks (SMB) file-sharing proto- vides data and voice telecommunication col and allows users to share files over the services to the general public. Internet in the same way that they share See also Postal Telephone and Telegraph. files using networking services on Windows clients. Common Desktop Environment Ab- breviated CDE. A set of specifications de- See also WebNFS. veloped by the Common Open Software Environment (COSE) that defines an API Common Hardware Reference for a common Unix graphical user inter- Platform Abbreviated CHRP. An open face. The specifications cover the interop- hardware architecture, based on the Power- erability of applications across different PC and originally defined by IBM, that en- hardware platforms, multimedia and sures compatibility between systems made networking operations, as well as object- by different manufacturers. 79 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 80 Thursday, May 4, 2000 11:59 AM Common Management Information Protocol Common Management Information Common Object Request Broker Protocol Abbreviated CMIP. The Open Architecture Abbreviated CORBA. A Systems Interconnection (OSI) manage- standard from the Object Management ment information protocol for network Group (OMG), whose members include monitoring and control information, desig- Sun Microsystems, Hewlett-Packard, DEC, nated ISO 9596. and IBM, that enables communications be- tween distributed object-oriented applica- CMIP includes fault management, configu- tions, regardless of the language they are ration management, performance manage- written in and the hardware platform on ment, and security and accounting which they run. management. It is not widely available. CORBA uses Object Request Brokers to set See also Common Management Informa- up communications between objects and to tion Services; Simple Network Manage- invoke methods on behalf of these objects. ment Protocol. CORBA competes with Microsoft’s Dis- Common Management Information tributed Component Object Model Services Abbreviated CMIS. The Open (DCOM) and ActiveX technology. Systems Interconnect (OSI) standard func- See also Distributed Component Object tions for network monitoring and control. Model. See also Common Management Informa- tion Protocol. Common Open Software Environ- ment Abbreviated COSE, pronounced Common name In Novell Directory “cosy.” An industry group consisting of al- Services, every object has a name that is most 100 members, organized to develop a unique within its context in the directory standard graphical user interface for Unix, structure. This name is known as the Com- known as the Common Desktop Environ- mon name when it refers to users, nodes, or ment, or CDE. Original members included servers. Sun Microsystems, Hewlett-Packard, IBM, SCO, and the UNIX Systems Group. See also Distinguished Name. Common Programming Interface for Common Object Model Abbreviated Communications Abbreviated CPI-C. COM. A specification from Microsoft and A cross-platform API from IBM that inter- DEC to provide cross-platform interopera- faces to the Advanced Program-to-Program bility across non-Windows platforms. Communications (APPC) environment. COM was developed to allow networks us- CPI-C is designed to support a common en- ing Microsoft’s OLE technology to commu- vironment for application execution across nicate with networks using DEC’s Object- several IBM operating systems, including Broker technology. MVS, VS, OS/400, and OS/2-based systems. 80 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 81 Thursday, May 4, 2000 11:59 AM Compact Disc-Interactive See also Advanced Peer-to-Peer Network- communications satellite A satellite in ing; Advanced Program-to-Program geostationary orbit, acting as a microwave Communications; Advanced Interactive relay station. The satellite receives signals Executive; Multiple Virtual Storage. from a groundstation, amplifies them, and retransmits them on a different frequency common share In Microsoft Windows to another groundstation. 2000, system elements automatically shared by default when the operating sys- See also downlink; propagation delay; tem is installed or upgraded. Many com- uplink. mon shares are also hidden shares. compact disc Abbreviated CD. A non- See also default shares; hidden share; magnetic, polished, optical disc used to store share; sharing. large amounts of digital information. A CD can store approximately 650MB of informa- communications/modem server In a tion, equivalent to more than 1700 low- network, a server equipped with a bank of density floppy disks. This storage capacity modems, which can be shared by users for translates into approximately 300,000 pages outgoing calls. of text or 72 minutes of music, all on a single See also access server. 4.72-inch disc. communications parameters Any of Digital information is stored on the com- several settings required to allow comput- pact disc as a series of microscopic pits and ers to communicate successfully. In asyn- smooth areas that have different reflective chronous transmissions, commonly used in properties. A beam of laser light shines on modem communications, the settings for the disc so that the reflections can be detect- baud rate, number of data bits, number of ed and converted into digital data. stop bits, and parity parameters must all be See also CD-Recordable; CD ReWritable; correct. CD-ROM Extended Architecture; Compact communications protocol 1. A stan- Disc-Interactive; Compact Disc—Read- dard way of communicating between com- Only Memory; digital video disc. puters or between computers and terminals. Communications protocols vary in com- Compact Disc-Interactive Abbreviat- plexity, ranging from Xmodem, a simple ed CD-I. A hardware and software stan- file-transfer protocol used to transfer files dard disc format for data, text, audio, still from one PC to another, to the seven-layer video images, and animated graphics. The OSI Reference Model used as the theoretical standard also defines methods of encoding basis for many large, complex computer and decoding compressed data, as well as networks. displaying data. 2. A hardware interface standard, such as See also compact disc; Compact Disc— RS-232-C. Read-Only Memory. 81 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 82 Thursday, May 4, 2000 11:59 AM Compact Disc—Read-Only Memory Compact Disc—Read-Only Memory as well as access to DEC’s highly regarded Abbreviated CD-ROM. A high-capacity, hardware and software products. optical storage device that uses the same Compaq also shook up the computer indus- technology used to make ordinary music try when it introduced the first PC that cost discs to store large amounts of information. less than $1,000. A single 4.72-inch disc can hold up to 650MB. For more information about Compaq, see www.compaq.com. CD-ROMs are important components of multimedia applications. They are also compatibility The extent to which a giv- used to store encyclopedias, dictionaries, en piece of hardware or software conforms and other large reference works, as well as to an accepted standard, regardless of the libraries of fonts and clip art for desktop original manufacturer. publishing. CD-ROMs have replaced flop- In hardware, compatibility is often ex- py disks as the distribution mechanism for pressed in terms of widely accepted mod- software packages, including network op- els—this designation implies that the device erating systems and large applications; you will perform in the same way as the stan- can load the whole package from a single dard device. compact disc, and you can load an operat- ing system from a set of discs. In software, compatibility is usually de- A CD-ROM uses the constant linear veloc- scribed as the ability to read data file formats ity data encoding scheme to store informa- created by another vendor’s software or the tion in a single, spiral track, divided into ability to work together and share data. many equal-length segments. To read data, See also plug-compatible. the CD-ROM disk drive must increase the rotational speed as the read head gets closer Competitive Local Exchange Carrier to the center of the disk and must decrease Abbreviated CLEC. A term coined from the as the head moves back out. Telecommunications Act of 1996 to de- See also CD-Recordable; Compact Disc-In- scribe the deregulated, competitive phone teractive; constant angular velocity; High companies that will be able to offer local ex- Sierra specification. change service as well as long distance and international services, Internet access, and Compaq Computer Corporation One cable and video on-demand services. of the world’s largest computer manufac- See also Incumbent Local Exchange Carri- turers, Compaq recently acquired the Digi- er; Local Exchange Carrier. tal Equipment Corporation (DEC), which boosted the company into the top three compiler A program that converts a set along with IBM and Hewlett-Packard. of program language source code state- By acquiring DEC, Compaq gained a ments into a machine-readable form suit- world-wide service and support structure, able for execution by a computer. 82 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 83 Thursday, May 4, 2000 11:59 AM compressed file Most compilers do much more than this, COM components can be written in any however; they translate the entire program programming language and can be added into machine language, while at the same to or removed from a program without time, they check your source code syntax requiring recompilation. COM is the foun- for errors and then post error messages or dation of the Object Linking and Embed- warnings as appropriate. ding (OLE) and ActiveX specifications. See also just-in-time compiler. See also ActiveX; Common Object Re- quest Broker Architecture; Distributed Complementary Metal-Oxide Component Object Model. Semiconductor Abbreviated CMOS, pronounced “See-moss.” A type of inte- COM port In MS-DOS and Microsoft grated circuit used in processors and for Windows, the device name used to denote a memory. Because CMOS devices operate at serial communications port. In versions of very high speeds and use little power, they MS-DOS after 3.3, four COM ports are generate little heat. In the PC, battery- supported: COM1, COM2, COM3, and backed CMOS memory is used to store op- COM4. Earlier versions support only erating parameters, such as the hard disk COM1 and COM2. type, when the computer is switched off. compound document A document file complex instruction set computing that consists of information created by two Abbreviated CISC, pronounced “sisk.” A or more applications, for example, a data- processor that can recognize and execute base document embedded within a word- more than 100 different assembly-language, processing document. or low-level, instructions. CISC processors can be powerful, but the instructions take a Object Linking and Embedding (OLE) can high number of clock cycles to execute. link and embed documents and can be used to start the appropriate application This complexity is in contrast to the sim- program. plicity of reduced instruction set computing (RISC) processors, in which the number of See also Object Linking and Embedding. available instructions has been cut to a min- imum. RISC processors are common in compressed file A file that has been workstations and can be designed to run up processed by a special utility so that it oc- to 70 percent faster than CISC processors. cupies as little hard-disk space as possible. When the file is needed, the same program See also assembly language; reduced decompresses the file back into its original instruction set computing. form so that it can be read by the computer. Component Object Model Abbreviat- Popular compression techniques include ed COM. A specification from Microsoft schemes that replace commonly occurring that defines how objects interact in the sequences of characters by tokens that take Windows environment. up less space. Some utilities use Huffman 83 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 84 Thursday, May 4, 2000 11:59 AM Compression Control Protocol coding to shrink a file, and others use adap- Computer Associates International tive Lempel-Ziv coding. Abbreviated CAI. A leading supplier of en- See also data compression; file compres- terprise applications and services to the cor- sion; PKZip; WinZip; ZIP file. porate world, including defense contractors and Fortune 500 companies. Compression Control Protocol Ab- CAI’s rapid expansion in recent years has breviated CCP. A protocol used with Point- been due to an aggressive acquisitions pol- to-Point Protocol (PPP) to configure, en- icy that has led to the incorporation of able, and disable data compression algo- Legent and Cheyenne Software and to a rithms at both ends of the point-to-point joint venture with Fujitsu that created the connection. CCP can support different object-oriented database Jasmine. compression algorithms in each direction of the connection. CAI currently enjoys success with Unicenter TNG, a collection of applications and tools See also Point-to-Point Protocol. used to manage enterprise computing. CompuServe Abbreviated CIS. A major For more information on CAI, see provider of online services including e-mail, www.cai.com. file downloading, forums on a variety of top- ics, chat rooms, and Internet access, as well Computer Emergency Response as commercial services offered to a large Team Abbreviated CERT. Founded in number of business users. In 1998, Compu- 1988 at Carnegie-Mellon University, Serve was bought by America Online. CERT works with the Internet community to increase awareness of security issues; it For more information on CompuServe, see conducts research into improving existing www.compuserve.com. systems and provides 24-hour technical as- computation bound A condition in sistance service for responding to security which the speed of operation of the proces- incidents. sor actually limits the speed of program ex- Computer Management In Microsoft ecution. The processor is limited by the Windows 2000, the administrative tool number of arithmetic operations it can used to manage a local or remote computer. perform. Computer Management is a Microsoft See also input/output bound. Management Console (MMC) snap-in and replaces several Windows NT administra- computer account In Microsoft Win- tive tools, including Server Manager, User dows 2000, an object in the Security Ac- Manager for Domains, and Disk Adminis- counts Manager that describes a specific trator. computer within a network domain. A computer account is added for each node See also Active Directory; Microsoft Man- added to the domain. agement Console; snap-in. 84 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 85 Thursday, May 4, 2000 11:59 AM concurrent license computer name 1. In Microsoft Win- CSRG was home to some remarkable pro- dows NT, a name of up to 15 uppercase let- grammers over the years and introduced ters that identifies a specific computer to the into Unix many of the fundamental features other computers on the network. The com- we take for granted. The last BSD release, puter name is created during installation 4.4BSD, was made during 1993, and the and must be unique within the workgroup group was disbanded shortly afterward. or domain; you can change the computer name using the Network applet in Control concentrator A repeater or hub that Panel. joins communications channels from sever- 2. In NetBIOS, a name of up to 15 char- al network nodes. Concentrators are not acters that uniquely identifies a worksta- just simple wire-concentration centers, but tion to computers and users. Once a also provide bridging, routing, and other computer is named, NetBIOS can establish management functions. sessions between computers and use those concurrent When two or more programs links to exchange data between systems. (processes) have access to the processor at These exchanges can be either NetBIOS the same time and must share the system re- requests or Server Message Block (SMB) sources, they are said to be “running con- data. Network applications use NetBIOS names to locate resources, although the currently.” Because a computer can Windows Sockets API is now more com- perform operations so quickly, the process- monly used. es seem to be occurring at the same time, al- though actually they are not. See also NetBIOS; WinSock. See also multiprocessing; task; task Computer object In NetWare Directory switching; thread. Services, a leaf object representing a comput- er on the network. The Computer object’s concurrent license A software license properties can contain information such as that allows more than one person at a com- the computer’s physical serial number and pany to share an application over a net- the name of the person to whom the com- work, providing that, at any given time, puter is currently assigned. only one person is using it. See also leaf object; Novell Directory Different versions of concurrent licensing Services. allow a fixed number of people in an office to share one copy of an application and al- Computer Systems Research Group low the application to be used on both desk- Abbreviated CSRG. The University of Cal- top and portable PCs, rather than run only ifornia, Berkeley, group responsible for the from the file server. development of the Berkeley Software Dis- tribution (BSD). See also application metering. 85 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 86 Thursday, May 4, 2000 11:59 AM CONFIG.SYS CONFIG.SYS In MS-DOS and OS/2, a administration tasks, often performed by special text file containing settings that con- the network administrator, including: trol the way the operating system works. I Maintaining a hardware database contain- In MS-DOS, the CONFIG.SYS file may con- ing details of routers, bridges, and connec- tain 10 to 20 lines of entries. In OS/2, it is tions so that changes in the network can be likely to contain between 70 and 100 lines of made quickly in the event of a failure configuration information. CONFIG.SYS I Adding and removing workstations and must be in the root directory of the default users to the network as needed boot disk, normally drive C, and is read once as the system starts running. I Adding and configuring new servers and cabling systems as the network expands configuration The process of establish- See also Desktop Management Interface. ing your own preferred setup for an appli- cation, expansion board, computer system, configuration register A 16-bit, user- or network. Most current software can es- configurable value that determines how a tablish a configuration for you automati- Cisco router functions during router initial- cally, although you may need to adjust that ization. You can configure information in configuration to get the best results. hardware by using jumpers and in software See also Desktop Management Interface; by specifying a hexadecimal number in con- Plug and Play. figuration commands. configuration file A file, created by an congestion An excessive amount of traf- application or an operating system, con- fic on the network, causing messages to be taining configuration information specific blocked for long periods of time and ad- to your own computing environment. Ap- versely affecting network performance. plication configuration files may have a file- You may see a very slow response from a name extension of CFG or SET; Windows server, or you may see an error message tell- configuration files use the INI filename ing you that no ports are available at the extension. present time for the service or host you are If you accidentally erase an application’s requesting. configuration file, the program will return See also Ethernet meltdown. to using its default settings. Although the program will continue to function, its con- connectionless A protocol in which the figuration settings may not be suitable for source and destination addresses are in- your system. cluded inside each packet so that a direct See also AUTOEXEC.BAT; CONFIG.SYS; connection between sender and receiver or NET.CFG. an established session between nodes is not required for communications. In a connec- configuration management A term tionless service, data packets may not reach covering a wide range of network their destination in the same order in which 86 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 87 Thursday, May 4, 2000 11:59 AM connection speed they were sent. UDP is a connectionless other applications and processes that use transport service. the server connections. See also connection-oriented; User Data- connection-oriented A term used to de- gram Protocol. scribe a communications model that goes through three well-defined stages: estab- Connectionless Network Protocol lishing the connection, transferring the da- Abbreviated CLNP. An Open Systems In- ta, and releasing the connection. Analogous terconnect (OSI) protocol that provides the to a voice telephone call. In a connection- OSI Connectionless Network Service for oriented service, data packets always reach the delivery of data. It uses datagrams that their destination in the same order in which include addressing information to route they were sent. TCP is a connection-orient- network messages. CLNP is used for LANs ed transport service. rather than WANs. CLNP is the OSI equiv- alent of IP (Internet Protocol). See also connectionless; Transmission Control Protocol. See also Connection-Oriented Network Service. Connection-Oriented Network Connectionless Transport Protocol Service Abbreviated CONS. A data transmission service in which data is only Abbreviated CLTP. An Open Systems In- transmitted once a connection has been es- terconnect (OSI) protocol that provides tablished. Asynchronous Transfer Mode end-to-end transport data addressing and (ATM) is a connection-oriented service. error correction, but does not guarantee de- livery or provide any flow control. CLTP is See also Connectionless Network Proto- the OSI equivalent of UDP. col; Connectionless Transport Protocol. See also Connection-Oriented Network Service; User Datagram Protocol. connection speed The speed of a data communications circuit. Some circuits are Connection Admission Control Ab- symmetrical and can maintain the same breviated CAC. An Asynchronous Transfer speed in both directions; others are asym- Mode (ATM) function that determines metrical and use a faster speed in one direc- whether a virtual circuit connection request tion, usually the downstream side. Table C.1 will be accepted. compares the connection speeds available for several technologies. See also Asynchronous Transfer Mode. See also Asymmetric Digital Subscriber connection number A number assigned Line; cable modem; High-Bit-Rate Digital to a workstation that attaches to a server; it Subscriber Line; Integrated Services Digi- may be a different number each time the tal Network; modem; Single-Line Digital workstation attaches. Connection numbers Subscriber Line; Very-High-Bit-Rate Digital are also assigned to print servers, as well as Subscriber Line. 87 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 88 Thursday, May 4, 2000 11:59 AM connectivity TABLE C.1 CONNECTION SPEEDS Technology Speed Distance Limitation Conventional 56Kbps downstream, up to None modem 33.6Kbps upstream ISDN Up to 128Kbps symmetric 18,000 ft Cable modem Up to 30Mbps downstream, to 30 mi 10Mbps upstream ADSL 1.5 to 8Mbps downstream, to 18,000 ft 1.544Mbps upstream SDSL 1.544 to 2.048Mbps symmetric 10,000 ft HDSL 1.544 to 2.048Mbps symmetric 15,000 ft (over 3 phone lines) VDSL 13 to 52Mbps downstream, 1.5 to 4,500 ft 2.3Mbps upstream connectivity The degree to which any Conseil Européen pour la Researche given computer or application can cooper- Nucléaire Abbreviated CERN. The Eu- ate with other network components pur- ropean Laboratory for Particle Physics lo- chased from other vendors, in a network cated in Geneva, Switzerland, where Tim environment in which resources are shared. Berners-Lee and associates created the com- munications protocols that led to the World connect time The period of time during Wide Web. which a user is logged on to the network. For more information on CERN, see ConnectView An application with a www.cern.ch. graphical user interface used to manage NetWare Connect and Novell Internet Ac- console Sometimes abbreviated cons. cess Server (NIAS) communication servers. The monitor and keyboard from which the server or host computer activity can be CONS See Connection-Oriented Net- monitored. work Service. Certain operating system commands and cons See console. utilities must be executed from the console 88 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 89 Thursday, May 4, 2000 11:59 AM container administrator device; they will not operate from a work- Consultative Committee for Interna- station. In some systems, the console is a tional Telephony and Telegraphy Ab- virtual device that can be invoked from any breviated CCITT. An organization based in workstation by a network administrator Geneva that develops worldwide data com- with the appropriate rights and privileges. munications standards. Three main sets of standards have been established: constant angular velocity Abbreviat- I CCITT Groups 1–4 standards apply to ed CAV. An unchanging speed of rotation. facsimile transmissions. Hard disks use a CAV encoding scheme. The constant rate of rotation means that I CCITT V series of standards apply to mo- sectors on the disk are at the maximum den- dems and error detection and correction sity along the inside track of the disk. As the methods. read/write heads move outward, the sectors I CCITT X series standards apply to LANs. must spread out to cover the increased track Recommendations are published every four circumference, and therefore the data- years. In 1993, after a reorganization, the transfer rate falls off. name was changed to International Tele- See also constant linear velocity. communication Union (ITU), and even though ITU now creates recommendations Constant Bit Rate Abbreviated CBR. A and standards, you will still hear the CCITT type of Asynchronous Transfer Mode standards mentioned. (ATM) service reserved for voice or video See also International Telecommunication or other data that must be transmitted at a Union. constant rate and are intolerant of data loss. container One of the Java programming See also Asynchronous Transfer Mode; language classes that can contain graphical Available Bit Rate; Unspecified Bit Rate; user interface components. Components in Variable Bit Rate. a container usually appear within the boundaries of that container. For example, constant linear velocity Abbreviated the classes Dialog, Frame, and Window are CLV. A changing speed of rotation. CD- all containers. ROM disk drives use a CLV encoding See also Java. scheme to make sure that the data density remains constant. Information on a com- container administrator In Novell Di- pact disc is stored in a single, spiral track, rectory Services, an administrator who is divided into many equal-length segments. granted rights to a container object and all To read the data, the CD-ROM disk drive the objects that the container holds. A con- must increase the rotational speed as the tainer administrator can be exclusive, indi- read head gets closer to the center of the disc cating that no other administrator is and decrease as the head moves back out. allowed access to that container. See also constant angular velocity. See also container object; leaf object. 89 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 90 Thursday, May 4, 2000 11:59 AM container object container object In Novell Directory other programs loaded onto your system Services, an object that can contain other must halt. objects and that is used to represent a logi- control character A nonprinting char- cal or physical organizational element with- acter with a special meaning. in a company, such as a department or a division. The Tree, Country, Organization, Control characters, such as Carriage Re- and Organizational Unit objects are all con- turn, Line Feed, Bell, or Escape, perform a tainer objects. specific operation on a terminal, printer, or See also container administrator; Country communications line. They are grouped to- object; leaf object; Organization object; Or- gether as the first 32 characters in the ASCII ganizational Unit object; Tree object. character set; see Appendix C for details. You can type a control character from the container security equivalence See keyboard by pressing and holding the Ctrl implied security equivalence. key while you simultaneously press anoth- er key. For example, if you press and hold contention The competition between the Ctrl key and then press C, you generate transmitting nodes for access to communi- Ctrl+C, also known as Break. Control cations lines or network resources. The first character sequences are often used inside device to gain access to a channel takes con- application programs as menu command trol of the channel. In the event of a colli- shortcuts. sion, when two nodes attempt to transmit at the same time, some arbitration scheme See also American Standard Code for must be invoked. Information Interchange; Extended Binary Coded Decimal Interchange Code; See also Carrier Sense Multiple Access/ Unicode. Collision Detection; token passing. control code A sequence of one or more context In Novell Directory Services, an characters used for hardware control; also object’s location within the Directory tree. known as setup strings or escape sequences. The context is the full path to the container Control codes are used with printers, mo- object in which the object is placed. If an dems, and displays. Printer control codes object is moved from one container to an- often begin with an escape character, fol- other, it has changed contexts. lowed by one or more characters that the See also container object; leaf object. printer interprets as commands it must per- form rather than as text it must print. context switching Switching from one program to another without ending the first Control Panel In Microsoft Windows, a program. Context switching allows you to special system folder that contains applets operate several programs at the same time; used to look at or change configuration in- but it differs from true multitasking in that formation. Each applet manages a single when you are using one program, all the task such as adding or removing a program 90 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 91 Thursday, May 4, 2000 11:59 AM cooperative multitasking from your system, setting up a connection See also expanded memory; extended to the Internet, or changing display settings. memory; high memory area; memory See also Network and Dial-up management; protected mode. Connections. convergence The synchronization pro- Controlled Access Unit Abbreviated cess that a network must go through imme- CAU. An intelligent Multistation Access diately after a routing change takes place on Unit (MAU) or multiport wiring hub for a the network. Convergence time is the time token-ring network that allows ports to be required to update all the routers on the net- switched on and off. work with routing information changes. controllerless modem A modem that See also routing table. shifts all the protocol management, error de- tection and correction, and data compres- convergence sublayer Abbreviated CS. sion onto software running on the system’s One of two sublayers that make up the ATM CPU. This allows the modem manufacturer Adaptation Layer; the other being the seg- to make a much cheaper modem that does mentation and reassembly sublayer (SAR). not require the memory or processing power The convergence sublayer is the upper layer of a traditional modem. Also known as a soft that provides the interface for the various modem. ATM services, pads the cells, and adds control set That portion of the Micro- headers and trailers before passing the cell soft Windows Registry that contains infor- to the SAR. mation required to boot the operating sys- See also ATM Adaptation Layer; segmen- tem and restore the last known good tation and reassembly sublayer. configuration. conventional memory The amount of cookie 1. A block of data sent from a memory accessible by MS-DOS in PCs using server to a client in response to a request by an Intel processor operating in real mode; the client. normally the first 640KB. 2. On the World Wide Web, a block of data The designers of the original IBM PC made stored by the server on the system running 640KB available to the operating system the browser or client software, which can and applications and reserved the remain- be retrieved by the server during a future ing space for internal system use, the BIOS, session. A cookie contains information that and video buffers. Although 640KB may can identify the user for administrative rea- not seem like much memory space now, it sons or to prepare a custom Web page. was ten times the amount of memory avail- able in other leading personal computers cooperative multitasking A form of available at the time. Since then, applica- multitasking in which all running applica- tions have increased in size to the point that tions must work together to share system 640KB is inadequate. resources. 91 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 92 Thursday, May 4, 2000 11:59 AM Copper Distributed Data Interface The operating system supports cooperative must be distributed to others without multitasking by maintaining a list of the ac- charge. tive applications and the order in which they See also open source software. execute. When control is transferred to an application, the other applications cannot CORBA See Common Object Request run until that application returns control Broker Architecture. back to the operating system once again. COSE See Common Open Software A cooperative multitasking system differs Environment. from a preemptive multitasking system, in which the operating system executes each counter log In Microsoft Windows application in turn for a specific period of 2000, a System Monitor log used to moni- time (depending on priority) before switch- tor data from local or remote computers ing to the next application, regardless of about hardware use and system service ac- whether the applications themselves return tivity. control to the operating system. See also alert log; System Monitor; trace log. See also context switching; time-slice multitasking. Country object In Novell Directory Ser- vices, a container object placed directly un- Copper Distributed Data Interface der the Root object in the Directory tree Abbreviated CDDI. A version of the FDDI that defines the country for a specific part of standard designed to run on shielded and your network. Country object names are unshielded twisted-pair cable rather than defined by the International Organization on fiber-optic cable. CDDI is capable of for Standardization (ISO) and follow a 100Mbps data transfer rates. standard naming convention. You must See also Fiber Distributed Data Interface. specify the Country object if you want to connect to external networks using X.500 coprocessor A secondary processor directory services. used to speed up operations by taking over CPDA See Certified PowerBuilder De- a specific part of the main processor’s work. veloper Associate. The most common type of coprocessor is the math, or floating-point, coprocessor, CPDP See Certified PowerBuilder De- which is designed to manage arithmetic cal- veloper Professional. culations many times faster than does the CPE See customer-premises main processor. equipment. copy left The copyright or General Pub- CPI-C See Common Programming In- lic License of the Free Software Foundation terface for Communications. (FSF), which states that any of the software developed using free software from the FSF cps See characters per second. 92 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 93 Thursday, May 4, 2000 11:59 AM Ctrl+Alt+Del CPTS See Certified Performance and Windows NT 4 that provides encryption Tuning Specialist. and decryption functions for application developers. CPU See central processing unit. CS See convergence sublayer. cracker An unauthorized person who breaks into a computer system planning to CSE See Certified Solutions Expert. do harm or damage or with criminal intent. The popular press often portrays crackers C shell In Unix, a popular command in- as people with exceptional talent for elud- terpreter; pronounced “sea shell.” ing detection, and some of them are, but Developed at the University of California at most of them use a set of well-worn tricks to Berkeley as part of the BSD development as exploit common security weaknesses in the an alternative to the Bourne shell. In addi- systems they target. tion to the features found in the Bourne See also attack; hacker; intruder. shell, the C shell adds integer arithmetic, a history mechanism that can recall past com- crash An unexpected program halt, some- mands in whole or in part, aliasing of fre- times due to a hardware failure but most of- quently used commands, job control, and a ten due to a software error, from which there built-in set of operators based on the C pro- is no recovery. You usually need to reboot gramming language used for writing shell the computer to recover after a crash. scripts. See also blue screen of death. See also Bash; Bourne shell; Korn shell; Linux; Unix shell. CRC See cyclical redundancy check. CSMA/CD See Carrier Sense Multiple critical error An error in a program that Access/Collision Detection. forces the program to stop until the user corrects the error condition. Examples of CSRG See Computer Systems Re- this kind of error are attempts to write to a search Group. floppy disk when there is no disk in the drive or to print to a printer that has run out CSU See Channel Service Unit. of paper. Ctrl+Alt+Del A three-key combination crosstalk In communications, any inter- used to reset the machine and reload the op- ference from a physically adjacent channel erating system. By pressing Ctrl+Alt+Del, that corrupts the signal and causes trans- you initiate a warm boot, which restarts the mission errors. computer without going through the pow- er-on self tests (POSTs) normally run when See also far-end crosstalk; near-end the computer goes through a cold boot. crosstalk. In Windows 98 and 2000, the sequence Cryptography API Abbreviated CAPI. opens a dialog box from which you can An API first introduced in Microsoft either end a task or shut down the 93 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 94 Thursday, May 4, 2000 11:59 AM Ctrl+Break computer. Sometimes called the three- current drive In many operating sys- finger salute. tems, the disk drive that is being used for reading and writing files. The current drive See also warm boot. is not the same as the default drive, which is the drive that an application uses unless you Ctrl+Break See Ctrl+C. specify another. Ctrl+C 1. A key combination recognized See also drive mapping. by Unix, MS-DOS, and other operating sys- tems as a user-initiated interruption. Press- cursor A special character displayed on a ing Ctrl+C stops a batch file, macro, or monitor to indicate where the next charac- command (for example, a directory listing, ter will appear when it is typed. In text or a search, or a sort). character mode, the cursor is usually a blinking rectangle or underline. In a graph- 2. A keyboard shortcut recognized by ical user interface, the mouse cursor can many programs as the instruction to copy take many shapes, depending on the current the selected item. operation and its screen location. Ctrl key A key on the keyboard that, cursor-movement keys The keys on when pressed at the same time as another the keyboard that move the cursor; also key, generates a nonprinting control called cursor-control keys. These keys in- character. clude the four labeled with arrows and the On some keyboards, this key is labeled Home, Pg Up, End, and Pg Dn keys. Control rather than Ctrl, but it produces On full-size keyboards, cursor-movement the same function. keys are often found on the numeric key- pad; laptops and notebooks often have sep- CTS See Clear to Send. arate cursor-movement keys. CUE See Certified Unicenter Engineer. CU-SeeMe A popular videoconferencing current directory In many operating and videophone product that works over systems, the directory that will be searched the Internet. first for any file you request, and the direc- CU-SeeMe was originally developed at tory in which any new files will be stored Cornell University and is available free for (unless you specifically designate another the PC and the Macintosh. An enhanced directory). The current directory is not the commercial version that adds an electronic same as the default directory, which is the chalkboard is available from White Pine directory that an application uses unless Software. The software is designed for per- you specify another. sonal use and for use in instruction and in business communications. See also dot; dot dot; period and double- period directories. See also White Pine Software. 94 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 95 Thursday, May 4, 2000 11:59 AM Cyrix Customer Information Control cyclical redundancy check Abbreviat- System Abbreviated CICS. An IBM- ed CRC. A complex calculation method mainframe client/server program that man- used to check the accuracy of a digital trans- ages transaction processing in IBM’s VM mission over a communications link or to and MVS operating systems and that is scal- ensure the integrity of a file stored on a hard able to thousands of users. It also provides disk. password security, transaction logging for The sending computer uses one of several backup and recovery, and an activity log formulas to calculate a value from the that can be used to analyze session perfor- information contained in the data, and this mance, as well as facilities for creating, us- value is appended to the message block be- ing, and maintaining databases. fore it is sent. The receiving computer per- forms the same calculation on the same customer-premises equipment Ab- data and compares this number with the breviated CPE. Communications equip- received CRC. If the two CRCs do not ment, either leased or owned, used at a match, indicating a transmission error, the customer site. receiving computer asks the sending com- puter to retransmit the data. cut through A technique used by some This procedure is known as a redundancy Ethernet hardware to speed up packet for- check because each transmission includes warding. Only the first few bytes of the extra or redundant error-checking values as packet are examined before it is forwarded well as the data itself. or filtered. This process is much faster than looking at the whole packet, but it does al- As a security check, a CRC may be used to low some bad packets to be forwarded. compare the current size of an executable file against the original size to determine if See also store-and-forward. the file has been tampered with or changed in some way. cut-through switching A type of switch- See also checksum; Kermit; Xmodem; ing used on a Token Ring network in which Ymodem; Zmodem. data is forwarded as soon as the first 20 or 30 bytes in a data frame have been read. Cyrix A designer of microprocessors, in- After the header information has been read, cluding clones of popular Intel chips such as the connection is established between input the 6x86MX and the MII (pronounced M- and output ports, and the transmission be- two). Cyrix was bought by National Semi- gins immediately. Sometimes known as on- conductor in 1998. the-fly switching. For more information about Cyrix, see See also store-and-forward. www.cyrix.com. See also Advanced Micro Devices, Inc.; CxBus See Cisco Extended Bus. Pentium; Pentium II; Pentium III. 95 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 96 Thursday, May 4, 2000 11:59 AM DACL D DACL See Discretionary Access Control personal data on the space shuttle astro- List. nauts, or a collection of graphical images and video clips. daemon Pronounced “dee-mon.” A background program that runs unattended See also database management system; and is usually invisible to the user, provid- database model; table. ing important system services. Daemons manage all sorts of tasks, includ- database management system Ab- ing e-mail, networking, and Internet breviated DBMS. Software that controls services. Some daemons are triggered au- the data in a database, including overall or- tomatically by events to perform their ganization, storage, retrieval, security, and work; others operate at timed intervals. data integrity. A DBMS can also format re- Because daemons spend so much of their ports for printed output and can import and time idle, waiting for something to hap- export data from other applications using pen, they do not consume large amounts of standard file formats. A data-manipulation system resources. language is usually provided to support database queries. DAP See Directory Access Protocol. See also database; database model; query DAS See dual-attached station. language. DAT See digital audio tape. database model The method used by a data Information in a form suitable for database management system (DBMS) to processing by a computer, such as the digi- organize the structure of the database. The tal representation of text, numbers, graphic most common database model is the rela- images, or sounds. Strictly speaking, data is tional database. the plural of the Latin word datum, mean- See also relational database. ing an item of information; but the term is commonly used in both plural and singular database server Any database applica- constructions. tion that follows the client/server architec- database A collection of related objects, ture model, which divides the application including tables, forms, reports, queries, and into two parts: a front-end running on the scripts, created and organized by a database user’s workstation and a back-end running management system (DBMS). A database on a server or host computer. The front-end can contain information of almost any type, interacts with the user and collects and dis- such as a list of magazine subscribers, plays the data. The back-end performs all 96 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 97 Thursday, May 4, 2000 11:59 AM Data Encryption Standard the computer-intensive tasks, including to a communications channel or public net- data analysis, storage, and manipulation. work; usually a modem. See also data terminal equipment. Database Specialist: Informix Dynamic Server A certification from Informix de- data compression Any method of en- signed for computer professionals who im- coding data so that it occupies less space plement and manage Informix Dynamic than it did in its original form, thus allow- Server databases. The associated exams cov- ing that data to be stored, backed up, re- er relational database design, Structured trieved, or transmitted more efficiently. Query Language (SQL), and management and optimization of Informix Dynamic Serv- Data compression is used in fax and many er databases. other forms of data transmission, CD- ROM publishing, still-image and video-im- See also Informix-4GL Certified Profes- age manipulation, and database manage- sional; system administration. ment systems. See also Huffman coding; Joint Photo- data bits In asynchronous transmis- graphic Experts Group; lossless compres- sions, the bits that actually make up the da- sion; lossy compression; Moving Pictures ta. Usually, seven or eight data bits are Experts Group. grouped together. Each group of data bits in a transmission is preceded by a start bit data connector (Type 1) A connector and followed by an optional parity bit as for use with Type 1 cable, designed by IBM well as one or more stop bits. for use in Token Ring network wiring See also communications parameters; centers. parity; start bit; stop bit(s). data-encoding scheme The method used by a hard-disk controller to store infor- Data Carrier Detect Abbreviated DCD. mation onto a hard disk or a floppy disk. A hardware signal defined by the RS-232-C Common encoding schemes include the standard that indicates that the device, run-length limited (RLL) and advanced run- usually a modem, is online and ready for length limited (ARLL) methods. transmission. See also advanced run-length limited en- data communication The transfer of coding; RLL encoding. information from one computer to another over a communications link. The transfer Data Encryption Standard Abbreviat- can be occasional, continuous, or a combi- ed DES. A standard method of encrypting nation of both. and decrypting data, developed by the U.S. National Bureau of Standards. DES works data communications equipment by a combination of transposition and sub- Abbreviated DCE. In communications, any stitution. It is used by the federal govern- device that connects a computer or terminal ment and most banks and money-transfer 97 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 98 Thursday, May 4, 2000 11:59 AM data file systems to protect all sensitive computer control (LLC) layer sits above the media ac- information. cess control (MAC) layer. See also encryption; Pretty Good Privacy. See also OSI Reference Model. data file A file that contains informa- Data Link Switching Abbreviated tion—text, graphics, or numbers—rather DLSw. A standard for encapsulating or tun- than executable program code. neling IBM Systems Network Architecture (SNA) and NetBIOS applications across IP datagram A message unit that contains networks. source and destination address informa- See also Advanced Peer-to-Peer Network- tion, as well as the data itself, which is rout- ing; Systems Network Architecture. ed through a packet-switching network. The data held in the datagram is often re- data mining The process of displaying ferred to as the payload, and the addressing historical commercial data in a multidimen- information is usually contained in the sional form so that previously hidden rela- header. Because the destination address is tionships are exposed through the use of contained in all datagrams, they do not advanced statistical tools, making them have to arrive in consecutive order. Data- easier to group and summarize. grams are commonly used in connectionless See also data warehousing; online ana- transmission systems. IP (Internet Protocol) lytical processing; online transaction and IPX (Internetwork Packet Exchange) processing. are both datagram services. data packet One unit of information See also frame; data packet. transmitted as a discrete entity from one node on the network to another. More spe- Datagram Delivery Protocol Abbrevi- cifically, a packet is a transmission unit of a ated DDP. A routing protocol developed by fixed maximum length that contains a Apple Computer as a part of its AppleTalk header with the destination address, a set of network. data, and error control information. data-link layer The second of seven lay- See also frame. ers of the OSI Reference Model for comput- er-to-computer communications. The data- data processing Abbreviated DP. Also link layer validates the integrity of the flow called electronic data processing (EDP). A of data from one node to another by syn- term used to describe work done by mini- chronizing blocks of data and controlling computers and mainframe computers in a the flow of data. data center or business environment. The Institute of Electrical and Electronic data protection Techniques used by Engineers (IEEE) has divided the data-link network operating systems to ensure the in- layer into two other layers—the logical link tegrity of data on the network, including 98 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 99 Thursday, May 4, 2000 11:59 AM DB connector protecting data against surface defects de- data-transfer rate 1. The speed at veloping on the disk and storing redundant which a disk drive can transfer information copies of important system data, such as file from the drive to the processor, usually mea- indices and file allocation tables (FATs). sured in megabits or megabytes per second. Disk duplexing, disk mirroring, a well 2. The rate of information exchange be- thought out backup scheme, and RAID tween two systems. For example, an Ether- techniques all provide different levels of net LAN may achieve 10Mbps, and a Fiber data protection. Distributed Data Interface (FDDI) system See also diskless workstation; disk strip- may reach 100Mbps. ing; disk striping with parity; fault toler- ance; Hot Fix; intruder; redundant array of See also connection speed. inexpensive disks; virus. data warehousing A method of storing Data Service Unit Abbreviated DSU. A very large amounts of data, usually histor- device that connects DTE (data terminal ical transaction processing data, for later equipment) to digital communications analysis and reporting. lines. A DSU formats the data for transmis- The data warehouse is accessed by software sion on the public carrier WANs and en- capable of extracting trends from the raw sures that the carrier’s requirements for data and creating comparative reports. data formats are met. See also data mining. See also Channel Service Unit. Data Set Ready Abbreviated DSR. A dB See decibel. hardware signal defined by the RS-232-C standard to indicate that the device is ready DB connector Any of several types of ca- to operate. ble connectors used for parallel or serial ca- bles. The number following the letters DB See also Clear to Send. (for data bus) indicates the number of pins that the connector usually has; a DB-25 data terminal equipment Abbreviated connector can have a maximum of 25 pins, DTE. In communications, any device, such and a DB-9 connector can have as many as as a terminal or a computer, connected to a 9. In practice, not all the pins (and not all communications device, channel, or public the lines in the cable) may be present in the network. larger connectors. If your situation de- See also data communications equipment. mands that all the lines be present, make sure you buy the right cable. Common DB Data Terminal Ready Abbreviated connectors include the following: DTR. A hardware signal defined by the RS-232-C standard sent from a computer I DB-9 Defined by the RS-449 standard to a modem to indicate that the computer as well as the ISO (International Organi- is ready to receive a transmission. zation for Standardization). 99 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 100 Thursday, May 4, 2000 11:59 AM DBCS I DB-25 A standard connector used with DB-15, DB-19, and DB-50 connectors are RS-232-C wiring, with 25 pins (13 on the also available. The accompanying illustra- top row and 12 on the bottom). tion shows a male and female DB-25 I DB-37 Defined as the RS-449 primary connector. channel connector. DB CONNECTOR DBCS See double-byte character set. In the Base Rate ISDN (BRI), the D channel operates at 16Kbps; in the Primary Rate DBMS See database management ISDN (PRI), it operates at 64Kbps. system. DCOM See Distributed Component DC-2000 A quarter-inch tape minicartridge Object Model. used in some tape backup systems. DC-2000 has a capacity of up to 250MB when some DCPROMO In Microsoft Windows 2000 form of data compression is used. Server, the Active Directory Installation See also quarter-inch cartridge. Wizard that promotes a member server or stand-alone server to a domain controller. DCD See Data Carrier Detect. When run on a domain controller, this pro- gram can demote the computer to a mem- DCE See data communications ber server or a stand-alone server. equipment. DDCMP See Digital Data Communica- DCE See Distributed Computing tions Message Protocol. Environment. DDD See direct distance dialing. D channel The channel in ISDN that is used for control signals and customer data. DDE See Dynamic Data Exchange. 100 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 101 Thursday, May 4, 2000 11:59 AM dedicated circuit DDNS See Dynamic DNS. See also encapsulation. DDP See Datagram Delivery Protocol. decibel Abbreviated dB. One-tenth of a bel, a unit of measurement common in elec- deadlock An error condition or stale- tronics that quantifies the loudness or mate that occurs when two programs or de- strength of a signal. A decibel is a relative vices are each waiting for a signal from the measurement derived by comparing a mea- other before they can continue. sured level against a known reference. DEC See Digital Equipment Corporation. decimal The base-10 numbering system that uses the familiar numbers 0–9; also DEC Alpha Also called the DEC Alpha known as the base 10 radix or the decimal AXP or the DECchip 21264. A 64-bit, radix. RISC (reduced instruction set computing) microprocessor from Digital Equipment See also binary; hexadecimal. Corporation (DEC), first introduced in decimal radix See decimal. 1992. The Alpha is a superscalar, superpipelined DECnet A series of communications and design, which allows the processor to exe- networking products from Digital Equip- cute more than one instruction per clock ment Corporation (DEC). DECnet is com- cycle; it can execute as many as six instruc- patible with Ethernet, as well as with tions per clock cycle and can sustain four WANs using baseband and broadband pri- instructions per clock cycle. vate and public communications channels. DECnet is built into the VAX VMS operat- It has data and instruction caches, a float- ing system. ing-point processor, 64-bit registers, 64-bit See also Digital Network Architecture. data and address buses, and a 128-bit data path between the processor and memory. decode 1. To decompress a video file af- The internal architecture is symmetrical ter receipt so that you can view it. Most de- multiprocessing (SMP) compliant, meaning coding is done by the client browser. that it can be used in multiprocessing con- 2. To convert coded data back into its orig- figurations. The chip is available in several inal form, usually as readable text. models with operating frequencies in the 300 to 700MHz range; a 1GHz model is ex- See also codec; decryption; encode; pected by the year 2000. uuencode. decapsulation A process used in net- decryption The process of converting working in which the receiving system encrypted data back into its original form. looks at the header of an arriving message See also encryption. to determine if the message contains data. If the message does contain data, the header is dedicated circuit See dedicated line; removed and the data decoded. direct connection. 101 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 102 Thursday, May 4, 2000 11:59 AM dedicated line dedicated line A communications cir- Some operating systems create several de- cuit used for one specific purpose and not fault directories when the file system is cre- used by or shared between other users. You ated. For example, Novell NetWare creates need only dial a dedicated line to restore the following directories when the SYS vol- service after an unscheduled interruption. ume is created: Also known as a dedicated circuit. I SYS:SYSTEM, for the NetWare operating See also leased line. system files dedicated router A router that performs I SYS:PUBLIC, for utility and user programs no functions other than routing tasks. I SYS:LOGIN, for programs allowing users to log in to the server dedicated server A computer on the network that functions only as a server per- I SYS:MAIL, a directory used by NetWare- forming specific networking tasks, such as compatible electronic-mail applications storing files, printing, or managing external default server In Novell NetWare, the communications. server that responds to the Get Nearest Dedicated Token Ring An IEEE 802.5r Server request made as a user starts the Token Ring specification that allows for logon process. Novell Directory Services full-duplex connections at a speed of up to has replaced the need for the default server 32Mbps. By enabling full-duplex commu- destination with the default context. nications, the token-passing mechanism is See also Context. not used, and communications can take place between a device and a switch at any default shares In Microsoft Windows time. 2000, resources shared by default when the See also 802.x; token-ring network. operating system is first installed. See also common share; hidden share; default A standard setting, used until an share; sharing. alternative is chosen. The default server is the first server that you log on to. The de- defense in depth A term borrowed fault drive is the drive that a workstation is from the military used to describe defensive currently using. measures that reinforce each other, hiding A default is usually a relatively safe course the defenders activities from view and al- of action to try first; many programs pro- lowing the defender to respond to an attack vide defaults you can use until you know quickly and effectively. enough about the program to specify your In the network world, defense in depth de- own settings. scribes an approach to network security default directory A standard directory that uses several forms of defense against an or set of directories used by the operating intruder and that does not rely on one single system or by an application. defensive mechanism. 102 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 103 Thursday, May 4, 2000 11:59 AM demand paging defragmentation The process of reorga- hidden, it is still there on the disk until it is nizing and rewriting files so that they occu- overwritten. In certain circumstances it is py one large area on a hard disk rather than possible to undelete or recover the original several smaller areas. information with utilities designed for that When a file on a hard disk is updated, it may purpose. If you find you have deleted an be written into different areas all over the important file by accident, do not write disk. This outcome is particularly likely any other files to that disk so that you do when the hard disk is continuously updated not overwrite the deleted file. Some net- over a long period of time. This file frag- work operating systems use a delete inhibit mentation can lead to significant delays in attribute to prevent accidental deletions; loading files, but its effect can be reversed other operating systems rely on a read- by defragmentation. only attribute. See also disk optimizer. delimiter 1. Any special character that separates individual items in a data set or defragmenter Any utility that rewrites file. For example, in a comma-delimited all the parts of a fragmented file into contig- file, the comma is placed between each data uous areas on a hard disk. A defragmenter value as the delimiter. (such as the Microsoft Windows 98 utility Disk Defragmenter) can restore perfor- 2. In a token-ring network, a delimiter is a mance lost because of file fragmentation. bit pattern that defines the limits of a frame See also defragmentation; disk optimizer. or token on the network. delay In communications, a pause in ac- Dell Computer Corporation One of the tivity, representing the time during which world’s top five PC manufacturers. Dell pi- transmission-related resources are unavail- oneered direct sales of the PC using a con- able for relaying a message. figure-it-yourself Web site. See also propagation delay. Best known for PC and laptop sales, Dell is also pursuing the server market and has re- delay distortion The distortion of a sig- cently expanded into the enterprise storage nal caused by the relative difference in market with the PowerVault line of SCSI- speed of the various components of that sig- based storage subsystems, tape backup sys- nal; in particular, the distortion of the high- tems, and scalable disk subsystems. frequency component. Also called envelope For more information on Dell, see delay. www.dell.com. delete To remove a file from a disk or to remove an item from a file. Files can be de- demand paging A common form of vir- leted using operating system commands or tual memory management in which pages directly from within an application. of information are read into memory from disk only when required by the program. When a file is deleted from a disk, the file is not physically removed; although it is See also swapping. 103 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 104 Thursday, May 4, 2000 11:59 AM demand priority demand priority A technique used in people working on common tasks; it pro- 100VG-AnyLAN to arbitrate access to the vides shared local resources, such as print- network and avoid collisions. Demand pri- ers, data, and applications. ority replaces CSMA/CD, which is used in DES See Data Encryption Standard. slower Ethernet networks. Demand priority can also prioritize specific descendant key In Microsoft Windows, network traffic such as video and other all the subkeys that appear when you ex- time-critical data, giving it a higher prece- pand a key in the Windows Registry. dence; if multiple requests are received, the See also key; Registry. highest priority is always serviced first. See also Fast Ethernet. DeskSet A collection of graphical desk- top applications bundled with Sun Micro- demodulation In communications, the system’s Solaris. process of retrieving the data from a DeskSet includes a file manager with op- modulated carrier signal; the reverse of tions for copying, moving, renaming, and modulation. deleting files, a terminal emulator, text ed- See also modem. itor, calculator, clock, and calendar, as well as special programs and utilities. denial of service attack An attack by See also Solaris. an intruder that prevents a computer sys- tem from providing a service. desktop management The process of A denial-of-service attack will typically in- managing desktop workstation hardware volve opening and dropping a large number and software components automatically, of TCP/IP connections very quickly so that often from a central location. the target system spends all its time dealing See also total cost of ownership; Zero Ad- with the connection overhead to the point ministration for Windows. that it cannot respond to valid user re- quests. Other attacks may exploit known Desktop Management Interface Ab- software security holes to crash servers. breviated DMI. A standard API for identify- A denial-of-service attack is much easier to ing desktop workstation hardware compo- execute than an attempt at unauthorized nents automatically, without intervention access, because the denial-of-service attack from the user. never actually requires access to the system. At a minimum, DMI identifies the manu- See also brute-force attack; dictionary at- facturer, component name, version, serial tack; mail bombing; social engineering; number (if appropriate), and installation Trojan Horse. time and date of any component installed in a networked workstation. This information departmental LAN A local-area net- is designed to help network administrators work used by a relatively small group of resolve configuration problems quickly and 104 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 105 Thursday, May 4, 2000 11:59 AM device name easily and to indicate when and where sys- your terminal, it is actually writing to a spe- tem upgrades should be applied. PCs, Mac- cial file that represents your terminal. intosh computers, and Unix systems are all See also device driver. covered by DMI. DMI is backed by Digital Equipment Cor- device dependence The requirement poration (DEC), IBM, Intel, Microsoft, No- that a specific hardware component be vell, Sun, and more than 300 other vendors. present for a program to work. Device-de- pendent software is often difficult to move See also Plug and Play; total cost of own- or port to another computer because of its ership; Web-based Enterprise Manage- reliance on specific hardware. ment; Wired for Management; Zero See also device independence. Administration for Windows. device driver A small program that al- desktop video The combination of vid- lows a computer to communicate with and eo capture hardware and application soft- control a device. Each operating system con- ware that controls the display of video or tains a standard set of device drivers for the television pictures on a desktop PC. keyboard, the monitor, and so on. When you Desktop video is becoming increasingly im- add specialized peripheral devices, such as a portant with the sharp increase in video- CD-ROM disk drive or a network interface conferencing applications now available. card, you must install the appropriate device driver so that the operating system knows destination address The address por- how to manage the device. tion of a packet or datagram that identifies See also Plug and Play. the intended recipient station. See also source address. device independence The ability to produce similar results in a variety of envi- destination host A computer system on ronments, without requiring the presence the network that is the final destination for of specific hardware. a file transfer or for an e-mail message. The Java programming language and the device A general term used to describe PostScript page-description language are any computer peripheral or hardware ele- examples of device independence. Java runs ment that can send or receive data. on a wide range of computers, from the PC to a Cray; PostScript is used by many print- Some examples are modems, printers, serial er manufacturers. ports, disk drives, routers, bridges, and con- See also device dependence. centrators. Some devices require special soft- ware, or device drivers, to control or manage device name The name used by the them; others have built-in intelligence. operating system to identify a computer- In Unix and certain other operating systems, system component. For example, COM1 is all peripherals are treated as though they the Windows device name for the first were files. When Unix writes information to serial port on the PC. 105 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 106 Thursday, May 4, 2000 11:59 AM device number device number A unique number as- dial-in/dial-out server See asynchro- signed to a device so that it can operate on nous communications server. the network. Devices are identified by three numbers: Dialogic Corp A major manufacturer of high-performance telephony products, in- I A physical address set by jumpers on the cluding those used in voice, data, fax, adapter board speech synthesis, ISDN networking, and I A device code determined by the physical call center management applications. address For more information on Dialogic, see I A logical address determined by the order www.dialogic.com. in which the drivers are loaded and by the dialup line A nondedicated communica- physical address of the adapter tion line in which a connection is estab- See also Ethernet address; hardware lished by dialing the destination code and address. then broken when the call is complete. See also dedicated line; leased line. Dfs See Distributed file system. Dial-Up Networking Software provided DHCP See Dynamic Host Configuration with Microsoft’s Windows products that Protocol. allows the clients to dial out and establish diagnostic program A program that Point-to-Point Protocol (PPP) connections. tests computer hardware and peripheral de- dictionary attack An attack by an in- vices for correct operation. Some faults, truder that checks passwords in a password known as hard faults, are relatively easy to file against a list of words likely to be used find, and the diagnostic program will diag- as passwords. Some versions of this attack nose them correctly every time. Other check the entire language lexicon. faults, called soft faults, can be difficult to find, because they occur under specific cir- See also brute-force attack; denial of ser- cumstances rather than every time the vice attack; mail bombing; social engineer- memory location is tested. ing; Trojan Horse. Most computers run a simple set of system differential backup A backup of a hard checks when the computer is first turned disk that includes only the information that on. The PC tests are stored in ROM and are has changed since the last complete backup. known as power-on self tests (POSTs). If a POST detects an error condition, the com- A differential backup assumes that a full puter stops and displays an error message backup already exists and that in the event on the screen. of an accident, this complete backup will be restored before the differential backup dialback modem See callback modem. is reloaded. 106 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 107 Thursday, May 4, 2000 11:59 AM digital signal differential SCSI A Small Computer Digital Equipment Corporation Ab- System Interface (SCSI) bus wiring scheme breviated DEC. A major manufacturer of that uses two wires for each signal on the minicomputers and mainframe computers, bus. One wire carries the signal, while the founded in 1957, long recognized for its other carries its inverse. Differential SCSI high-quality computer systems. DEC’s minimizes the effects of external interfer- most popular product line, the VAX series, ence and so allows longer SCSI cable ranges from small desktop systems to large lengths to be used. mainframes suitable for scientific and com- See also single-ended SCSI; Small Com- mercial processing. DEC was bought by puter System Interface. Compaq Computer Corporation in 1998. For more information on DEC, see digest A collection of Internet mailing www.digital.com. list posts collected together and sent out as See also DEC Alpha. a single large message rather than as a num- ber of smaller messages. Using a digest is a Digital Network Architecture Abbre- good way to cut down on the number of viated DNA. The framework within which noncritical e-mail messages you receive. Digital Equipment Corporation (DEC) de- See also LISTSERV; listserver; mailing list. signs and develops all its communications products. digital Describes any device that repre- digital service See digital signal. sents values in the form of binary digits or bits. digital signal Abbreviated DS; also See also analog. known as digital service. There are several levels of common carrier digital transmis- digital audio tape Abbreviated DAT. A sion service: method of recording information in digital I DS-0 64Kbps. form on a small audio tape cassette, origi- I DS-1 1.544Mbps (T1). nally developed by Sony and Hewlett-Pack- ard. The most common format is a 4- I DS-1C Two DS-1 channels are multi- millimeter, helical-scan drive, which can plexed into a single DS-1C 3.152Mbps hold more than 3GB of information. DATs channel. can be used as backup media; however, like I DS-2 Two DS-1C channels are multi- all tape devices, they are relatively slow. plexed into one DS-2 6.312Mbps (T2) channel. Digital Data Communications Mes- sage Protocol Abbreviated DDCMP. A I DS-3 Seven DS-2 channels are multi- byte-oriented, link-layer synchronous pro- plexed into a single 44.736Mbps (T3) tocol from Digital Equipment Corporation channel. (DEC), used as the primary data-link com- I DS-4 Six DS-3 channels are multiplexed ponent of DECnet. into one 274.176Mbps (T4) DS-4 channel. 107 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 108 Thursday, May 4, 2000 11:59 AM Digital Signal Processing The higher-capacity channels are construct- DS-0 is also referred to as fractional T1, ed by multiplexing the lower-bandwidth because it bridges the gap between 56-Kbps channels together, with some additional direct dial service (DDS) and a full T1 framing and administrative overhead. implementation. DIGITAL SIGNAL Digital Signal Processing Abbreviated digital signature An electronic signa- DSP. An integrated circuit used in high- ture that cannot be forged. A digital signa- speed data manipulation. You will find DSP ture confirms that the document or e-mail chips integrated into sound cards, modems, in question originated from the individual and video-conferencing hardware for use in or company whose name appears on the communications, image manipulation, and document and that the document has not other data-acquisition applications. been altered or tampered with in any way See also codec; desktop video. since it was signed. See also certificate. 108 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 109 Thursday, May 4, 2000 11:59 AM DIP switch Digital Subscriber Line Abbreviated per disc. DVD drives can also read conven- DSL. A high-speed data transmission tech- tional compact discs. nology originally developed by Bellcore digital video disc-erasable Abbreviat- that delivers high bandwidth over existing ed DVD-E. An extension to the digital video twisted-pair copper telephone lines. disc format to allow multiple re-recordings. There are several DSL services, providing See also digital video disc-recordable. data rates from 16Kbps to 52Mbps. The services can be symmetrical, with the same digital video disc-recordable Abbrevi- data rate in both upstream and downstream ated DVD-R. An extension to the digital vid- directions, or asymmetrical, with the down- eo disc format to allow one-time recording. stream capacity greater than the upstream See also digital video disc-erasable. capacity. Asymmetric services are particu- larly suitable for Internet users, because digital video disc-ROM Abbreviated more information is downloaded than is DVD-ROM. A computer-readable form of uploaded. digital video disc with either 4.7 or 8.5GB As DSL data rates increase, the distance of storage per side. over which the service is provided decreas- dimmed command In a graphical user es; certain users who are located too far interface, a command that is not currently from the telephone company’s central of- available. Also known as a grayed com- fice may not be able to obtain the higher mand, because it is often displayed in light speeds or, in some cases, may not be able to gray rather than the usual black. For exam- receive the service at all. ple, a command to perform a network ac- See also Asymmetric Digital Subscriber tion will be dimmed until you log on to the Line; High-Bit-Rate Digital Subscriber Line; network. Rate-Adaptive Digital Subscriber Line; DIN connector A connector that meets Single-Line Digital Subscriber Line; Very- the specification of the German national High-Bit-Rate Digital Subscriber Line. standards body, Deutsche Industrie Norm (DIN). digital versatile disc See digital video disc. Several models of Macintosh computers use 8-pin DIN connectors as the serial port con- digital video disc Abbreviated DVD; nector. On many IBM-compatible comput- sometimes called digital versatile disc. A ers, a 5-pin DIN connector connects the compact disc format. A standard single-lay- keyboard to the system unit. er single-sided disc can currently store DIP See dual in-line package. 4.7GB of information; a two-layer standard increases this to 8.5GB, and eventually dou- DIP switch A small switch used to select ble-sided discs are expected to store 17GB the operating mode of a device, mounted 109 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 110 Thursday, May 4, 2000 11:59 AM direct access as a dual in-line package. DIP switches can They are used in printed circuit boards, be either sliding or rocker switches, and dot-matrix printers, modems, and many they are often grouped for convenience. other peripheral devices. DIP SWITCH direct access See random access. direct line See direct connection. direct connection A communications direct manipulation In a graphical user circuit used for one specific purpose and not interface, the process of working with ob- used by or shared with other users. Also jects using a mouse or other pointing device, known as a dedicated circuit or a direct line. rather than using menu selections to manip- An ISDN qualifies as a direct connection. ulate the objects. Using drag-and-drop to print a file or using the mouse to adjust the See also Integrated Services Digital size of a window are both examples of direct Network. manipulation. direct distance dialing Abbreviated direct memory access Abbreviated DDD. Use of the normal long-distance tele- DMA. A method of transferring informa- phone system without the need for the in- tion directly from a mass-storage device, tervention of an operator. such as a hard disk, into memory without the information passing through the pro- direct distance dial network See pub- cessor. Because the processor is not in- lic network. volved in the transfer, DMA is usually fast. 110 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 111 Thursday, May 4, 2000 11:59 AM Directory replica Directory 1. In Novell Directory Servic- directory caching A feature of Novell es (NDS), the Directory database contains NetWare that copies the file allocation and organizes all the NDS objects. table (FAT) and the directory entry table 2. In the Microsoft Active Directory struc- into the network server’s memory. When ture, a Directory contains information file requests are made, information is about users, groups of users, computers, retrieved from the cache rather than from and so on. the hard disk, thus speeding the retrieval process significantly. As the directory cache See also Active Directory; Directory ob- fills up, the least-used directory entries are ject; Directory Schema; directory tree; eliminated from the cache. Novell Directory Services. directory hashing A feature of Novell directory In a hierarchical file system, a NetWare that indexes file locations on disk, convenient way of organizing and grouping thus speeding file retrieval. files and other directories on a disk. Some- times called a folder. The beginning direc- Directory Map object In Novell Direc- tory is known as the root directory, from tory Services (NDS), a leaf object that refers which all other directories must branch. to a directory on a volume. The Directory Map object allows a drive to be mapped to Directories inside another directory are an application or to a login script without re- called subdirectories. quiring the actual path and volume where Depending on the operating system, you the application is physically located. This is can list the files in a directory in a variety of done so that login scripts don’t have to be re- ways: by name, by creation date and time, written when a drive path changes; you can by file size, or by icon if you use a graphical simply change the Directory Map object. user interface. See also Novell Directory Services. See also current directory; default directory; directory services; file allocation table; par- Directory object In Novell Directory ent directory; period and double-period Services (NDS), a set of properties stored in directories. the Directory database. A Directory object can represent a physical or a logical net- Directory Access Protocol Abbreviat- work resource, but it does not actually con- ed DAP. A mail standard used to access tain the resource. white page directories containing names, addresses, e-mail addresses, and telephone See also Directory; Novell Directory numbers. Because of its complexity, DAP Services. has been largely replaced by Lightweight directory path See path. Directory Access Protocol (LDAP). See also Lightweight Directory Access Directory replica In Novell NetWare, a Protocol. copy of the NetWare Directory partition 111 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 112 Thursday, May 4, 2000 11:59 AM directory replication that allows the NetWare Directory Data- directory service client Abbreviated base to be stored on several servers on the DSCLIENT. In Microsoft Windows 95/98, network without having to duplicate the an add-on that makes a Windows 95/98 cli- entire database on each server. Directory ent computer aware of Active Directory. replicas remove a single point of failure See also Active Directory. from the network and thereby increase fault tolerance. Directory Service log In Microsoft See also NetWare Directory Database. Windows 2000 Server, a special log that records any events associated with running the Directory Service, any problems con- directory replication A process that necting to the global catalog, and any copies a master set of directories from a events associated with Active Directory server, called an export server, to other (AD) on the network. specified servers or workstations, known as import computers. This process simplifies See also DNS Server log; Event Viewer; the task of maintaining and synchronizing File Replication Service log. identical sets of directories and files, be- cause only one master copy of the data is Directory services In the Microsoft Ac- maintained. A file is replicated when it is tive Directory structure, a directory as well added to an exported directory, as well as as the services it provides, such as security when changes are made to the file. and replication. See also Active Directory. Directory Schema In Novell Directory Services (NDS), a set of rules that defines directory services A listing of all users how information can be stored in the Direc- and resources on a network, designed to help tory database. The Schema contains four clients locate network users and services. major definitions: Some examples are the OSI’s X.500, Novell Directory Services (NDS), Microsoft’s Ac- I Attribute information Describes the tive Directory, and Banyan’s StreetTalk. kinds of information that can be associat- ed with an object. See also domain directory services; global directory services. I Inheritance Defines which objects can inherit the rights and properties of other directory structure duplication A objects. technique that maintains duplicate copies I Naming Determines the structure of the of the file allocation table (FAT) and direc- Directory tree. tory entry table in separate areas of a hard disk. If the first copy is damaged or de- I Subordination Specifies the location of stroyed, the second copy is immediately objects in the Directory tree. available for use. See also Novell Directory Services. See also directory verification. 112 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 113 Thursday, May 4, 2000 11:59 AM disk cache directory tree A method of representing See also backup; disk duplexing; disk mir- the hierarchical structure of the directories, roring; redundant array of inexpensive subdirectories, and files on a disk. The term disks. is often used in graphical user interfaces. In object-oriented systems, this structure may Discretionary Access Control List Ab- also represent a group of objects, as in No- breviated DACL. In Microsoft Windows vell Directory Services (NDS). NT, a list of user and group accounts that have permission to access an object’s ser- directory verification A process that vices. The DACL has as many Access Con- performs a consistency check on duplicate trol Entries as there are user or group sets of file allocation tables (FATs) and di- accounts with access to the object. rectory entry tables to verify that they are identical. The verification occurs every time disk cache Pronounced “disk cash.” An the server is started. area of computer memory where data is tem- See also directory structure duplication. porarily stored on its way to or from a disk. When an application asks for information disable To turn a function off or prevent from the hard disk, the cache program first something from happening. In a graphical checks to see if that data is already in the user interface, disabled menu commands cache memory. If it is, the disk cache pro- are often shown in gray to indicate that they gram loads the information from the cache are not available. memory rather than from the hard disk. If See also dimmed command; enable. the information is not in memory, the cache program reads the data from the disk, cop- disaster recovery The process used to ies it into the cache memory for future ref- restore services after a major interruption in erence, and then passes the data to the computing or in communications. Large requesting application. This process is events such as earthquakes or fires can inter- shown in the accompanying illustration. rupt networked computing activities, but so can more mundane events such as hard-disk A disk cache program can significantly speed failure or a construction worker accidentally most disk operations. Some network operat- cutting through a power or telephone line. ing systems also cache other often accessed The whole point to disaster recovery is to and important information, such as directo- plan for it before anything happens and then ries and the file allocation table (FAT). follow the plan when restoring services. See also directory caching. 113 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 114 Thursday, May 4, 2000 11:59 AM disk controller DISK CACHE disk controller The electronic circuitry Several types of disk drives are in common that controls and manages the operation of use: floppy disk drives, hard disk drives, floppy disks and hard disks. compact disc drives, digital video disc drives, A single disk controller may manage more Zip drives, and magneto-optical disc drives. than one hard disk. Many disk controllers disk duplexing A fault-tolerant tech- also manage floppy disks and compatible nique that writes the same information si- tape drives. In the Macintosh, the disk con- multaneously onto two hard disks. troller is built into the system. In the PC, the disk controller may be a printed circuit Each hard disk uses a different disk control- board inserted into the expansion bus, or it ler to provide greater redundancy. If one may be part of the hard disk drive itself. disk or disk controller fails, information from the other system can be used to con- disk coprocessor board See host bus tinue operations. Disk duplexing is offered adapter. by most major network operating systems. disk drive A peripheral storage device It is designed to protect the system against that reads and writes magnetic or optical a single disk failure, not multiple disk fail- disks. When more than one disk drive is in- ures. Disk duplexing is no substitute for a stalled on a computer, the operating system well-planned series of disk backups. assigns each drive (or logical drive) a unique See also data protection; disk mirroring; name. redundant array of inexpensive disks. 114 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 115 Thursday, May 4, 2000 11:59 AM disk striping with parity Disk Manager In Microsoft Windows disk optimizer A utility that rearranges 2000, the administrative tool used to man- files and directories on a disk for optimum age hard disks and other storage media. performance. By reducing or eliminating Disk Manager replaces NT’s Disk Admin- file fragmentation (storage in pieces in dif- istrator. ferent locations on the hard disk), a disk See also basic disk; dynamic disk. optimizer can restore the original level of performance of your disk system. Also, it is disk quotas In Microsoft Windows usually easier to undelete, or recover, an 2000, a feature that allows an administra- unfragmented file than a fragmented one. tor to limit the amount of hard disk space Many disk optimizers will not only rewrite available to a user. You can set quotas only files as contiguous files, but will also place on NTFS hard disks. specific unchanging files in particular loca- diskless workstation A networked tions on the disk, optimize directories, and computer that does not have any local disk even place specific applications on the disk storage capability. The computer boots and so that they load more quickly. loads all its programs from the network file See also defragmentation. server. Diskless workstations are particu- larly valuable when sensitive information is disk striping The technique of combin- processed; information cannot be copied ing a set of disk partitions located on differ- from the file server onto a local disk, be- ent hard disks into a single volume, creating cause the workstation does not have one. a virtual “stripe” across the partitions that See also dumb terminal; network com- the operating system recognizes as a single puter; thin client. drive. Disk striping can occur at the bit level or at the sector level and allows multiple disk mirroring A fault-tolerant tech- concurrent disk accesses that can improve nique that writes the same information si- performance considerably. multaneously onto two hard disks or two hard-disk partitions, using the same disk See also disk striping with parity; redun- controller. If one disk or partition fails, in- dant array of inexpensive disks; stripe set. formation from the other can be used to continue operations. Disk mirroring is of- disk striping with parity The addition fered by most major network operating sys- of parity information across a disk stripe so tems. It is designed to protect the system that if a single disk partition fails, the data against a single disk failure, not multiple on that disk can be re-created from the in- disk failures. Disk mirroring is no substitute formation stored across the remaining par- for a well-planned series of disk backups. titions in the disk stripe. See also data protection; disk duplexing; See also disk striping; redundant array of redundant array of inexpensive disks. inexpensive disks; stripe set. 115 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 116 Thursday, May 4, 2000 11:59 AM dispersion DISK STRIPING dispersion The degree of scattering that See also Common name; Context; Relative takes place as a beam of light travels along Distinguished Name. a fiber-optic cable. Distributed Component Object Model See also cladding. Abbreviated DCOM. A specification from Microsoft that enables communications be- distance vector algorithm A family of tween distributed objects. routing algorithms that calculate the best- DCOM extends the Component Object path route to use for data transmission Model (COM) so that clients can commu- from information present in adjacent nodes nicate directly with other processes on dif- on the network. Routing information is ferent computers on a LAN or on the broadcast periodically rather than only Internet. when a change occurs, which makes the See also ActiveX; Component Object method bandwidth intensive. For this rea- Model. son, distance vector algorithm is best used in relatively small networks with few inter- distributed computing See distributed router connections. processing. Distinguished Name In Novell Directo- Distributed Computing Environment ry Services (NDS), the full name of an ob- Abbreviated DCE. The Open Software ject, including the object’s Common name Foundation’s (OSF) architecture for devel- and its context. Sometimes called the Full oping application software for use on dif- Distinguished Name. ferent networks. 116 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 117 Thursday, May 4, 2000 11:59 AM DIX connector DCE hides the differences between products, Distributed System Object Model technologies, and standards, providing inde- Abbreviated DSOM. IBM’s extension to pendence from the operating system and un- System Object Model (SOM) that allows derlying network. No particular communi- objects to communicate in a distributed cations protocol is specified, so the network processing environment. can run on IP (Internet Protocol), IPX (Inter- distributed processing A computer network Packet Exchange), or SNA (Sys- system in which processing is performed by tems Network Architecture). several separate computers linked by a communications network. distributed database A database man- The term often refers to any computer sys- aged as a single system even though it in- tem supported by a network, but more cludes many clients and many servers at properly refers to a system in which each both local and remote sites. A distributed computer is chosen to handle a specific database requires that data redundancy is workload and the network supports the managed and controlled. system as a whole. Each computer contrib- utes to the completion of a common task by Distributed Director Web site load-bal- completing one or more subtasks indepen- ancing software from Cisco Systems. dently of its peers and then reporting the re- A popular Web site can be overwhelmed by sults from these subtasks. All this is totally requests from users, and to avoid long wait transparent to the users; all they see are the times, you can configure additional Web results of the process. servers to hold duplicate information. Web See also client/server architecture. requests are then sent to the Web server best distribution groups In Microsoft Win- able to handle the request. Distributed Di- dows 2000 Server, a collection of recipient rector runs on Cisco routers and uses a e-mail addresses. Distribution groups have routing protocol to send user requests to the nothing to do with system security. They do server that is closest to them. not have security identifiers, and they do not appear on access control lists. Distributed file system Abbreviated Dfs. In Microsoft Windows 2000 Server, a See also security groups. hierarchical file system that combines re- distribution medium The type of data- sources from all over the network into a sin- storage device used to distribute original gle logical view. software or software updates. distributed file system Any file system Tapes used to be the favorite distribution in which files and programs are located on medium, but compact discs are rapidly more than one computer or server. Users gaining popularity. can access files and applications as though DIX connector See Attachment Unit they were stored on a single local system. Interface. 117 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 118 Thursday, May 4, 2000 11:59 AM DLL DLL See Dynamic Link Library. systems that give you access to network connections, CD-ROMs, and even a tape DLSw See Data Link Switching. backup system or PCMCIA ports. The por- DMA See direct memory access. table computer and docking station are de- signed as two parts of the same system; you DMI See Desktop Management cannot swap computers and docking sta- Interface. tions from different manufacturers or even DNA See Digital Network Architecture. from different models. See also port replicator. DNS See Domain Name Service. DNS alias A host name that the Domain document database A carefully orga- Name Service (DNS) server knows points to nized collection of related documents; for another host. Computers always have one example, a set of technical support bulletins. real name, but they can also have several document instance In Standard Gener- aliases. A DNS alias is sometimes called a alized Markup Language (SGML), the text CNAME or a canonical name. component of a document as distinct from See also Domain Name Service. the structure of the document. DNS name server A server containing See also document type definition; Stan- information that is part of the Domain dard Generalized Markup Language. Name Service (DNS) distributed database, which makes computer names available to document management The catalog- client programs querying for name resolu- ing, storage, and retrieval of documents in tion on the Internet. a networked environment. In this context, a document may be text, scanned graphics, a See also Domain Name Service. spreadsheet, a form, a Web page, or any DNS Server log In Microsoft Windows other unique file. 2000 Server, a special log that records any Each file is tagged with information that in- events associated with running the Domain cludes the name of the original author, doc- Name Service (DNS) Server. ument description, creation date, and the See also Directory Service log; Event View- name of the application used to create the er; File Replication Service log. document. See also groupware; Lotus Notes; work- docking station A hardware system into flow software. which a portable computer fits so that it can be used as a full-fledged desktop computer. document root On a Web server, a di- Docking stations vary from simple port rep- rectory that contains the files, images, and licators that allow you access to parallel data you want to present to all users who and serial ports and a mouse to complete access the server with a browser. 118 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 119 Thursday, May 4, 2000 11:59 AM domain directory services document type definition Abbreviat- I In Microsoft Windows NT, a group of ed DTD. In Standard Generalized Markup computers, users, and network peripher- Language (SGML), the structural compo- als managed with a single set of account nent of a document as distinct from the ac- descriptions and security policies. A user tual data or content of the document. can log on to the local computer and be See also document instance; Standard authenticated to access just that one sys- Generalized Markup Language. tem, or a user can log on to a domain and be authenticated to access other servers documentation The instructions, tuto- within that domain. rials, specifications, troubleshooting ad- I In Lotus Notes, a domain is one or more vice, and reference guides that accompany a Notes servers that share the same Public computer program or a piece of hardware. Name and Address Book database. This Documentation can be in printed or online database contains information about the format. Early system documentation was users within the domain, including their e- often written by programmers and engi- mail addresses and other information. neers and was usually filled with technical See also domain name. jargon. Today’s documentation is generally better written and easier to understand. domain component In the Microsoft domain A description of a single com- Active Directory structure, a portion of a puter, a whole department, or a complete domain name. For example, in computer site, used for naming and administrative .sybex.com, each element of the name— purposes. computer, sybex, and com—is a domain Top-level domains must be registered to re- component. ceive mail from outside the organization; See also Active Directory. local domains have meaning only inside their own enterprise. Depending on the domain controller In Microsoft context, the term can have several slightly Windows NT, a server that stores and different meanings: shares domain information, including the central database of users, passwords, and I On the Internet, a domain is part of the permissions. Domain Name Service (DNS). I In Novell NetWare, a domain is a special A domain controller can be a primary do- area of memory where a new NetWare main controller, which stores the master Loadable Module (NLM) can be tested copy of the domain information, or a back- without the risk of corrupting the operat- up domain controller, which uses a replicat- ing system memory. ed version of this data to verify user logons and rights. I In IBM’s Systems Network Architecture (SNA), a domain represents all the terminals domain directory services Directory and other network resources controlled by a services that consist of one or more linked single processor or processor group. servers. Each domain within a network must 119 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 120 Thursday, May 4, 2000 11:59 AM domain name be managed and administered separately. DOS Acronym for Disk Operating Sys- Windows NT Server and IBM’s LAN Server tem. An operating system originally devel- both use domain directory services. oped by Microsoft for the IBM PC. See also global directory services. DOS existed in two similar versions: MS-DOS, developed and marketed by domain name In the Domain Name Ser- Microsoft for use with IBM-compatible vice (DNS), an easy-to-remember name computers, and PC-DOS, supported and that identifies a specific Internet host, as op- sold by IBM for use on computers manu- posed to the hard-to-remember numeric IP factured by IBM. address. See also MS-DOS. See also bang path. DOS client A workstation that boots Domain Name Service Abbreviated MS-DOS and gains access to the network DNS, sometimes referred to as Domain using either a NetWare shell or the Net- Naming System. A distributed addressing Ware DOS Requester software. system that resolves the domain name into the numeric IP address. DNS lets you use DOS prompt See MS-DOS prompt. the Internet without having to remember long lists of cryptic numbers. dot A synonym for the name of the cur- rent directory, usually invisible as its name The most common high-level domains on begins with a period. the Internet include: In Unix, a file whose name begins with a dot .com A commercial organization usually contains configuration informa- .edu An educational establishment such tion; you can customize your environment as a university by creating the appropriate dot file in the current directory or in your home directory. .gov A branch of the U.S. government See also current directory; dot dot; period .int An international treaty and double-period directories. organization .mil A branch of the U.S. military dot dot A synonym for the name of the .net A network provider parent directory to the current directory, usually invisible as its name begins with a .org A nonprofit organization period. Most countries also have unique domains See also current directory; dot; period and named after their international abbrevia- double-period directories. tion—for example, .uk for the United King- dom and .ca for Canada. dotted decimal A method of represent- See also IP address; name resolution. ing an IP address as four decimal numbers 120 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 121 Thursday, May 4, 2000 11:59 AM drag-and-drop separated by dots, or periods; for example, 2. To send information, such as font infor- mation or a PostScript file, from a computer to a printer. See also IP address. downsizing The redesign of mainframe- double-byte character set Abbreviat- based business applications to applica- ed DBCS. A method that uses two bytes to tions capable of running on smaller, less- hold the definition of the character rather expensive systems, often PC LANs. Client/ than the single byte used by the American server architecture is the model most often Standard Code for Information Interchange implemented during downsizing. (ASCII) or the Extended Binary Coded Dec- When applications are moved from large imal Interchange Code (EBCDIC). computer systems to PCs, security, integri- By utilizing two bytes instead one, the many ty, and overall control may be compro- international character sets in use these mised, and development and training costs days can be managed much more easily. can be high. However, a collection of ap- See also ASCII standard character set; propriately configured PCs, networked to- ASCII extended character set; Unicode. gether, can provide more than ten times the power for the same cost as a mainframe double-slash Notation used with a co- computer supporting remote terminals. lon to separate the communications proto- A more accurate term might be rightsizing, col from the host computer name in a to match the application requirements of Uniform Resource Locator (URL) as in the corporation to the capabilities of the http://www.sybex.com. hardware and software systems available. See also Uniform Resource Locator. See also outsourcing. downlevel trust In Microsoft Windows downtime The amount of time during 2000 Server, a trust explicitly established which a computer system is not available to between a Windows 2000 domain and a users, because of a hardware or software Windows NT 4 domain. failure. See also explicit trust; shortcut trust; trust downward compatibility See back- relationship; two-way transitive trust. ward compatibility. downlink The transmission of informa- DP See data processing. tion from a satellite to an earth station. drag-and-drop In a graphical user inter- See also uplink. face, to move a selected object onto another object with the mouse to initiate a process. download 1. In communications, to For example, if you drag a document icon transfer a file or files from one computer to and drop it onto a word processor’s icon, another over a network or using a modem. the program will run, and the document 121 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 122 Thursday, May 4, 2000 11:59 AM DRAM will be opened. To print a file, you can drag driver Jargon for device driver. the file to the printer icon using the mouse See also device driver. and then release the mouse button. You can also use drag-and-drop to copy a file from drop 1. The location in a multidrop line one disk to another or to move a marked where a tap is inserted to allow the connec- block of text to a new location inside a tion of a new device. word-processed document. 2. To lose part of a signal, usually uninten- DRAM See dynamic RAM. tionally, as in dropping bits. drive array The group of hard disk drop cable The cable used in thick Ether- drives used in one of the RAID (redundant net to connect a network device to a Multi- array of inexpensive disks) configurations. station Access Unit (MAU). The maximum cable length is 50 meters (165 feet). Some- See also redundant array of inexpensive times called a transceiver cable. disks. DS See digital signal. drive letter A designation used to specify a PC disk drive. For example, the first flop- DSCLIENT See directory service client. py disk drive is usually referred to as drive DSL See Digital Subscriber Line. A, and the first hard disk drive is usually re- ferred to as drive C. DSOM See Distributed System Object Model. drive mapping The technique of assign- ing a drive letter to represent a complete DSP See Digital Signal Processing. directory path statement. Novell NetWare DSR See Data Set Ready. supports four types of drive mapping: I Local drive mapping Maps drives to lo- DSU See Data Service Unit. cal hard disk and floppy disk drives DTD See document type definition. I Network drive mapping Maps drives to volumes and directories on the network DTE See data terminal equipment. I Network search drive mapping Maps DTR See Data Terminal Ready; Dedicat- drives to directories that should be ed Token Ring. searched if an application or file is not dual-attached station Abbreviated found in the current directory DAS. In the Fiber Distributed Data Inter- I Directory map object Maps drives to di- face (FDDI), a device attached to both of rectories that contain frequently used the dual, counter-rotating rings. Concen- files, such as applications, without having trators, bridges, and routers often use DAS to specify the actual physical location of connections to provide fault tolerance. In the file contrast, a single attached station (SAS) See also Directory Map object. connects to only one ring. 122 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 123 Thursday, May 4, 2000 11:59 AM Dynamic Data Exchange dual-homed host A network server DVD See digital video disc. configured with two network interface DVD-E See digital video disc-erasable. cards, each connected to a different net- work. Dual-homed hosts are often used DVD-R See digital video disc- with firewalls to increase network security. recordable. See also firewall; proxy server. DVD-ROM See digital video disc-ROM. dual homing In Fiber Distributed Data dynamic adaptive routing See dy- Interface (FDDI), a method of cabling con- namic routing. centrators and stations in a tree configura- dynamic bandwidth allocation A tion, providing an alternative route to the method of bandwidth allocation that sub- FDDI network should the primary connec- divides the available bandwidth between tion fail. multiple applications almost instanta- dual in-line package Abbreviated DIP. neously, to provide each application with A standard housing constructed of hard just the amount of bandwidth that it cur- plastic commonly used to hold an integrat- rently needs. ed circuit. The circuit’s leads are connected Dynamic Data Exchange Abbreviated to two parallel rows of pins designed to fit DDE. A technique used for application-to- snugly into a socket; these pins may also be application communications, available in soldered directly to a printed circuit board. several operating systems, including Mi- See also DIP switch. crosoft Windows, Macintosh, and OS/2. When two or more programs that support dumb terminal A combination of key- DDE are running at the same time, they can board and screen that has no local comput- exchange data and commands, by means of ing power, used to input information to a conversations. A DDE conversation is a large, remote computer, often a minicom- two-way connection between two applica- puter or a mainframe. The remote comput- tions, used to transmit data by each pro- er provides all the processing power for the gram alternately. system. DDE is used for low-level communications See also diskless workstation; intelligent that do not need user intervention. For ex- terminal; network computer; thin client. ample, a communications program might feed stock market information into a duplex In asynchronous transmissions, spreadsheet program, where that data can the ability to transmit and receive on the be displayed in a meaningful way and recal- same channel at the same time; also referred culated automatically as it changes. to as full duplex. Half-duplex channels can DDE has largely been superseded by Object transmit only or receive only. Linking and Embedding (OLE). See also communications parameters. See also Object Linking and Embedding. 123 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 124 Thursday, May 4, 2000 11:59 AM dynamic disk dynamic disk In Microsoft Windows Dynamic Link Library Abbreviated 2000, a hard disk that is available only to DLL. A program module that contains ex- Windows 2000 and not available from any ecutable code and data that can be used by other operating system. A dynamic disk applications, or even by other DLLs, in per- does not use primary and extended parti- forming a specific task. tions to divide the available space into log- DLLs are used extensively throughout the ical units. family of Microsoft Windows products. To create a dynamic disk, use the Disk DLLs may have filename extensions of Management utility to convert a basic disk .DLL, .DRV, or .FON. into a dynamic disk. Dynamic disks allow The DLL is linked into the application only you to create, delete, and extend fault-tol- when the program runs, and it is unloaded erant and multidisk volumes without re- again when no longer needed. If two DLL starting the operating system. Windows applications are running at the same time 2000 RAID (redundant array of inexpen- and both perform a particular function, only sive disks) services are available only on dy- one copy of the code for that function is namic disks. loaded, for more efficient use of limited See also basic disk. memory. Another benefit of using dynamic linking is that the .EXE files are not as large Dynamic DNS Abbreviated DDNS. In as they would be, because frequently used Microsoft Windows 2000 Server, a mecha- routines can be put into a DLL rather than nism that allows Dynamic Host Configura- repeated in each .EXE file that uses them. A tion Protocol (DHCP) and Windows 2000 smaller .EXE file means saved disk space and clients to update Domain Name Service faster program loading. (DNS) records dynamically, rather than by dynamic RAM Abbreviated DRAM, the traditional method of manually adding pronounced “dee-ram.” A common type of the new records to static DNS zone files. computer memory that uses capacitors and See also Domain Name Service. transistors storing electrical charges to rep- resent memory states. These capacitors lose Dynamic Host Configuration Protocol their electrical charge, so they need to be re- freshed every millisecond, during which Abbreviated DHCP. A system based on net- time they cannot be read by the processor. work interface card addresses that is used to allocate IP addresses and other configura- DRAM chips are small, simple, cheap, easy tion information automatically for net- to make, and hold approximately four worked systems. DHCP is an update of the times as much information as a static RAM Bootstrap Protocol. (SRAM) chip of similar complexity. How- ever, they are slower than SRAM. See also Bootstrap Protocol; hardware ad- dress; IP address; Transmission Control dynamic routing A routing technique Protocol/Internet Protocol. that allows the route that a message takes to 124 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 125 Thursday, May 4, 2000 11:59 AM DynaText change, as the message is in transit through Dynamic volumes can include simple, the network, in response to changing net- striped, spanned, and RAID-5 components work conditions. Conditions forcing a route and can exist only on dynamic disks. change might include unusually heavy traffic See also basic disk; dynamic disk. on a particular section of the network or a cable failure. Also known as dynamic adap- DynaText A form of electronic docu- tive routing. ment and viewer used in Novell NetWare for online manuals. You can use DynaText dynamic volume In Microsoft Win- directly from the CD, or you can install it on dows 2000, a logical hard disk volume cre- the server or on a workstation. Replaces ated by Disk Management. Electrotext. 125 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 126 Thursday, May 4, 2000 11:59 AM E E E See exa-. EB See exabyte. E1 A point-to-point, dedicated, EBCDIC See Extended Binary Coded 2.048Mbps communications circuit capa- Decimal Interchange Code. ble of supporting thirty-two 64Kbps chan- echo 1. A transmitted signal that is re- nels used as 30 voice channels, 1 control flected back to the sender strongly enough so channel, and 1 synchronization and fram- that it can be distinguished from the original ing channel. The European equivalent of signal; often encountered on long-distance North America’s T1. telephone lines and satellite links. E1 circuits carry more channels than the 24 2. A form of repetition, used as a mecha- channels used in T1 systems, and repeaters nism in testing network nodes, in which are required every 6000 feet when copper each receiving station on the network ech- wire is used. oes a message back to the main server or E2 A European point-to-point, dedicat- host computer. ed, 8.848Mbps communications circuit equivalent to four E1 circuits. E2 is the Eu- echo cancellation A mechanism used to ropean equivalent of North America’s T2 control echoes on communications links and is rarely used. such as satellite links. The modem checks for a delayed duplica- E3 A European point-to-point, dedicated, tion of the original signal and adds a re- 34.368Mbps communications circuit versed version of this transmission to the equivalent to 16 E1 circuits. The European channel on which it receives information. equivalent of North America’s T3. This process effectively removes the echo E4 A European point-to-point, dedicated, without affecting the incoming signal. 139.26Mbps communications circuit ECNE See Master Certified Novell equivalent to 4 E3 or 64 E1 circuits. Engineer. E5 A European point-to-point, dedicated, EDI See electronic data interchange. 565.148Mbps communications circuit equivalent to 4 E4 or 256 E1 circuits. EDO RAM Abbreviation for extended data out RAM. A type of RAM that keeps EAP See Extensible Authentication data available to the processor while the Protocol. next memory access is being initialized, eavesdropping The process of gathering thus speeding overall access times. EDO information about a target network by lis- RAM is significantly faster than conven- tening in on transmitted data. tional dynamic RAM. 126 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 127 Thursday, May 4, 2000 11:59 AM electromagnetic interference EDP See data processing. I Define media types, as well as connections and terminations EEMS See Enhanced Expanded Mem- I Provide a basis for interoperation ory Specification. between competing products and services effective rights In Novell Directory Ser- in wiring, design, installation, and vices (NDS), any rights an object can use to management look at or change a specific directory, file, I Allow for the wiring of a building before or other object. the definition of the products that will use Effective rights are recalculated every time that wiring, and allow for elegant future an object attempts such an operation and expansion are controlled by the Inherited Rights Filter, EIA/TIA 586 applies to all unshielded the trustee assignment, and the specified se- twisted-pair wiring that works with Ether- curity restrictions. Effective rights are of net, Token Ring, ISDN, and other net- two types: working systems. I Object rights determine what a user can See also cabling standards; Category 1–5. do with an object. I Property rights control a user’s access to EIDE See Enhanced IDE. that object. EIGRP See Enhanced Interior Gateway See also Inherited Rights Filter; Novell Routing Protocol. Directory Services; rights; trustee assignments. EISA See Extended Industry Standard Architecture. EFS See Encrypted File System. electromagnetic interference Abbre- EGP See External Gateway Protocol. viated EMI. Any electromagnetic radiation released by an electronic device that dis- EIA See Electronic Industries rupts the operation or performance of an- Association. other device. EIA/TIA 586 A standard, jointly defined EMI is produced by many sources com- by the Electronic Industries Association monly found in an office environment, in- and the Telecommunications Industry As- cluding fluorescent lights, photocopiers, sociation (EIA/TIA), for telecommunica- and motors such as those used in elevators. tions wiring used in commercial buildings. EMI is also produced by natural atmo- The standard is designed to do the spheric or solar activity. following: See also Class A certification; Class B cer- I Specify a generic wiring system for all tification; Federal Communications Com- commercial buildings mission; radio frequency interference. 127 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 128 Thursday, May 4, 2000 11:59 AM electronic commerce electronic commerce The buying and uals, to a predefined group, or to all users selling of goods and services over the Inter- on the system. When you receive a message, net. Electronic commerce may also involve you can read, print, forward, answer, or de- business-to-business transactions in the ex- lete it. change of purchase orders, invoices, and An e-mail system may be implemented on a other electronic documents. peer-to-peer network, a client/server archi- electronic data interchange Abbrevi- tecture, a mainframe computer, or on a ated EDI. A method of electronically ex- dial-up service, such as America Online. E- changing business documents, including mail is by far the most popular Internet ap- bills of materials, purchase orders, and plication, with well over 80 percent of In- invoices. ternet users taking advantage of the service. E-mail has several advantages over conven- Customers and suppliers can establish an tional mail systems, including: EDI network by means of Open Systems In- terconnect (OSI) standards or by using pro- I E-mail is fast—very fast when compared prietary products. Widely accepted with conventional mail. standards include ANSI X.12, ISO 9735, I If something exists on your computer as a and CCITT X.435. file—text, graphical images, even pro- gram files and video segments—you can electronic data processing See data usually send it as e-mail. processing. I E-mail is very extensive. You can now Electronic Industries Association Ab- send e-mail to well over half the countries breviated EIA. A trade association repre- in the world. senting American manufacturers in The problems associated with e-mail are standards organizations. The EIA has similar to those associated with online com- published and formalized several important munications in general, such as security, standards, including RS-232-C, RS-422, privacy (always assume that your e-mail is RS-423, RS-449, RS-485, and RS-530. not private), and the legal status of docu- Standards having to do with communica- ments exchanged via e-mail. tions are produced jointly with the Tele- communications Industry Association. See also mailbox; Multipurpose Internet Mail Extension; voice mail. For more information on the EIA, see www.eia.org. element A unit of structure in Hyper- See also EIA/TIA 586. Text Markup Language (HTML), such as a title or a list. Some elements have start and electronic mail The use of a network to stop tags; others have only a single tag. Cer- transmit text messages, memos, and re- tain elements can be nested within other ports; usually referred to as e-mail. Users elements. can send a message to one or more individ- See also HyperText Markup Language; tag. 128 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 129 Thursday, May 4, 2000 11:59 AM enable elevator seeking A technique that al- rent system configuration that can be used lows the server hard disk head to access files to repair a system that will not restart. in the direction that the head is already trav- See also Recovery Console; safe mode. eling across the disk, rather than in the or- der in which they were requested. This EMI See electromagnetic interference. feature allows the drive heads to operate continuously and thus improves disk per- EMM See expanded memory manager. formance and minimizes disk-head seek emoticon A collection of text characters times. often used in e-mail and posts to news- ELF See extremely low-frequency groups to signify emotions. emission. An emoticon can be as simple as including EMA See Enterprise Memory <g> or <grin> in your text, an indication Architecture. that the writer is joking, and as complex as some of the smiley faces, which are all de- emacs A popular Unix editor, written by signed to be read sideways, such as the wink Richard Stallman, founder of the Free Soft- ;-) or the frown :-(. ware Foundation. See also Internet abbreviations. The name emacs is a contraction of “editing macros,” but it is much more than a simple EMS See Expanded Memory text editor and includes extensions for all Specification. sorts of common tasks, ranging from com- piling and debugging programs to reading emulator A device built to work exactly and sending e-mail. You can even extend like another device—hardware, software, emacs yourself as the editing commands are or a combination of both. written in the Lisp programming language. For example, a terminal emulation pro- See also Free Software Foundation; vi. gram lets a PC pretend to be a terminal at- tached to a mainframe computer or to an e-mail See electronic mail. online service by providing the control codes that the remote system expects to re- e-mail address The addressing informa- ceive. In printers, some brands emulate tion required for an e-mail message to reach popular models such as Hewlett-Packard’s the correct recipient. LaserJet line. See also bang path; Internet address; enable To turn a function on or allow mailbox. something to happen. When a function is Emergency Repair Disk Abbreviated enabled, it is available for use. In a graphi- ERD. In Microsoft Windows 2000, a flop- cal user interface, enabled menu commands py disk created by the Backup program. An are often shown in black type. ERD contains information about the cur- See also disable. 129 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 130 Thursday, May 4, 2000 11:59 AM Encapsulated PostScript Encapsulated PostScript Abbreviated See also codec; decode; decryption; EPS. The file format of the PostScript page- uuencode. description language. Encrypted File System In Microsoft The EPS standard is device independent, so images can easily be transferred between Windows 2000, a feature that lets mobile applications, and they can be sized and out- users, who are concerned with the security put to different printers without any loss of of their files in the case of unauthorized image quality or distortion. access to their computers, encrypt designat- ed files and directories using a public key The EPS file contains the PostScript com- encryption scheme. mands needed to recreate the image, but the image itself cannot be displayed on a Encrypting File System Abbreviated monitor unless the file also contains an op- EFS. In Microsoft Windows 2000, a file sys- tional preview image stored in TIFF or tem used to encrypt files and folders on an PICT format. NTFS 5 hard disk. You can print an EPS file only on a Post- Script-compatible laser printer, and the encryption The process of encoding in- printer itself determines the final printing formation in an attempt to make it secure resolution. A laser printer might be capable from unauthorized access, particularly dur- of 600 dpi, whereas a Linotronic printer is ing transmission. The reverse of this process capable of 2450 dpi. is known as decryption. encapsulation The process of inserting Two main encryption schemes are in com- the frame header and data from a higher- mon use: level protocol into the data frame of a I Private (Symmetrical) Key An encryp- lower-level protocol. tion algorithm based on a private encryp- See also tunneling. tion key known to both the sender and the recipient of the information. The encrypt- enclosure A term for a file—text, fax, bi- ed message is unreadable and can be nary, or image—sent as a part of an e-mail transmitted over nonsecure systems. message. Sometimes called an attachment. I Public (Asymmetrical) Key An encryp- See also Multipurpose Internet Mail tion scheme based on using the two halves Extension. of a long bit sequence as encryption keys. encode 1. To compress a video file using Either half of the bit sequence can be used a codec so that the file can be transmitted in to encrypt the data, but the other half is re- the shortest possible time. quired to decrypt the data. 2. To convert a binary file into a form suit- See also Data Encryption Standard; Pretty able for data transmission. Good Privacy; ROT-13. 130 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 131 Thursday, May 4, 2000 11:59 AM Enhanced Interior Gateway Routing Protocol encryption key A unique and secret During the mainframe computer era, end number used to encrypt data to protect it users were people who received output from unauthorized access. from the computer and used that output in their work. They rarely, if ever, actually end-of-file Abbreviated EOF. A special saw the computer, much less learned to use code placed after the last byte in a file that it themselves. Today, end users often write indicates to the operating system that no macros to automate complex or repetitive more data follows. tasks and sometimes write procedures using An end-of-file code is needed because disk command languages. space is assigned to a file in blocks, and the Enhanced Expanded Memory file may not always terminate at the end of Specification Abbreviated EEMS. A re- a block. In the ASCII system, an EOF is rep- vised version of the original Lotus-Intel- resented by the decimal value 26 or by the Microsoft Expanded Memory Specification Ctrl+Z control character. (LIM EMS) that lets MS-DOS applications use more than 640KB memory space. end node A networked node such as a See also Expanded Memory Specification. PC that can only send and receive informa- tion for its own use; it cannot route or for- Enhanced IDE An extension to the Inte- ward information to another node. grated Drive Electronics (IDE) interface end-of-text Abbreviated ETX. A charac- standard, which supports hard disks as large as 8.4GB (IDE supports hard disks of ter used in computer communications to in- up to 528MB) and transfer rates of up to dicate the end of a text file. 13.3MBps (IDE allows rates of up to In the ASCII system, an ETX is represented 3.3MBps). by the decimal value 3 or by the Ctrl+C con- See also Integrated Drive Electronics; trol character. A different symbol, end-of- Small Computer System Interface. transmission (EOT, ASCII 4, or Ctrl+D) is used to indicate the end of a complete Enhanced Interior Gateway Routing transmission. Protocol Abbreviated EIGRP. A propri- etary link-state distance-vector routing pro- end-of-transmission Abbreviated tocol from Cisco, first released in 1994. EOT. A character used in computer com- EIGRP improves performance by using in- munications to indicate the end of a trans- formation derived from distance-vector mission. In the ASCII system, an EOT is protocols, but also includes an algorithm represented by the decimal value 4 or by the for removing transient loops in possible Ctrl+D control character. routes, which reduces the complexity of the end user Often refers to people who use calculations required. an application to produce their own results See also distance vector algorithm; Interior on their own computer or workstation. Gateway Routing Protocol. 131 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 132 Thursday, May 4, 2000 11:59 AM Enhanced Small Device Interface Enhanced Small Device Interface Ab- service features to other networks. ENS in- breviated ESDI. A popular hard disk, flop- cludes StreetTalk Directory Assistance, the py disk, and tape drive interface standard, Banyan Security Service, and Banyan Net- capable of a data-transfer rate of 10 to work Management. 20Mbps. ESDI is most often used with large Specific versions of ENS are available for hard disks. Novell NetWare, SCO Unix, and HP-UX so See also Integrated Drive Electronics; that servers running those operating sys- Small Computer System Interface. tems can interoperate and share manage- ment in a network with VINES servers. ENS See Enterprise Network Services. See also Banyan VINES. Enter key Also known as the Return key, Enterprise Systems Connection Ab- short for carriage return. The key that indi- breviated ESCON. A set of products and ser- cates the end of a command or the end of vices from IBM that provide direct channel- user input from the keyboard. to-channel connections between ES/9000 enterprise A term used to encompass an mainframes and peripheral devices over 10 entire business group, organization, or cor- to 17MBps fiber-optic links. poration, including all local, remote, and envelope delay See delay distortion. satellite offices. environment 1. The complete set of Enterprise CNE See Master Certified hardware and software resources made Novell Engineer. available to any user of a system. Enterprise Memory Architecture Ab- 2. The operating system that a program breviated EMA. In Microsoft Windows needs in order to execute. For example, a 2000, a mechanism that lets applications ad- program may be said to be running in the dress as much as 64GB of virtual memory. Unix environment. enterprise network A network that EOF See end-of-file. connects every computer in every location of a business group, organization, or cor- EOT See end-of-transmission. poration and runs the company’s mission- EPS See Encapsulated PostScript. critical applications. equalization The process of balancing a In many cases, an enterprise network in- circuit by reducing frequency and phase cludes several types of computers running distortion so that it passes all expected fre- several different operating systems. quencies with equal efficiency. Enterprise Network Services Abbre- ERD See Emergency Repair Disk. viated ENS. A software product based on Banyan Systems’ StreetTalk Directory Ser- error The difference between the expect- vice for VINES that brings global directory ed and the actual. 132 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 133 Thursday, May 4, 2000 11:59 AM escape sequence In computing, the way that the operating Good error handling manages unexpected system reports unexpected, unusual, im- events or wrongly entered data gracefully, possible, or illegal events is by displaying an usually by opening a dialog box to prompt error number or error message. Errors the user to take the appropriate action or to range from trivial, such as an attempt to enter the correct information. Badly written write a file to a disk drive that does not con- programs may simply stop running when tain a disk, to fatal, such as when a serious the wrong data is entered or when an unan- operating system bug renders the system ticipated disk error occurs. useless. error message A message from the pro- In communications, errors are often caused gram or the operating system that contains by line noise and signal distortion. Parity or information about a condition that requires cyclical redundancy check (CRC) informa- some human intervention to solve. tion is often added as overhead to the data Error messages can indicate relatively triv- stream, and techniques such as error detec- ial problems, such as a disk drive that does tion and correction are employed to detect not contain a disk, as well as fatal problems, and correct as many errors as possible. such as when a serious operating system See also attenuation; crosstalk; error bug renders the system useless and requires handling; error message; error rate; a system reboot. parity error. error rate In communications, the ratio between the number of bits received incor- error detection and correction A rectly and the total number of bits in the mechanism used to determine whether transmission, also known as bit error rate transmission errors have occurred and, if (BER). so, to correct those errors. Some methods for determining error rate use Some programs or transmission protocols larger or logical units, such as blocks, pack- simply request a retransmission of the af- ets, or frames. In these cases, the measure- fected block of data if an error is detected. ment of error rate is expressed in terms of the More complex protocols attempt to both number of units found to be in error out of detect and determine at the receiving end the total number of units transmitted. what the correct transmission should have escape code See escape sequence. been. Escape key The key on the keyboard la- See also checksum; cyclical redundancy beled Esc. The Escape key generates an es- check; forward error correction; Hamming cape code, ASCII 27. In most applications, code; parity. pressing the Escape key cancels the current command or operation. error handling The way that a program copes with errors or exceptions that occur escape sequence A sequence of charac- as the program is running. ters, beginning with Escape (ASCII 27) and 133 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 134 Thursday, May 4, 2000 11:59 AM ESCON followed by one or more other characters, And the disadvantages include: that performs a specific function. Some- I Heavy traffic can slow down the network. times called an escape code. Escape sequences are often used to control I A break in the main cable can bring down printers or monitors, which treat them as large parts of the network. commands and act upon them rather than I Troubleshooting a bus topology can processing them as characters to print or prove difficult. display. See also 10/100; 100VG-AnyLAN; 10Base2; ESCON See Enterprise Systems 10Base5; 10BaseF; 10BaseT; demand pri- Connection. ority; Fast Ethernet; Gigabit Ethernet. ESDI See Enhanced Small Device Interface. Ethernet address The address assigned to a network interface card by the original Ethernet A popular network protocol manufacturer or by the network adminis- and cabling scheme with a transfer rate of trator if the card is configurable. 10Mbps, originally developed at Xerox in 1970 by Dr. Robert Metcalf. Ethernet uses This address identifies the local device ad- a bus topology, and network nodes are con- dress to the rest of the network and allows nected by either thick or thin coaxial cable, messages to reach the correct destination. fiber-optic cable, or twisted-pair cable. Also known as the media access control (MAC) or hardware address. Ethernet uses CSMA/CD (Carrier Sense Multiple Access/Collision Detection) to Ethernet meltdown An event that caus- prevent network failures or collisions when es saturation on an Ethernet-based system, two devices try to access the network at ex- often the result of illegal or misdirected actly the same time. packets. An Ethernet meltdown usually The original DIX (Digital Equipment, lasts for only a short period of time. Intel, Xerox), or Blue Book, standard has evolved into the slightly more complex Ethernet packet A variable-length unit IEEE 802.3 standard and the ISO’s 8802.3 in which information is transmitted on an specification. Ethernet network. The advantages of Ethernet include: An Ethernet packet consists of a synchroni- I It’s easy to install at a moderate cost. zation preamble, a destination address, a source address, a field that contains a type I Technology is available from many sourc- code indicator, a data field that can vary es and is very well known. from 46 to 1500 bytes, and a cyclical redun- I It offers a variety of cabling options. dancy check (CRC) that provides a statisti- I It works very well in networks with only cally derived value used to confirm the occasional heavy traffic. accuracy of the data. 134 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 135 Thursday, May 4, 2000 11:59 AM execute ETHERNET PACKET EtherTalk An implementation of the See also application log; Directory Service Ethernet LAN developed for Apple com- log; DNS Server log; File Replication Ser- puters, designed to work with the Apple- vice log; security log; system log. Share network operating system. exa- Abbreviated E. A prefix meaning one EtherTalk operates over coaxial cable at the quintillion, or 1018. In computing, the prefix Ethernet transfer rate of 10Mbps, much means 1,152,921,504,606,846,976, or the faster than the 230.4Kbps rate available power of 2 closest to one quintillion (260). with AppleTalk. Each networked Macin- tosh computer must be supplied with a spe- exabyte Abbreviated EB. 1 quintillion cial EtherTalk network interface card. bytes, or 1,152,921,504,606,846,976 bytes. ETX See end-of-text. exclusive container administrator In Eudora A popular and widely used Novell NetWare, a special type of container e-mail application originally developed by administrator who is given the rights to a Steve Dorner at the University of Illinois container and all the objects within that and now available from Qualcomm, Inc. container. The Inherited Rights Filter pre- European Laboratory for Particle vents other administrators from having Physics See Conseil Européen pour la rights in the container. Researche Nucléaire. See also container administrator; Inherited even parity See parity. Rights Filter. Event Log service A Microsoft Win- executable file Any file that can be exe- dows 2000 service that logs important ap- cuted by the operating system. Some exe- plication, security, and system events into cutable files contain compiler binary the event log. instructions, and others are text files con- taining commands or shell scripts. Event Viewer In Microsoft Windows 2000, a utility that displays the contents of execute 1. To run a program, com- the system logs. mand, or script. 135 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 136 Thursday, May 4, 2000 11:59 AM execute permission 2. One of the permissions assigned to a file window through which segments of expand- or directory; you can only execute a file ed memory can be seen, but only one segment when the execute permission is enabled. at a time. execute permission An access permis- expanded memory manager Abbrevi- sion on a file or directory that gives you per- ated EMM. A device driver that supports mission to execute the file or to access the the software portion of the Expanded contents of the directory. Memory Specification (EMS) in an IBM- compatible computer. expandability The ability of a system to accommodate expansion. In hardware, this Expanded Memory Specification Ab- may include the addition of more memory, breviated EMS. The original version of the more or larger disk drives, and new adapt- Lotus-Intel-Microsoft Expanded Memory ers. In software, expandability may include Specification (LIM EMS), which let MS- the ability of a network to add users, nodes, DOS applications use more than 640KB of or connections to other networks. memory space. expanded memory An MS-DOS mech- These days Microsoft Windows running in anism by which applications can access protected mode on 80386 and later proces- more than the 640KB of memory normally sors is free of this limitation. available to them. The architecture of the early Intel processors restricted the original expansion board A printed circuit IBM PC to accessing 1MB of memory, board that plugs into a computer’s expan- 640KB of which was available for applica- sion bus to provide added capabilities. Also tions; the remaining 384KB was reserved called an adapter. for system use, the BIOS, and the video sys- Common expansion boards include video tem. At that time, 640KB was more than ten adapters, joy-stick controllers, and input/ times the amount of memory available in output (I/O) adapters, as well as other de- other personal computers. However, as vices, such as internal modems, CD-ROMs, both applications and MS-DOS grew, they and network interface cards (NICs). One began to run out of room. expansion board can often support several The Expanded Memory Specification LIM different devices. Some current PC designs 4.0 let programs running on the Intel family incorporate many of the functions previ- of processors access as much as 32MB of ex- ously performed by these individual adapt- panded memory. The expanded memory ers on the motherboard. manager (EMM) creates a block of addresses into which data (held in memory above the expansion bus An extension of the main 1MB limit) is swapped in and out as needed computer bus that includes expansion slots by the program. In other words, a 64KB seg- for use by compatible adapters, such as ment of addressable memory creates a small memory boards, video adapters, hard-disk 136 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 137 Thursday, May 4, 2000 11:59 AM Extended Industry Standard Architecture controllers, and SCSI (Small Computer Sys- automatically established if they are in the tem Interface) interface cards. same forest See also downlevel trust; forest; shortcut expansion slot One of the connectors trust; trust relationship; two-way transitive on the expansion bus that gives an adapter trust. access to the system bus. You can install as many additional adapters as there are ex- extended ASCII character set See pansion slots inside your computer. ASCII extended character set. For portable computers, an expansion slot is often supplied by a PCMCIA connection Extended Binary Coded Decimal Inter- designed to accept a PC Card. change Code Abbreviated EBCDIC; pronounced “eb-se-dic.” EBCDIC is the expansion unit An external housing character set commonly used on large IBM available with certain portable computers mainframe computers, most IBM minicom- designed to contain additional expansion puters, and computers from many other slots and maintain a connection to the main manufacturers. expansion bus in the computer’s system unit. It is an 8-bit code, allowing 256 different See also port replicator. characters (see Appendix D). Unlike ASCII, the placement of the letters of the alphabet explicit rights In Novell Directory Ser- in EBCDIC is discontinuous. Also, there is vices (NDS), any rights granted directly to a no direct character-to-character match user for a directory or other NDS object. when converting from EBCDIC to ASCII; Explicit rights always override inherited some characters exist in one set but not in rights. the other. See also inherited rights. See also American Standard Code for In- formation Interchange; double-byte char- explicit security equivalence In Nov- acter set; ISO 10646; Unicode. ell Directory Services (NDS), a technique used to give one trustee the same rights as Extended Industry Standard another trustee. Explicit security equiva- Architecture Abbreviated EISA, pro- lence can be assigned with group member- nounced “ee-sah.” A PC bus standard that ship, an Organizational Role, or the extends the traditional AT-bus to 32 bits trustee’s Security Equal To property. and allows more than one processor to share the bus. See also implied security equivalence; security equivalence. EISA was developed by the so-called Gang of Nine (AST Research, Compaq Computer explicit trust In Microsoft Windows Corporation, Epson, Hewlett-Packard, NEC, 2000 Server, a trust explicitly established Olivetti, Tandy, Wyse Technology, and Ze- between two Windows 2000 domains. This nith Data Systems) in reply to IBM’s introduc- is in addition to the built-in transitive trusts tion of its proprietary MCA (Microchannel 137 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 138 Thursday, May 4, 2000 11:59 AM extended LAN Architecture). EISA maintains compatibility Extended Memory Specification Ab- with the earlier ISA (Industry Standard Archi- breviated XMS. A standard developed by tecture), and it also provides for additional Microsoft, Intel, Lotus, and AST Research features introduced by IBM in the MCA stan- that became the preferred way of accessing dard. EISA accepts ISA expansion cards and extended memory in the PC. MS-DOS in- so, unlike MCA, is compatible with earlier cludes the extended memory device driver systems. EISA has been eclipsed by Peripheral HIMEM.SYS, and this command or an Control Interconnect-based systems. equivalent must be present in CONFIG.SYS to allow you to access extended memory. See also local bus; PCI local bus; PC Mem- ory Card International Association. Extensible Authentication Protocol Abbreviated EAP. In Microsoft Windows extended LAN A term used to describe a 2000 Server, a mechanism that allows fu- network that consists of a series of LANs ture authentication schemes to be added to connected by bridges. the operating system quickly and easily. extended memory Memory beyond See also Challenge-Handshake Authenti- 1MB on computers using the Intel 80286 cation Protocol. and later processors, not configured for ex- Extensible Markup Language Abbre- panded memory. viated XML. A technology, based on Stan- PCs based on the early Intel processors dard Generalized Markup Language could access only 1MB of memory, of (SGML), that allows the data on a Hyper- which 640KB was available for applica- Text Markup Language (HTML) page to tions, and the remaining 384KB was re- be described in terms of the information it served for MS-DOS, the BIOS, and video represents. settings. See also document type definition; Hyper- Later processors can access more memory, Text Markup Language. but it was the 80386 with its ability to ad- dress 4GB of memory that really made ex- external command A command that is tended memory usable. Also, Microsoft a separate program, and not built in to the operating system. FORMAT, BACKUP, Windows and other operating systems run- and FDISK are examples of external ning on Intel processors using the protected commands. mode of the 80386 and later processors can access all the available system memory in See also internal command. the same way. External Gateway Protocol Abbrevi- extended memory manager A device ated EGP. A routing protocol used to ex- driver that supports the software portion of change network availability information the Extended Memory Specification in an among organizational networks. EGP indi- IBM-compatible computer. cates whether a given network is reachable, 138 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 139 Thursday, May 4, 2000 11:59 AM extremely low-frequency emission but it does not evaluate that information or of electronic commerce and collaboration. make routing or priority decisions. Those parts of an extranet outside the fire- See also Border Gateway Protocol. wall contain their own set of security safe- guards, allowing only limited access for external modem A stand-alone mo- specific purposes. dem, separate from the computer and con- See also intranet. nected to it by a serial cable. LEDs on the front of the chassis indicate the current mo- extremely low-frequency emission dem status. An external modem can be used Abbreviated ELF. Radiation emitted by a with different computers at different times computer monitor and other common elec- and also with different types of computers. trical appliances. external reference In Novell NetWare, ELF emissions fall into the range of 5 to a pointer to a NetWare Directory Services 2000 hertz and decline with the square of (NDS) object that is not located on the cur- the distance from the source. Emissions are rent server. not constant around a monitor; they are extranet Originally coined as a term to higher from the sides and rear and weakest describe any network in which part of the from the front of the screen. Low-emission network was protected behind a firewall models are available, and laptop computers and part of the network was accessible from with an LCD display do not emit any ELF the Internet. fields. In current usage, an extranet describes a See also electromagnetic interference; technology that allows different corporate radio frequency interference; very low- intranets to communicate for the purposes frequency emission. 139 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 140 Thursday, May 4, 2000 11:59 AM facsimile F facsimile See fax. far-end crosstalk Abbreviated FEXT. Interference that occurs when signals on fading In both electrical and wireless sys- one twisted-pair are coupled with another tems, a decrease in a signal’s strength. pair as they arrive at the far end of a multi- Fading may be due to physical obstructions pair cable system. of the transmitter or receiver, to distance FEXT becomes a problem on short loops from the source of the transmission, or to supporting high-bandwidth services such as some form of external interference from oth- Very-High-Bit-Rate Digital Subscriber Line er signals or from atmospheric conditions. (VDSL) because of the high carrier frequen- fail-safe system Any computer system cies used. that is designed to keep operating, without See also crosstalk; near-end crosstalk. losing data, when part of the system seri- ously malfunctions or fails completely. Fast Ethernet A term applied to the IEEE 802.3 Higher Speed Ethernet Study fail-soft system Any computer system Group proposals, which were originally de- that is designed to fail gracefully, with the veloped by Grand Junction Networks, minimum amount of data or program de- 3Com, SynOptics, Intel, and others. Also struction, when part of the system malfunc- known as 100BaseT. tions. Fail-soft systems close down non- essential functions and operate at a reduced Fast Ethernet modifies the existing Ethernet capacity until the problem is resolved. standard to allow speeds of 10Mbps or 100Mbps or both and uses the CSMA/CD fake root A subdirectory that functions access method. as the root directory. The official standard defines three physical- Fake roots can be useful with network ap- layer specifications for different cabling plications that must be installed in the root types: directory. You can install the application in I 100BaseTX for two-pair Category 5 un- a subdirectory and then map a fake root on shielded twisted-pair the file server to the subdirectory contain- ing the application. Many Web servers use I 100BaseT4 for four-pair Category 3, 4, or a fake root. 5 unshielded twisted-pair I 100BaseFX for fiber-optic cable fall back A technique used by modems to adjust their data rate in response to chang- See also 100VG-AnyLAN; demand priority. ing line conditions. Fast IP A technology from 3Com Corpo- FAQ See frequently asked questions. ration that gives certain types of network 140 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 141 Thursday, May 4, 2000 11:59 AM fault tolerance traffic, such as real-time video, a higher pri- addressing scheme which restricts the ority than other, less urgent network traffic maximum hard-disk size to 2.6GB. Also, such as e-mail messages. FAT16 is inefficient in disk-space utiliza- 3Com achieves this using what it calls pol- tion as the default cluster size can be as icy management. A workstation requests a large as 32KB. certain level of priority, tags the data ac- See also FAT32; file allocation table. cordingly, and begins the transmission. When the transmission is complete, the FAT32 In Microsoft Windows 95 (release workstation indicates that to the network, 2) and later versions of Windows, a file al- and previously reserved resources are freed location table that uses a 32-bit cluster ad- up for use. dressing scheme to support hard disks larger than 2.6GB, as well as a default clus- See also IP over ATM; IP switching; quality ter size of as small as 4KB. FAT32 can sup- of service. port hard disks of up to 2 terabytes in size. Fast IR A 4Mbps extension to the Serial See also FAT16; file allocation table. Infrared Data Link Standard that provides wireless data transmission between IrDA- fatal error An operating system or appli- compliant devices. cation program error from which there is See also Infrared Data Association. no recovery without reloading the program or rebooting the operating system. Fast SCSI A version of the SCSI-2 inter- fault management One of the five basic face that can transfer data 8 bits at a time at types of network management defined by data rates of up to 10MBps. The Fast SCSI the International Organization for Stan- connector has 50 pins. dardization (ISO) and CCITT. Fault man- See also Fast/Wide SCSI; SCSI-2; Small agement is used in detecting, isolating, and Computer System Interface; Ultra SCSI; correcting faults on the network. Ultra Wide SCSI; Wide SCSI. fault tolerance A design method that en- Fast/Wide SCSI A version of the SCSI-2 sures continued system operation in the interface that can transfer data 16 bits at a event of individual failures by providing re- time at data rates of up to 20MBps. The dundant elements. Fast/Wide SCSI connector has 50 pins. At the component level, the design includes See also Fast SCSI; SCSI-2; Small Comput- redundant chips and circuits and the capa- er System Interface; Ultra SCSI; Ultra Wide bility to bypass faults automatically. At the SCSI; Wide SCSI. computer-system level, any elements that are likely to fail, such as processors and FAT See file allocation table. large disk drives, are replicated. FAT16 In Microsoft Windows, a file Fault-tolerant operations often require allocation table that uses a 16-bit cluster backup or UPS (uninterruptible power 141 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 142 Thursday, May 4, 2000 11:59 AM fax supply) systems in the event of a main The advantages of a fax modem include power failure. In some cases, the entire ease of use and convenience; the main dis- computer system is duplicated in a remote advantage is that the material you want to location to protect against vandalism, acts fax must be present in digital form in the of war, or natural disaster. computer. Unless you have access to a scan- ner, you cannot fax handwritten notes, line See also clustering; data protection; disk art, or certain kinds of graphics. Most faxes duplexing; disk mirroring; redundant ar- sent directly from a PC using a fax modem ray of inexpensive disks; System Fault are text files. Tolerance. fax server A dedicated server that pro- fax Short for facsimile. The electronic vides fax sending and receiving services to transmission of copies of documents for re- users on the network. production at a remote location. The term FCC See Federal Communications fax can be used as a verb for the process and Commission. as a noun for the machine that does the work and also for the item that is actually FCC certification Approval by the FCC transmitted. (Federal Communications Commission) that a specific computer model meets its The sending fax machine scans a paper im- standards for radio frequency interference age and converts the image into a form suit- (RFI) emissions. There are two levels of able for transmission over a telephone line. certification: The receiving fax machine decodes and prints a copy of the original image. Each fax I Class A certification, which is for comput- machine includes a scanner, modem, and ers used in commercial settings, such as printer. mainframes and minicomputers Originally, facsimile machines were rotat- I The more stringent Class B certification, which is for computers used in the home ing drums (CCITT Groups 1 and 2); then and in home offices, such as PCs, laptops, came modems (CCITT Group 3), and even- and portables tually they will be completely digital (CCITT Group 4). See also extremely low-frequency emis- sion; radio frequency interference; very See also CCITT Groups 1–4; fax modem. low-frequency emission. fax board See fax modem. FDDI See Fiber Distributed Data Interface. fax modem An adapter that fits into a PC expansion slot providing many of the FDDI-II A variation of the Fiber Distrib- capabilities of a full-sized fax machine, but uted Data Interface standard. The FDDI-II at a fraction of the cost. Some external mo- version is designed for networks transmit- dems also have fax capabilities. ting real-time full-motion video (or other 142 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 143 Thursday, May 4, 2000 11:59 AM Fiber Distributed Data Interface information that cannot tolerate any de- television, all interstate telecommunica- lays) and requires that all nodes on the net- tions services, and all international servic- work use FDDI-II; otherwise, the network es that originate inside the United States. automatically reverts to FDDI. All computer equipment must be certified FDDI-II divides the bandwidth into 16 ded- by the FCC before it can be offered for sale icated circuits operating at from 6.144Mbps in the United States. The certification en- to a maximum of 99.072Mbps. Each of sures that the equipment meets the legal these channels can be further subdivided for limits for conductive and radio frequency a total of 96 separate 64Kbps circuits. interference, which could otherwise inter- fere with commercial broadcasts. FDDI-II is not widely used because it is in- compatible with FDDI and because Fast For more information on the FCC, see Ethernet and Asynchronous Transfer Mode www.fcc.gov. (ATM) both provide better solutions. See also FCC certification. FDM See frequency-division female connector Any cable connector multiplexing. with receptacles designed to receive the pins FDX See full-duplex. on the male connector. See also male connector. Federal Communications Commission Abbreviated FCC. A U.S. government regulatory body for radio, FEMALE CONNECTOR FEXT See far-end crosstalk. FDDI’s 100Mbps speed is close to the inter- nal speed of most computers, which makes it FF See form feed. a good choice to serve as a super backbone Fiber Distributed Data Interface Ab- for linking two or more LANs or as a fiber- breviated FDDI. The ANSI X3T9.5 specifi- optic bus connecting high-performance cation for fiber-optic networks transmitting engineering workstations. FDDI is suited to at a speed of up to 100Mbps over a dual, systems that require the transfer of large counter rotating, token-ring topology. amounts of information, such as medical 143 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 144 Thursday, May 4, 2000 11:59 AM fiber-optic cable imaging, three-dimensional seismic process- tions up to 2 kilometers (1.25 miles) apart; ing, and oil reservoir simulation. The FDDI- with single-mode fiber, run length increases II version of the standard is designed for net- up to 60 kilometers (37.2 miles) between works transmitting real-time full-motion vid- stations. This type of network can also run eo (or other information that cannot tolerate over shielded and unshielded twisted-pair any delays) and requires that all nodes on the cabling (when it is known as CDDI, or Cop- network use FDDI-II; otherwise, the network per Distributed Data Interface) for shorter automatically reverts to FDDI. distances. See also FDDI-II. A FDDI network using multimode fiber- optic cable can include as many as 500 sta- FIBER DISTRIBUTED DATA INTERFACE fiber-optic cable A transmission tech- to electrical interference, offers better se- nology that sends pulses of light along spe- curity, and has better signal-transmitting cially manufactured optical fibers. qualities. However, it is more expensive than traditional cables and is more diffi- Each fiber consists of a core, thinner than a cult to repair. Fiber-optic cable is often human hair, surrounded by a sheath with a used for high-speed backbones, but as much lower refractive index. Light signals prices drop, we may even see fiber-optic introduced at one end of the cable are con- cable running to the desktop. ducted along the cable as the signals are re- flected from the sheath. See also multimode fiber; single-mode fiber. Fiber-optic cable is lighter and smaller than traditional copper cable, is immune 144 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 145 Thursday, May 4, 2000 11:59 AM file allocation table FIBER-OPTIC CABLE Fibre Channel An interconnection stan- A file can contain a program or part of a dard designed to connect peripherals, mass program, just data, or a user-created docu- storage systems, archiving and imaging sys- ment. Files may actually be fragmented or tems, and engineering workstations. stored in many different places across the disk. The operating system manages the Fibre Channel provides bandwidth from task of locating all the pieces when a request 100Mbps to 800Mbps over a variety of ca- is made to read the file. ble types, including multimode fiber, coax- ial cable, and shielded twisted-pair. file allocation table Abbreviated FAT, pronounced “fat.” A table, maintained by The Fibre Channel Interconnect Stan- the operating systems, that lists all the dard was developed by the American Na- blocks of disk space available on a disk. tional Standards Institute (ANSI) X3T9 committee. The FAT includes the location of each block, as well as whether it is in use, avail- file A named collection of information able for use, or damaged in some way and that appears to the user as a single entity therefore unavailable. Because files are not and is stored on disk. necessarily stored in consecutive blocks on 145 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 146 Thursday, May 4, 2000 11:59 AM file compression a disk, the FAT also keeps track of which Norton Utilities from Symantec, also con- pieces belong to which file. tain file-compression programs. See also FAT16; FAT32; file fragmentation. file-conversion program An applica- tion that converts a file from one format to file compression A technique that another without altering the contents of the shrinks program or data files so that they file. occupy less disk space. The file must then be The conversion may be between the formats extracted or decompressed before use. of two applications that use the same oper- Some types of files, such as word processor ating system (such as between two different documents, can be compressed by 50 per- Microsoft Windows word processors) or be- cent or more. Recompressing an already tween the formats of applications from dif- compressed file usually makes the file ferent operating systems. Applications are slightly larger because of the compression also available that convert a graphical image overhead. from one file format to another. File compression can be automatic and Many of the applications that change a performed by the operating system, or it Macintosh file into a PC-compatible file, or can be manual and performed by a file- vice versa, consist of two programs running compression program. simultaneously on two physically connect- See also file-compression program. ed computers. MacLink Plus from Data Viz and LapLink Mac from Traveling Software file-compression program An applica- are two examples of this type of file-conver- tion that compresses files so that they take sion program. up less space on the disk. Some file-com- file format A file structure that defines pression programs are individual, stand- the way information is stored in the file and alone applications; others are built into the how the file appears on the screen or on the operating system. printer. Individual file-compression programs can The simplest file format is a plain ASCII file. compress one or more files at a time. The Some of the more complex formats are utilities PKZIP and WinZip (for Microsoft DCA (Document Content Architecture) Windows) and StuffIt (for the Macintosh) and RTF (Rich Text Format), which in- operate that way. When compression is clude control information for use by a built into the operating system, it usually printer; TIFF (Tagged Image File Format) compresses all the files on a specific disk, and EPS (Encapsulated PostScript), which disk partition, or volume. hold graphics information; and DBF Many of the stand-alone file-compression (Xbase database file) and DB (Paradox file), programs, such as PKZIP, LHArc, and which are database formats. Word process- StuffIt, are available as shareware, and ing programs, such as Microsoft Word, also many popular utility packages, such as the create files in special formats. 146 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 147 Thursday, May 4, 2000 11:59 AM file permissions file fragmentation Storage of files in In MS-DOS, file and directory names have pieces scattered on a disk. As files grow on two parts. They can have up to eight char- a hard disk, they can be divided into sev- acters in the name and up to three charac- eral small pieces. By fragmenting files, the ters in the optional filename extension, operating system makes reasonable use of separated from the name by a period. Many the disk space available. The problem with applications take over the extension part of file fragmentation is that the disk heads the filename, using specific groups of char- must move to different locations on the acters to designate a particular file type. disk to read or write to a fragmented file. In the Macintosh operating system, filenames This process takes more time than reading can be up to 32 characters and can contain the file as a single piece. To speed up file any character except a colon (:), which is used operations, you can use a disk optimizer or to separate elements of a path name. defragmenter. Microsoft Windows allows 255-character See also FAT16; FAT32; defragmenter. filenames including spaces, but the name cannot include any of the following charac- file indexing A technique used in Novell ters: / : * ? ” < > |. NetWare to speed up accesses to large files by indexing file allocation table (FAT) filename extension In the MS-DOS file entries. allocation table (FAT) file system, an op- tional three-character suffix added to the file-infecting virus Any virus that in- end of a filename and separated from the fects files on disk, usually executable files name by a period. with filename extensions of .COM, .EXE, and .OVL. An unexpected change in the file file permissions A set of permissions as- size may indicate an infection. In certain sociated with a file (or a directory) that cases, the original program is replaced with specifies who can access the file and in what a new file containing an infected program. way. There are three basic permissions: See also antivirus program; boot sector vi- I Read permission lets you read files. rus; infection; macro virus; multipart virus; polymorphic virus; stealth virus; Trojan I Write permission lets you write (or over- Horse; vaccine; virus. write) files. I Execute permission lets you execute files. file locking See file and record locking. Additional file permissions vary according filename The name of a file on a disk to the operating system in use and the secu- used so that both you and the operating sys- rity system in place. For example, Novell tem can find the file again. Every file in a di- NetWare has the following file permissions: rectory must have a unique name, but files Access Control, Create, Erase, File Scan, in different directories can share the same Modify, Read, Supervisor, and Write. Mi- name. crosoft Windows 2000 has Add and Read, 147 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 148 Thursday, May 4, 2000 11:59 AM File and Print Services for NetWare Change Permissions, Delete, Full Control, file recovery The process of recovering No Access, and Take Ownership. deleted or damaged files from a disk. A file See also rights. can be deleted accidentally or can become inaccessible when part of the file’s control File and Print Services for NetWare information is lost. In many operating sys- An add-on product for Microsoft Windows tems, a deleted file still exists on disk until 2000 that allows Novell NetWare clients to the space it occupies is overwritten with access Windows servers as though they something else or until the file is purged. were NetWare servers. See also undelete. FILER A Novell NetWare workstation File Replication Service In Microsoft utility used to manage the NetWare file sys- Windows 2000 Server, the replacement for tem. Almost any task related to the file sys- Windows NT Directory Replication. tem can be performed using FILER. Admin- istrators can view information about files, File Replication Service log In Mi- directories, and volumes; modify and view crosoft Windows 2000 Server, a special log attributes, rights, and trustee assignments that records any events associated with do- for files and directories; search for files and main controller updates. directories; copy files; and recover and purge See also Directory Service log; DNS Server deleted files. In NetWare 3.x, these last two log; Event Viewer; File Replication Service. functions are found in the SALVAGE and PURGE commands. file server A networked computer used file and record locking A method of to store files for access by other client com- controlling file access in a multiuser envi- puters on the network. ronment, where there is always a possibility On larger networks, the file server runs a that two users will attempt to update the special network operating system. On same file at the same time but with different smaller installations, the file server may run information. The first user to access the file a PC operating system supplemented by locks out all the other users, preventing peer-to-peer networking software. them from opening the file. After the file is See also client; server. updated and closed again, the next user can gain access. file sharing The sharing of files over a File locking is a simple way to prevent simul- network or between several applications taneous updates, but it can seriously degrade running on the same workstation. system performance if many users attempt to Shared files can be read, reviewed, and up- access the same files time after time. To pre- dated by more than one individual. Access to vent this slowdown, many database man- the file or files is often regulated by password agement systems use record locking instead. protection, account or security clearance, or Record locking limits access to individual file locking to prevent simultaneous changes records within the database file. by multiple users. 148 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 149 Thursday, May 4, 2000 11:59 AM finger See also file and record locking. See also file-conversion program; File Transfer Protocol; Kermit; Xmodem; Ymo- filespec A contraction of file specifica- dem; Zmodem. tion, commonly used to denote the com- plete drive letter, path name, directory File Transfer Protocol Abbreviated name, and filename needed to access a spe- FTP. The TCP/IP Internet protocol used cific file. when transferring single or multiple files from one computer system to another. file system In an operating system, the structure by which files are organized, FTP uses a client/server model, in which a stored, and named. small client program runs on your comput- er and accesses a larger FTP server running Some file systems are built-in components of on an Internet host. FTP provides all the the operating system; others are installable. tools needed to look at directories and For example, OS/2, Unix, and Microsoft files, change to other directories, and Windows are all capable of supporting sev- transfer text and binary files from one sys- eral different file systems at the same time. tem to another. Other, installable file systems provide sup- port for specific devices such as CD-ROM or See also anonymous FTP; ftp; Telnet. DVD. FILTCFG A Novell NetWare 4.x Net- File Transfer Access and Manage- Ware Loadable Module (NLM) that allows ment Abbreviated FTAM. The Open you to set up and configure filters for Inter- Systems Interconnect (OSI) protocol for network Packet eXchange (IPX), TCP/IP, transferring and remotely accessing files on and AppleTalk protocols. Filters help to different makes and models of computers control the type and amount of information that are also using FTAM. sent to and received by a router, to limit file-transfer program An application traffic to certain segments of the network, used to move a file from a computer of one and to provide security. type to a computer of another type. The file filtering 1. The mechanism that prevents format itself may also be changed during certain source and destination addresses this transfer. from crossing a bridge or router onto an- Many of the applications that change a other part of the network. Macintosh file into a PC-compatible file, or 2. The process of automatically selecting vice versa, consist of two programs running specific frequencies and discarding others. simultaneously on two physically connect- ed computers. MacLink Plus from Data Viz finger A utility found on many Internet and LapLink Mac from Traveling Software systems that displays information about a are two file-transfer programs that also of- specific user, including full name, logon fer a wide variety of popular file-format time, and location. Originated in the Unix conversions. world. 149 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 150 Thursday, May 4, 2000 11:59 AM FIRE PHASERS The finger utility may also display the con- first-layer domain In Microsoft Win- tents of the user’s .plan or .profile file, and dows 2000 Server, a Windows 2000 do- there are those who exploit this in novel main whose parent domain is the root ways to display such varied information as domain. instructions for using a university’s Coke- See also domain; parent domain. vending machine, posting sports scores, and listing earthquake activity. flame A deliberately insulting e-mail message or post to a Usenet newsgroup, of- FIRE PHASERS A Novell NetWare login ten containing a personal attack on the script command that makes a noise using writer of an earlier post. the workstation’s speaker. See also flame bait; flame war. The sound is supposed to resemble the phasers on the USS Enterprise. With fire flame bait An insulting or outrageous phasers, you can have the computer emit up e-mail post to a Usenet newsgroup specifically to nine sounds or blasts. designed to provoke other users into flaming the originator. firewall A barrier established in hard- See also flame; flame war. ware or in software, or sometimes in both, that monitors and controls the flow of traf- flame war In a Usenet newsgroup, a pro- fic between two networks, usually a private longed series of flames, which may have be- LAN and the Internet. gun as a creative exchange of views but A firewall provides a single point of entry which quickly descended into personal at- where security can be concentrated. It al- tacks and crude name-calling. lows access to the Internet from within the See also flame bait. organization and provides tightly con- trolled access from the Internet to resources flash memory A special form of ROM on the organization’s internal network. that can be erased at signal levels commonly found inside the PC. See also application-level filter; dual- homed host; Intrusion Detection System; This ability allows the contents to be repro- packet-level filter; proxy server; stateless grammed without removing the chips from filter. the computer. Also, once flash memory has been programmed, you can remove the ex- FireWire See 1394. pansion board it is mounted on and plug it into another computer without loss of the firmware Any software stored in a form new information. of read-only memory (ROM), erasable pro- See also PC Card. grammable read-only memory (EPROM), or electrically erasable programmable read- flavor A slang expression meaning type only memory (EEPROM) that maintains its or kind, as in “Unix comes in a variety of contents when power is removed. flavors.” 150 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 151 Thursday, May 4, 2000 11:59 AM forest floating-point processor A special- that other readers are reminded of the dis- purpose, secondary processor designed to cussion so far, and this quoted part of the perform floating-point calculations much post is usually indicated by greater than faster than the main processor. symbols (>). If you do quote from a previ- Many processors, such as the Intel 80386, ous post, only quote the minimum amount had matched companion floating-point to get your point across; never quote the processors. However, the current trend in whole message as this is considered a waste processor design is to integrate the floating- of time and resources. point unit into the main processor, as in the See also thread. Intel Pentium. footprint The amount of desktop space flooding A denial of service attack in or floor space occupied by a computer, which a huge number of nuisance connec- printer, or monitor. tion attempts are made in order to consume all the available processing time. forced perfect termination A tech- See also brute-force attack; denial of ser- nique used to terminate a Small Computer vice attack; dictionary attack; social engi- System Interface (SCSI). Forced perfect ter- neering; Trojan Horse. mination actively monitors the bus to en- sure that no signal reflection occurs. flow control 1. In communications, See also active termination; passive control of the rate at which information is termination. exchanged between two computers over a transmission channel. Flow control is need- foreground In an operating system, a ed when one of the devices cannot receive process that runs in the foreground is run- the information at the same rate as it can be ning at a higher level of priority than is a sent, usually because some processing is re- background task. quired on the receiving end before the next transmission unit can be accepted. Flow Only multitasking operating systems control can be implemented either in hard- support true foreground and background ware or in software. processing; however, some application 2. In networking, control of the flow of programs can mimic it. For example, many data throughout the network, ensuring that word processors will print a document network segments are not congested. A while still accepting input from the router controls data flow by routing around keyboard. any trouble spots. See also background. See also handshaking. forest In Microsoft Windows 2000, a followup A reply to a post in a Usenet collection of Active Directory trees that do newsgroup or to an e-mail message. A fol- not share a contiguous namespace, but do lowup post may quote the original post so share a common schema and global catalog. 151 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 152 Thursday, May 4, 2000 11:59 AM formatting For example, if acme.com and widget.com FQDN See fully qualified domain name. were linked via a trust relationship but shared a common schema and global cata- fractional T1 One portion of a T1 circuit. log, they would be considered a forest; in A T1 circuit has a capacity of 1.544Mbps, other words, a forest is a group of trees that the equivalent of twenty-four 64Kbps chan- trust each other. nels. Customers can lease as many of these 64Kbps channels as they need; they are not See also Active Directory; Global Catalog; required to lease the entire 1.544Mbps schema; tree. circuit. formatting The process of initializing a fragmentation See file fragmentation. new, blank floppy disk or hard disk so that it can be used to store information. frame 1. A block of data suitable for transmission as a single unit; also referred form feed Abbreviated FF. A printer to as a packet or a block. Some media can command that advances the paper in the support multiple frame formats. printer to the top of the next page. The Form Feed button on the printer also per- 2. In digital video, one screen of informa- forms this same function. An application tion, including both text and graphics. can also issue the command. In the ASCII See also frames per second. character set, a form feed has the decimal value of 12. frame relay A CCITT standard for a forward error correction A technique packet-switching protocol, running at used to control errors that insert extra or re- speeds of up to 2Mbps, that also provides dundant bits into the data stream. The re- for bandwidth on demand. Frame relay is ceiving device uses the redundant bits to less robust than X.25 but provides better ef- detect and, if possible, correct the errors in ficiency and higher throughput. the data. Frame relay is available from many compa- See also error detection and correction. nies, including AT&T, CompuServe, Sprint, WilTel, and the Bell companies. forwarding The process of passing data See also Asynchronous Transfer Mode. on to an intermediate or final destination. Forwarding takes place in network bridges, frames per second Abbreviated fps. routers, and gateways. The number of video frames displayed each four-wire circuit A transmission system second. Although 24fps is considered the in which two half-duplex circuits, consist- slowest frame rate that provides convincing ing of two wires each, are combined to cre- motion to the human eye, most Internet vid- ate one full-duplex circuit. eo runs at between 5 and 15fps. To main- tain a 15fps rate, you need a fast Pentium- fps See frames per second. based system with a 56Kbps modem. 152 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 153 Thursday, May 4, 2000 11:59 AM frequency-division multiplexing framing The process of dividing data for source code should always accompany the transmission into groups of bits and adding software. The theory being, that if you a header as well as a checksum to form a make a modification or fix an error, the frame. In asynchronous communications, change can be sent out to all the other users, framing is the process of inserting start bits saving time and preventing duplication of and stop bits before and after the data to be effort. transmitted. Also, any software developed under the FSF FreeBSD A free implementation of Unix General Public License (GPL) must also be for the Intel family of processors, derived covered by the same terms of the GPL; in from the 4.4BSD Lite releases. other words, you cannot use the free soft- The distribution is free, but there may be a ware to develop a commercial product for small charge to cover the distribution media sale. and packaging. FreeBSD also includes For more information on the Free Software XFree86, a port of the X Window system to Foundation, see www.gnu.org/fsf. the Intel processors. See also copy left; FreeBSD; freeware; Most of FreeBSD is covered by a license GNU; open source software. that allows redistribution as long as the code acknowledges the copyright of the freeware A form of software distribu- Regents of the University of California and tion in which the author retains copyright the FreeBSD Project. Those parts of Free- to the software, but makes the program BSD that include GNU software are cov- available to others at no cost. The program ered separately by the Free Software Foun- cannot be resold by a third party for profit. dation license. See also copy left; Free Software Founda- See also copy left; Free Software Founda- tion; freeware; GNU; Linux; open source tion; GNU; open source software. software. frequency-division multiplexing Ab- free memory Any area of memory not breviated FDM. A method of sharing a currently in use. Often refers to the memory transmission channel by dividing the band- space remaining for applications to use af- width into several parallel paths, defined ter the operating system and the system de- and separated by guard bands of different vice drivers have been loaded. frequencies designed to minimize interfer- ence. All signals are carried simultaneously. Free Software Foundation Abbreviat- ed FSF. An organization founded by Rich- FDM is used in analog transmissions, such ard Stallman that develops the freely as in communications over a telephone line. available GNU software. See also inverse multiplexing; statistical The FSF philosophy is that all software multiplexing; time-division multiplexing; should be free for everyone to use and that wavelength division multiplexing. 153 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 154 Thursday, May 4, 2000 11:59 AM frequently asked questions frequently asked questions Abbrevi- Frye Utilities A package of network man- ated FAQ, pronounced “fack.” A docu- agement utilities from Frye Computer Sys- ment that contains answers to questions tems that includes hardware and software that new users often ask when they first inventory, NetWare server monitoring, traf- subscribe to a newsgroup or first access a fic monitoring, application metering, and Web site. software distribution. The FAQ contains answers to common FSF See Free Software Foundation. questions that the seasoned users have FTAM See File Transfer Access and grown tired of answering. New users Management. should look for and read the FAQ before posting their question, just in case the FAQ FTP See File Transfer Protocol. contains the answer. ftp A command used to transfer files to fried A slang expression for burned-out and from remote computers using the File hardware, especially hardware that has suf- Transfer Protocol. You can use ftp to log on fered from a power surge. Also applied to to an Internet computer and transfer text and binary files. people, as in “My brain is fried; I haven’t slept since last weekend.” When you use ftp, you start a client pro- gram on your computer that connects to a front-end application An application server program on the Internet computer. running on a networked workstation that The commands that you give to ftp are works in conjunction with a back-end sys- translated into instructions that the server tem running on the server. Examples are e- program executes for you. mail and database programs. The original ftp program started life as a See also client/server architecture. Unix utility, but versions are now available for all popular operating systems; ftp is also front-end processor A specialized pro- built into all the major Web browsers. cessor that manipulates data before passing See also anonymous ftp; File Transfer it on to the main processor. Protocol. In large computer-to-computer communi- full backup A backup that includes all cations systems, a front-end processor is files on a hard disk or set of hard disks. A often used to manage all aspects of com- network administrator must decide how of- munications, leaving the main computer ten to perform a full backup, balancing the free to handle the data processing. need for security against the time taken for See also back-end processor. the backup. See also differential backup; incremental FRS See File Replication Service. backup. 154 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 155 Thursday, May 4, 2000 11:59 AM function keys full-duplex Abbreviated FDX. The capa- the fully qualified domain name becomes bility for simultaneous transmission in two wallaby.my-company.com. directions so that devices can be sending See also Domain Name Service. and receiving data at the same time. See also four-wire circuit; half-duplex. function keys The set of programmable keys on the keyboard that can perform full-page display Any monitor capable special tasks assigned by the current of displaying a whole page of text. Full- application. page displays are useful for graphical art Most keyboards have 10 or 12 function and desktop publishing applications, as keys (F1 to F10 or F1 to F12), some of well as medical applications. which are used by an application as short- fully qualified domain name A host cut keys. For example, many programs use name with the appropriate domain name ap- F1 to gain access to the Help system. In pended. For example, on a host with the host some programs, the use of function keys is name wallaby and the Domain Name Ser- so complex that special plastic key overlays vice (DNS) domain name my-company.com, are provided as guides for users. 155 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 156 Thursday, May 4, 2000 11:59 AM G G G Abbreviation for giga-, meaning 1 bil- Gateway, Inc. A leading direct-marketer lion, or 109. of PCs, servers, and related peripherals, originally known as Gateway 2000. Also See also gigabyte. an ISP offering Internet access through gateway.net. Gartner Group, Inc. An independent research organization for the computer For more information on Gateway, Inc., see hardware, software, communications, and www.gateway.com. related industries. gateway server A communications server that provides access between net- Gartner Group first developed the concept works that use different access protocols. of total cost of ownership (TCO) and now provides TCO software tools since the ac- Gateway Services for NetWare A Mi- quisition of Interpose. Gartner Group also crosoft Windows NT Server service that al- owns Datapro Information Services and the lows an NT server to act as a gateway to a market analysis company Dataquest. NetWare network. NT clients can access a NetWare server using the same methods For more information on Gartner Group, used to access an NT server. see www.gartner.com. gauge A measurement of the physical See also total cost of ownership. size of a cable. Under the American Wire Gauge (AWG) standards, higher numbers gate array See application-specific indicate thinner cable. integrated circuit. See also cabling standards. gateway A shared connection between a GB See gigabyte. LAN and a larger system, such as a main- frame computer or a large packet-switching Gb See gigabit. network, whose communications protocols Gbit See gigabit. are different. Usually slower than a bridge or router, a gateway is a combination of GDS See Global Directory Service. hardware and software with its own pro- gender changer A special intermediary cessor and memory used to perform proto- connector for use with two cables that both col conversions. have only male connectors or only female See also bridge; brouter; router. connectors. 156 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 157 Thursday, May 4, 2000 11:59 AM global account GENDER CHANGER geostationary Also known as geosyn- Gigabit Ethernet A 1Gbps (1,000Mbps) chronous. The type of orbit required to extension of the IEEE 802.3 Ethernet stan- keep a communications satellite in a fixed dard, known as 1000Base-X. position relative to the earth. This standard has been developed by the The satellites angular rate and direction of IEEE 802.3z Task Group and a number of rotation are matched to those of the earth, interested companies collectively known as and the satellite orbits the earth every 24 the Gigabit Ethernet Alliance. Gigabit hours at about 36,000 kilometers (22,350 Ethernet runs over multimode fiber-optic miles). Three satellites in geostationary or- cable and is intended for use as a backbone bit can cover 95 percent of the earths sur- and a way to connect high-speed routers, face (the remaining 5 percent is above the switches, and hubs. Arctic Circle). See also Ethernet; Fast Ethernet. geosynchronous See geostationary. GIF See Graphics Interchange Format. gigabyte Abbreviated GB. Strictly speaking, one billion bytes; however, in giga- A prefix meaning 1 billion, or 109. computing, in which bytes are most often See also gigabyte. counted in powers of 2, a gigabyte becomes 230, or 1,073,741,824 bytes. gigabit Abbreviated Gbit and Gb. Usu- ally 1,073,824 binary digits or bits of data. global account In Microsoft Windows Sometimes used as equivalent to one bil- NT Server, a user or group account defined lion bits. on a primary domain controller that can be See also kilobit; megabit. used from all the computers in the domain. 157 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 158 Thursday, May 4, 2000 11:59 AM Global Catalog Global Catalog In Microsoft Active Di- global login A mechanism that permits rectory, the storage of selected properties users to log on to the network, rather than for all the objects in the Active Directory. repeatedly logging on to individual servers. A global logon can provide access to all net- The Global Catalog allows users in an or- work resources. ganization with multiple sites to locate re- sources quickly, without having to cross globally unique identifier Abbreviated WAN links. In this way, users can examine GUID. In Microsoft Active Directory, a a local source to find the location of a net- unique 128-bit number that identifies an work resource. Active Directory object. See also Active Directory; forest; tree. See also Active Directory. Global Directory Service Abbreviated global network An international net- GDS. An implementation of the X.500 di- work that spans all departments, offices, rectory service for managing remote users and subsidiaries of the corporation. and addresses. Global networks bring their own set of See also X.500. problems, including those of different time zones, languages, established standards, global directory services Directory and PTT (Postal Telephone and Telegraph) services that view the entire network as a companies. single entity. A global directory system al- GNU Pronounced “ga-noo.” A Free Soft- lows the network administrator to define ware Foundation (FSF) project devoted to all network resources—users, printers, and developing a complete, freely available servers—at one time. Unix system that contains no AT&T code. Banyans StreetTalk and Novells NetWare The name GNU is a recursive acronym for Directory Services (NDS) are examples of “GNU’s not Unix!” global directory services. Many of the tools and utilities developed See also domain directory services. for this project have been released and are very popular with users of 4.4BSD, Free- global group In Microsoft Windows NT BSD, and Linux. Server, user accounts granted server and For more information on GNU, see workstation rights in their own and other www.gnu.org. domains whose security systems allow ac- See also 4.4BSD Lite; FreeBSD; Hurd; cess. Global groups are a means of provid- Linux; open source software. ing rights and permissions to resources inside and outside the domain to a group of Gopher A client/server application that users within a single domain. presents Internet text resources as a series See also local group. of menus, shielding the user from the 158 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 159 Thursday, May 4, 2000 11:59 AM graphics accelerator board underlying mechanical details of IP changing it. You can set the number of addresses and different access methods. grace logons a user is allowed. Gopher menus may contain documents you graphical user interface Abbreviated can view or download, searches you can GUI, pronounced “gooey.” A graphics- perform, or additional menu selections. based user interface that allows users to se- When you choose one of these items, Go- lect files, programs, and commands by pher does whatever is necessary to obtain pointing to pictorial representations on the the resource you requested, either by down- screen rather than by typing long, complex loading a document or by jumping to the se- commands from a command prompt. lected Gopher server and presenting its top- Applications execute in windows, using a level menu. consistent set of drop-down menus, dialog Gopher clients are available for most pop- boxes, and other graphical elements, such ular operating systems, including the Mac- as scroll bars and icons. This consistency intosh, MS-DOS, Windows, and Unix. among interface elements is a major benefit for the user, because as soon as you learn See also Gopherspace; World Wide Web. how to use the interface in one program, you can use it in all other programs running Gopherspace A collective term used to in the same environment. describe all the Internet resources accessible using Gopher. Gopher is so good at hiding The use of graphical elements in a user in- the mechanical details of the Internet that terface was pioneered at Xerox Corpora- this term was coined to represent all the re- tions Palo Alto Research Center (PARC) in sources reachable using Gopher. the early 1970s. Unfortunately, at that time the hardware needed to support such a user GOSIP Acronym formed from Govern- interface was well beyond the reach of most ment Open System Interconnection Profile. users. In 1979, Steve Jobs of Apple Com- A suite of standards intended for use in gov- puter visited PARC and recognized the im- ernment projects and based on the Open portance of the user-interface work being Systems Interconnect (OSI) reference mod- done; this visit led to the development of the el. Some measure of GOSIP compliance is interface for the ill-fated Apple Lisa com- required for government networking pur- puter, and eventually to the Apple Macin- chases. GOSIPs exist in many countries, tosh series of computers. Since then, GUIs including the United States, Canada, have been developed for most computing France, Germany, Australia, and the Unit- environments. ed Kingdom. graphics accelerator board A special- GPO See group policy object. ized expansion board containing a graphics coprocessor as well as all the other circuitry grace login Allows a user to finish log- found on a video adapter. Sometimes called ging on using an expired password without a video accelerator board. 159 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 160 Thursday, May 4, 2000 11:59 AM graphics coprocessor Transferring most of the graphics process- group account An account containing ing tasks from the main processor to the other member accounts. All the rights and graphics accelerator board improves sys- permissions accorded to the group are also tem performance considerably, particularly granted to the group members, making for Microsoft Windows users. group accounts a convenient way to pro- vide a common set of capabilities to collec- graphics coprocessor A fixed-function tions of user accounts. graphics chip, designed to speed up the processing and display of high-resolution group identifiers Security identifiers images. Popular coprocessors include S3 containing the set of permissions granted to Inc’s 86C911 and Weitek’s W5086 and the group. If a user account is part of a W5186. group, the group identifier is appended to that user’s security identifier, granting the Graphics Interchange Format Abbre- user all the permissions granted to that viated GIF; pronounced “gif.” A graphics group. file format, originating on CompuServe, that results in relatively small graphics files. See also security identifier. An image may contain as many as 256 col- Group object In Novell NetWare Direc- ors, including a transparent color, and a tory Services (NDS), an object that contains lossless compression method reduces the a list of user object names. size of the file. A graphic in this format can be used as an inline image on a Web page. See also leaf object; NetWare Directory Services. A revision of this format, known as GIF89a, adds animation features, transpar- group policy In Microsoft Windows ent backgrounds, and image interleaving. 2000 Server, a central point of administra- See also lossless compression; Joint tion, allowing administrators to install soft- Photographic Experts Group. ware and apply standard settings to multiple users and computers throughout graphics mode A video adapter mode in an organization. which everything displayed on the screen is created pixel by pixel. Text mode, by con- group policy object Abbreviated GPO. trast, uses ready-made characters from a In Microsoft Windows 2000 Server, a col- built-in character set. lection of group policy settings defined at the local machine, site, domain, or organi- grayed command See dimmed com- zational unit level. mand. groupware Network software designed group A collection of network users for use by a group of people all working on who all have the same level of security and the same project or who need access to the can all be managed collectively. same data. 160 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 161 Thursday, May 4, 2000 11:59 AM guru See also Lotus Notes; workflow software; Allowing people to use the guest account workgroup. may breach company security policies. guard band A small-frequency band GUI See graphical user interface. used to separate multiple bands in a broad- GUID See globally unique identifier. band transmission and prevent interference between the communications channels. guru An operating system expert with a reputation for being helpful to other, less guest account In Microsoft Windows knowledgeable users. 2000, a built-in account available to users who do not have an account on the system. 161 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 162 Thursday, May 4, 2000 11:59 AM H.323 H H.323 A videoconferencing standard de- More recently, in popular culture at large, veloped by the International Telecommu- the term has come to mean a person who nication Union (ITU) that defines video- breaks into other people’s computers with conferencing from the desktop over LANs, malicious intent (what programmers call a intranets, and the Internet. “cracker”). Many countries now treat con- victed crackers in the same way that they H.323 specifies techniques for compressing treat conventional breaking-and-entering and transmitting real-time voice, video, and criminals. data between a pair of videoconferencing workstations. It also describes signaling See also intruder. protocols for managing audio and video streams, as well as procedures for breaking HAL See Hardware Abstraction Layer. data into packets and synchronizing trans- missions across communications channels. half-duplex Abbreviated HDX. In asyn- chronous transmissions, the ability to See also Real-time Transport Protocol; transmit on the same channel in two direc- T.120. tions, but only in one direction at a time. See also communications parameters; du- hack Originally, an expedient, although plex; full-duplex. short-term, solution to a programming problem. This solution often bypassed Hamming code A forward-error correc- some of the more traditional software- tion technique used to detect and correct development processes. Now the word single-bit errors during transmission. hack is often used to describe a well-craft- ed piece of work that produces just what is The Hamming code adds three verification needed; it does not imply malicious intent bits to the end of each four bits of data. The to break into other people’s systems for receiving device performs a similar process gain. to ensure that the four data bits were re- ceived correctly and to detect any missing See also hacker; kluge. bits. hacker In the programming community, See also error detection and correction. where the term originated, this term de- scribes a person who pursues knowledge of hand-held computer A portable com- computer systems for its own sake—some- puter that is small enough to be held in one one willing to “hack through” the steps of hand, such as the enormously popular putting together a working program. PalmPilot from 3Com Corporation. 162 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 163 Thursday, May 4, 2000 11:59 AM hard disk drive handshaking The exchange of control hard disk The part of a hard disk drive codes or particular characters to maintain that stores data, rather than the mechanism and coordinate data flow between two for reading and writing to it. Sometimes devices so that data is only transmitted called a platter. when the receiving device is ready to hard-disk controller An expansion accept the data. board that contains the necessary circuitry Handshaking can be implemented in either to control and coordinate a hard disk drive. hardware or software, and it occurs be- Many hard-disk controllers can manage tween a variety of devices. For example, the more than one hard disk, as well as floppy data flow might be from one computer to disks and tape drives. On some PCs, the another computer or from a computer to a hard-disk controller is built into the mother- peripheral device, such as a modem or a board, and in the case of an Integrated Drive printer. Electronics hard disk, the controlling circuit- See also flow control; XON/XOFF. ry is mounted on the drive itself, eliminating the need for a separate controller. hang 1. When a program waits for an hard disk drive A storage device that event that never occurs, as in “the program uses a set of rotating, magnetically coated hangs waiting for a character from the disks called platters to store data or pro- keyboard.” grams. In everyday use, the terms hard disk, hard disk drive, and hard drive are used in- 2. A slang expression used when attaching terchangeably, because the disk and the a new piece of hardware to a system, usu- drive mechanism are a single unit. ally an external device attached by one or more cables, as in “I’m going to hang a new A typical hard-disk platter rotates at several tape drive on the server this afternoon.” thousand revolutions per minute, and the read/write heads float on a cushion of air See also deadlock. from 10 to 25 millionths of an inch thick so that the heads never come into contact with hard-coded A description of software the recording surface. The whole unit is her- written in a way that does not allow for metically sealed to prevent airborne con- flexibility or future expansion. For exam- taminants from entering and interfering ple, when program variables are placed di- with these close tolerances. rectly in the code rather than supplied as Hard disks range in storage capacity from a input from the user, the entire program few tens of megabytes to several terabytes. must be recompiled to change the value, an The more storage space on the disk, the obvious waste of resources. more important your backup strategy be- See also hard-wired. comes. Hard disks are reliable, but they do 163 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 164 Thursday, May 4, 2000 11:59 AM hard-disk interface fail, and usually at the most inconvenient boards, displays, and printers. If you can moment. stub your toe on it, it must be hardware. See also high-capacity storage system; See also firmware; liveware; software. mini-hard disk; redundant array of inex- pensive disks; single large expensive disk. Hardware Abstraction Layer Abbrevi- ated HAL. The lowest level of the Microsoft hard-disk interface A standard way of Windows NT operating system, which is accessing the data stored on a hard disk. Sev- specifically tailored to the type of hardware eral hard-disk interface standards have used in the server. If the hardware changes, evolved over time, including the ST506 In- changes also have to be made to the HAL. terface, the Enhanced Small Device Interface hardware address The address as- (ESDI), the Integrated Drive Electronics In- signed to a network interface card (NIC) by terface (IDE), and the SCSI (Small Computer the original manufacturer or by the net- System Interface). work administrator if the interface card is See also PC Memory Card International configurable. Association. This address identifies the local device ad- dress to the rest of the network and allows hard-disk type A number stored in a messages to find the correct destination. personal computer’s CMOS random access Also known as the physical address, media memory area that defines certain hard-disk access control (MAC) address, or Ethernet characteristics, such as the number of read/ address. write heads and the number of cylinders on the disk. This number is not directly acces- Hardware Compatibility List Abbrevi- sible from the operating system. Some PCs ated HCL. A list of all the hardware devic- require a special configuration program to es supported by Microsoft Windows NT access the hard-disk type; others permit ac- and Windows 2000. Items on this list have cess via the computer’s built-in ROM BIOS actually been tested and verified to work setup program. properly with Windows. hard reset A system reset made by press- ing the computer’s Reset button or by turn- hardware dependent The requirement ing the power off and then on again. A hard that a specific hardware component be reset is used only when the system has present for a program to work. Hardware- crashed so badly that pressing Ctrl+Alt+Del dependent software is often difficult to to reboot does not work. move or port to another computer. See also hang; deadlock. See also hardware independent. hardware All the physical electronic hardware independent The ability to components of a computer system, includ- produce similar results in a wide variety ing peripheral devices, printed-circuit of environments, without requiring the 164 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 165 Thursday, May 4, 2000 11:59 AM HDLC presence of specific hardware. The Java See also hash function; hash table. programming language and the PostScript page-description language are both exam- hash table A method of representing ples of hardware independence. Java runs data so that it can be found again very on a wide range of computers, from the PC quickly. to a mainframe; PostScript is used by A hash table assigns a special index code to many printer manufacturers. each piece of data, and specially designed See also hardware dependent. software uses this code to locate the data, rather than repeating what might be a very hardware interrupt An interrupt or re- lengthy search each time the data is quest for service generated by a hardware requested. device, such as a keystroke or a tick from See also hash function; hashing. the clock. Because the processor may re- ceive several such signals simultaneously, Hayes-compatible modem Any mo- hardware interrupts are usually assigned a dem that recognizes the commands in the priority level and processed according to industry-standard AT command set, origi- that priority. nally defined by Hayes Microcomputer See also interrupt request; software Products, Inc. interrupt. HBA See host bus adapter. hard-wired Describes a system designed H-channel A set of ISDN Primary Rate in a way that does not allow for flexibility Interface (PRI) services with predefined or future expansion. May also refer to a de- speeds, designed to carry videoconferenc- vice that is connected directly to the net- ing data streams. work, such as a printer. H-channel services are created from multi- See also hard-coded. ple 64Kbps B channels. Three service levels hash function A function that maps a are commonly available: data item to a numeric value by use of a I H0 operating at 384Kbps transformation. A hash function can con- I H11 operating at 1,536Kbps vert a number that has meaning to a user, such as a key or other identifier, into a value I H12 operating at 1,920Kbps for the location of that data in a structure See also Integrated Services Digital Net- such as a table. work; Primary Rate ISDN. See also hashing; hash table. HCL See Hardware Compatibility List. hashing The process of creating or re- HCSS See high-capacity storage creating a hash table by recalculating the system. search index code assigned to each piece of data in the table. HDLC See High-level Data Link Control. 165 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 166 Thursday, May 4, 2000 11:59 AM HDSL HDSL See High-Bit-Rate Digital Sub- helper A program launched or used by a scriber Line. Web browser to process a file type that the browser cannot handle. Sometimes called a HDX See half-duplex. plug-in. header Information placed at the begin- A helper may view an image, play a sound ning of a file, a data transmission, or an file, or expand a compressed file. A helper archive. that deals with video, graphics, or anima- tion is called a viewer; a helper that deals In an e-mail message, the header contains with sound files is called a player. information about the message, including sender and recipient information, and in- See also player; viewer; Web browser. formation about the route the message took as it was being delivered. hertz Abbreviated Hz. A unit of frequen- cy measurement; 1 hertz equals one cycle In a data transmission, the header may con- per second. tain source and destination address infor- mation, as well as other control data. See also megahertz. In an archive, the header is a block that con- heterogeneous network A network tains information describing the contents of that consists of workstations, servers, net- the archive. work interface cards, operating systems, and Header Error Control In an Asynchro- applications from many vendors, all work- nous Transfer Mode (ATM) cell header, an ing together as a single unit. The network 8-bit field used for detecting errors and cor- may also use different media and different recting single-bit errors. protocols over different network links. See also Asynchronous Transfer Mode. See also enterprise network; homoge- neous network. headless server A server computer with no monitor attached. Hewlett-Packard Company Abbreviat- ed HP. A major manufacturer of hand-held heartbeat An Ethernet signal quality test calculators, personal computers, servers, function. This signal proves that a compo- minicomputers, mainframes, scientific and nent is working and can detect collisions. medical equipment, test and measurement Also known as signal quality error (SQE). equipment, laser and ink jet printers, plot- ters, and software. HEC See Header Error Control. Founded by William Hewlett and David Hello protocol In Asynchronous Trans- Packard in 1939 in a garage, the company fer Mode (ATM), a link state protocol used is now headquartered in Palo Alto, Califor- by nodes to determine who and where their nia. HP has a widely diversified product line neighbors are. of more than 10,000 items, and it has a 166 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 167 Thursday, May 4, 2000 11:59 AM High-Bit-Rate Digital Subscriber Line well-earned reputation for building rugged Hierarchical File System Abbreviated and reliable equipment. HFS. A tree-structured file system used on For more information on Hewlett-Packard, the Macintosh; designed for use with hard see www.hp.com. disks. hex See hexadecimal. Hierarchical Storage Management Abbreviated HSM. A combination of sev- hexadecimal Abbreviated hex. The eral types of file-storage systems, managed base-16 numbering system that uses the by intelligent software. digits 0 through 9, followed by the letters A In HSM, data is moved from one type of through F, which are equivalent to the dec- storage to another depending on how fre- imal numbers 10 through 15. quently the data is accessed. Active data is Hex is a convenient way to represent the bi- held on hard disks, less frequently used data nary numbers that computers use internally is held in near-line storage such as an opti- because it fits neatly into the 8-bit byte. All cal disk system, and data used only infre- the 16 hex digits 0 through F can be repre- quently is stored in a tape backup. sented in 4 bits, and 2 hex digits (1 digit for See also archive; high-capacity storage each set of 4 bits) can be stored in a single system; jukebox. byte. This means that 1 byte can contain any one of 256 different hex numbers, from High-Bit-Rate Digital Subscriber Line 0 through FF. Abbreviated HDSL. A high-speed data See also binary; decimal. transmission technology originally devel- oped by Bellcore that delivers high band- HFS See Hierarchical File System. width over existing twisted-pair copper hidden file In many operating systems, telephone lines. any file that has the hidden attribute set, HDSL is the most common Digital Sub- which indicates to the operating system that scriber Line (DSL) service and provides T1 information about the file should not ap- data rates of 1.544Mbps over lines of up to pear in normal directory listings. There may 3.6 kilometers, or 12,000 feet, in length. also be further restrictions on a hidden file, HDSL is symmetric, providing the same and users may not be able to delete, copy, or data rate in each direction. display the contents of such a file. The service is not intended for residential hidden share In Microsoft Windows purposes, but is used in the telephone com- 2000, a share whose name contains a dollar pany’s own private data networks, Internet sign as the last character. The names of hid- servers, and interexchange connections. den shares are not displayed under normal See also Asymmetric Digital Subscriber circumstances, although they are always Line; Digital Subscriber Line; Rate- visible in Computer Management. Adaptive Digital Subscriber Line; Single- See also common share; default shares; Line Digital Subscriber Line; Very-High- share; sharing. Bit-Rate Digital Subscriber Line. 167 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 168 Thursday, May 4, 2000 11:59 AM high-capacity storage system high-capacity storage system Abbre- them to concentrate on the logic of the viated HCSS. A data-storage system that problem at hand. extends the storage capacity of a Novell See also low-level language. NetWare server by integrating an optical- disk library, or jukebox, into the NetWare high memory area Abbreviated HMA. file system. In a computer running MS-DOS, the first Network users and applications can access 64KB of extended memory above the 1MB files and directories on the jukebox with the limit of 8086 and 8088 addresses. same NetWare commands and function Programs that conform to the Extended calls used to access files from a hard disk. Memory Specification (EMS) can use this The most frequently used HCSS files may memory as an extension of conventional be cached temporarily on the server hard memory. However, only one program can disk to speed up access times. HCSS can use or control HMA at a time. If MS-DOS also access a magnetic tape system. is loaded into the HMA, approximately 50KB more conventional memory becomes See also archive. available for use by applications. high-end An expensive, full-featured prod- See also expanded memory; extended uct from the top of a company’s product list. memory; memory management. See also low-end. High-Performance File System Ab- breviated HPFS. A file system available in High-level Data Link Control Abbrevi- OS/2 and Microsoft Windows NT that sup- ated HDLC. An international protocol de- ports the following: fined by the ISO (International Organization for Standardization), included in CCITT I Long, mixed-case filenames of up to 255 characters X.25 packet-switching networks. HDLC is a bit-oriented, synchronous protocol that pro- I As much as 64KB of extended attributes vides error correction at the data-link layer. per file In HDLC, messages are transmitted in vari- I Faster disk access with an advanced disk able-length units known as frames. cache for caching files and directory See also Synchronous Data Link Control. information I Highly contiguous file allocation that high-level language Any machine- eliminates file fragmentation independent programming language that uses English-like syntax in which each I Hard disks of up to 64GB in size statement corresponds to many assembly MS-DOS does not recognize the HPFS file language instructions. High-level languages structure, it cannot be used on a floppy disk, free programmers from dealing with the un- and it is not supported in Windows NT 4 or derlying machine architecture and allow later. 168 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 169 Thursday, May 4, 2000 11:59 AM hive HIGH-LEVEL DATA LINK CONTROL FRAME High-Performance Parallel Interface High Speed Serial Interface Abbrevi- Abbreviated HPPI. A parallel interface ated HSSI. A serial data communications standard from the American National Stan- interface optimized for speeds of up to dards Institute (ANSI) known as X3T9.3, 52Mbps. Often used for connecting an originally developed as an interface be- Asynchronous Transfer Mode (ATM) tween supercomputers and fast peripherals switch to a T3 Data Service Unit. such as disk arrays and frame buffers. See also Asynchronous Transfer Mode; Recently, HPPI has been extended for use in Data Service Unit; T3. networked computers and high-end work- stations. It provides a data rate of 800Mbps hijacking An attack on a computer sys- over 32-pair twisted-pair copper wire, tem in which an established TCP/IP session known as single HPPI, and 1,600Mbps over is redirected in mid-session to an unautho- 64 pairs, known as double HPPI. Connec- rized host system. tion length is limited to 25 meters (82 feet). See also spoofing. High-Performance Routing Abbreviat- hit On the World Wide Web, a request ed HPR. An internetworking protocol from from a browser for a file on the server. A hit IBM, intended as an upgrade to its Ad- on a Web page occurs whenever any file is vanced Peer-to-Peer Networking (APPN) accessed, whether it is a text document, a package. HPR provides internetworking graphic, a script, or an audio or video clip. capabilities similar to those of TCP/IP. If you access three files on a Web page, you See also Advanced Peer-to-Peer Network- generate three hits, so a hit is a poor mea- ing; Data Link Switching. sure of the number of people visiting a Web site, as it simply reflects the number of file High Sierra specification A specifica- requests made. tion for CD-ROM data that served as the basis for the ISO (International Organiza- hive A major logical division within the tion for Standardization) 9660 standard. It Microsoft Windows Registry. The Registry is called High Sierra because it was defined is divided into several hives: at a meeting held near Lake Tahoe in No- I HKEY_CLASSES_ROOT contains infor- vember 1985. mation about file associations. 169 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 170 Thursday, May 4, 2000 11:59 AM HMA I HKEY_CURENT_USER contains infor- home page On the World Wide Web, an mation about the currently logged on initial starting page. A home page may be user. prepared by an individual or by a corpora- I HKEY_LOCAL_MACHINE contains in- tion and is a convenient jumping-off point formation about the computer running to other Web pages or Internet resources. Windows, including details of applica- See also portal. tions, device drivers, and hardware. homogeneous network A network I HKEY_USERS contains information that consists of one type of workstation, about each active user with a user profile. server, network interface card, and operat- I HKEY_CURRENT_CONFIG contains ing system, with a limited number of appli- details about the current system cations, all purchased from a single vendor. configuration. All nodes use the same protocol and the I HKEY_DYN_DATA contains informa- same control procedures. tion about plug-and-play devices on the See also enterprise network; heteroge- system. neous network. You can view and edit the Registry using hooked vector An intercepted interrupt the regedit.exe program. vector that now points to a replacement in- See also key; sub-key. terrupt service routine (ISR) rather than to the original service routine. HMA See high memory area. hop A single link between two computer holy wars A fundamentally unresolv- systems that an e-mail message must cross able computer-related argument, in which on its way to its destination. A message may the participants spend most of their time have to pass over many hops to reach its ul- trying to establish often wildly personal timate destination; if it must pass between choices as carefully thought out and deeply five computers, it is said to have taken four considered technical evaluations. Topics hops to reach its destination. might include any version of Unix versus See also hop count. any other version of Unix, the C program- ming language versus C++ (or any other hop count In routing, the number of programming language), big endian sys- links that must be crossed to get from any tems versus little endian systems, and so on. given source node to any given destination node. Hop count is often used as a metric home directory In Unix, a directory that for evaluating a route for a least-cost rout- contains the files for a specific user. The ing algorithm. name of your home directory is kept in the password file, and when you log in, your horizontal application Any application current directory is always set to be your software that is broad in scope and not de- home directory. signed for use in one specific industry or 170 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 171 Thursday, May 4, 2000 11:59 AM HSSI setting. Word-processing software falls HotJava A highly interactive Web into this category, but software specifical- browser from Sun Microsystems that is ly designed to manage a medical practice written in the Java programming language. does not. HP See Hewlett-Packard Company. See also vertical application. HPFS See High-Performance File System. host The central or controlling computer in a networked or distributed processing HP OpenView Certified Consultant A environment which provides services that certification from Hewlett-Packard that other computers or terminals can access via recognizes technical competency to both the network. sell and support HP OvenView, a network management system used to monitor and host bus adapter Abbreviated HBA. A manage networks consisting of equipment board acting as an interface between the and software from multiple vendors. processor and the hard-disk controller in a Three specializations are available: network server, used by Novell NetWare to I Unix relieve the main processor of data-storage I Windows NT and retrieval tasks. Also known as a disk coprocessor board (DCB). I Unix and Windows NT combined The HBA and its disk subsystems make up HPR See High-Performance Routing. a disk channel. NetWare can access five HP-UX A version of Unix that runs on disk channels, with four controllers on each Hewlett-Packard computers. HP-UX in- channel, and eight hard-disk drives at- cludes BSD extensions, including the net- tached to each controller. work commands, the Korn shell, and a version of emacs. Visual User Environment Hot Fix A Novell NetWare feature that (VUE) is HP’s graphical user interface, with marks defective disk blocks dynamically so workspaces for different tasks, drag-and- that the operating system will not use them. drop functions, a text editor, a color icon editor, and other productivity tools. Data is redirected from any faulty blocks to a small portion of disk space set aside as the HP-UX also includes System Administra- Hot Fix redirection area. Hot Fix then tion Manager (SAM) for common adminis- marks the defective area as bad, and the trative tasks, such as adding new users, installing and configuring peripherals, server will not attempt to store data there managing processes, and scheduling jobs. again. By default, 2 percent of a disk parti- tion is set aside as the Hot Fix redirection HSM See Hierarchical Storage area. Management. See also fault tolerance. HSSI See High Speed Serial Interface. 171 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 172 Thursday, May 4, 2000 11:59 AM HTML HTML See HyperText Markup See also homogeneous network; hetero- Language. geneous network. HTTP See Hypertext Transfer Protocol. hybrid organization In Novell Directo- hub A device used to extend a network so ry Services (NDS), an organizational strat- that additional workstations can be at- egy that combines two or more of the tached. There are two main types of hubs: methods—locational, divisional, and workgroup. A hybrid organization makes I Active hubs amplify transmission signals most sense in a large organization. to extend cable length and ports. hypermedia A term used to describe I Passive hubs split the transmission signal, nonsequential applications that have inter- allowing additional workstations to be active, hypertext links between different added, usually at a loss of distance. multimedia elements— graphics, sound, In some star networks, a hub is the central text, animation, and video. controlling device. If an application relies heavily on text- Huffman coding In data compression, a based information, it is known as method of encoding data on the basis of the hypertext; however, if full-motion video, relative frequency of the individual elements. animation, graphics, and sound are used, Huffman coding is often used with text files; the application is considered hypermedia. the coding is based on how frequently each letter occurs, because it is a lossless compres- hypertext A method of presenting infor- sion method. Huffman coding is used in fax mation so that it can be viewed by the user transmissions. in a nonsequential way, regardless of how the topics were originally organized. See also data compression; lossless com- pression; lossy compression. Hypertext was designed to make a comput- er respond to the nonlinear way that hu- Hurd A project from the Free Software mans think and access information—by Foundation (FSF) to develop and distribute association, rather than according to the a free version of the Unix operating system linear organization of film, books, and for many different hardware platforms. speech. Hurd (or sometimes HURD) is considered a In a hypertext application, you can browse collection of all the GNU software, compil- through the information with considerable ers, editors, and utilities, as well as the op- flexibility, choosing to follow a new path erating system. each time you access the information. When See also Free Software Foundation; GNU. you click a highlighted word, you activate a link to another hypertext document, which hybrid network A network that uses a may be on the same Internet host or on a collection of different technologies, such as completely different system thousands of frame relay, leased lines, and X.25. miles away. These links depend on the care 172 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 173 Thursday, May 4, 2000 11:59 AM Hz that the document originator used when as- (W3C), at least in theory; the manufactur- sembling the document; unfortunately, ers of the most popular browsers have driv- many links turn into dead-ends. en this process in the past by creating their See also link rot. own non-standard HTML elements. HTML has been vital in the development of HyperText Markup Language Abbre- the World Wide Web; however, the func- viated HTML. A standard document for- tions that it performs via the Web browser matting language used to create Web pages and other hypertext documents. HTML is a are becoming restrictive. In part, this has subset of Standardized General Markup led to the development of other technolo- Language (SGML). gies, such as Java, Virtual Reality Modeling Language (VRML), and Extensible Mark- HTML defines the appearance and place- up Language (XML). ment on the page of elements such as fonts, graphics, text, links to other Web sites, and See also Extensible Markup Language; so on; it has nothing to do with the actual Java; Secure HTTP; Virtual Reality material presented. Hypertext documents Modeling Language. often have the filename extension .htm or .html. Hypertext Transfer Protocol Abbrevi- The published HTML standards have been ated HTTP. The command and control pro- revised several times. HTML version 2 was tocol used to manage communications the first version widely used on the World between a Web browser and a Web server. Wide Web and supported by the popular When you access a Web page, you see a Web browsers of the day. Subsequent revi- mixture of text, graphics, and links to other sions to the standard have added new documents or other Internet resources. HTML elements such as tables, text flow HTTP is the mechanism that opens the re- around images, frames, applets, and style lated document when you select a link, no sheets. matter where that document is located. Future HTML revisions will be developed by the World Wide Web Consortium Hz See hertz. 173 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 174 Thursday, May 4, 2000 11:59 AM I2O I I2O See Intelligent Input/Output. IBM Certified Specialist One of the many certifications from IBM, available in IAB See Internet Architecture Board. a range of specializations, including: IAC See Inter-Application I AIX System Administration Communication. I AIX Support IANA See Internet Assigned Numbers I AS/400 Associate System Operator Authority. I AS/400 Professional System Operator IBM See International Business Ma- I AS/400 Associate System Administrator chines Corporation. I AS/400 Professional System Administrator I OS/2 Warp Server Administration IBM 3270 A general name for a family of IBM system components—printers, termi- I LAN Server 4 Administration nals, and terminal cluster controllers—that IBM Certified Systems Expert One of can be used with a mainframe computer by the many certifications from IBM, available an SNA (Systems Network Architecture) in a range of specializations, including link. OS/2 Warp and OS/2 Warp 4. Software that emulates a 3270 terminal is IBM RS/6000 A set of seven or nine sep- available for all major operating systems. arate 32-bit chips used in IBM’s line of re- IBM cabling systems See Type 1-9 duced instruction set computing (RISC) cable. workstations. With as many as 7.4 million transistors, the IBM Certified Advanced Technical RS/6000 uses a superscalar design with four Expert One of the many certifications separate 16KB data-cache units and an 8KB from IBM, available in many specializa- instruction cache. The joint venture an- tions, including RS/6000 AIX. nounced between IBM, Apple, and Motor- IBM Certified AIX User One of the ola in late 1991 specified the development many certifications from IBM. This one is of a single-chip version of the RS/6000 ar- available to the AIX user. chitecture called the PowerPC. IBM Certified Expert One of the many IBM Suite for Windows NT A software certifications from IBM, available in a suite from IBM for Microsoft Windows NT range of specializations, including OS/2 that includes five major modules: Warp Server and OS/2 LAN Server. I Intel’s LANDesk Manager 174 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 175 Thursday, May 4, 2000 11:59 AM IEEE standards I Lotus Domino selected by moving a mouse or another I IBM’s DB2 Universal Database (UDB) pointing device. I IBM’s eNetwork Communications Server An icon can represent an application, a document, embedded and linked objects, a I IBM’s ADSTAR Distributed Storage hard disk drive, or several programs col- Manager (ADSM) lected in a group. The suite is available in both department and enterprise versions. IDE See Integrated Drive Electronics. IBM ThinkPad A series of innovative and identity In Microsoft Outlook Express, a popular notebook computers from IBM. feature that allows you to create multiple accounts so that you can keep business and The ThinkPad first introduced the touch- personal e-mail associated with different sensitive dual-button pointing stick (called identities. a TrackPoint), the pencil-eraser–like de- vice, found between the G, H, and B keys. idle cell In Asynchronous Transfer It is now included on many portable com- Mode, a cell transmitted purely to keep net- puters and replaces the mouse. work traffic at a specific level. The top-of-the-line ThinkPad 770 runs a See also Asynchronous Transfer Mode. 300MHz Pentium II processor, an 8.1GB hard disk, a 56K modem, a 14.1-inch IDS See Intrusion Detection System. SVGA screen with resolutions up to 1280 × IDT See Integrated Device Technology, 1024, and as much as 320MB of memory. Inc. IC See integrated circuit. IE See Internet Explorer. ICA See Independent Computing IEC See Interexchange Carrier. Architecture. IEEE See Institute of Electrical and Elec- ICMP See Internet Control Message tronics Engineers. Protocol. IEEE standards The Institute of Electri- ICP See Internet Content Provider. cal and Electronics Engineers (IEEE), acting Icon A general-purpose high-level pro- as a coordinating body, has established a gramming language with a large number of number of telecommunications standards, string-processing functions, developed by including Group 802 as follows: Ralph Griswold at the University of Arizo- I 802.1D An access-control standard for na. Icon has a C-like syntax and is available bridges linking 802.3, 802.4, and 802.5 both as a compiler and as an interpreter. networks. icon In a graphical user interface, a small I 802.2 A standard that specifies the Data screen image representing a specific element Link layer for use with 802.3, 802.4, and that the user can manipulate in some way, 802.5 networks. 175 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 176 Thursday, May 4, 2000 11:59 AM IETF I 802.3 1Base5 A standard matching the broadband techniques to other IEEE AT&T StarLAN product with a 1Mbps subcommittees. data transfer rate and a maximum cable- I 802.8 The Fiber-Optic Technical segment length of 500 meters (1640 feet). Advisory Committee provides advice on I 802.3 10Base2 An implementation of the fiber-optic technology to other IEEE Ethernet standard on thin Ethernet cable subcommittees. with a data transfer rate of 10Mbps, and a I 802.9 The Integrated Data and Voice maximum cable-segment length of 185 (IDV) Networks group is currently work- meters (600 feet). ing to integrate data, voice, and video to I 802.3 10Base-T A standard for Ether- 802 LANs and ISDN. Now more com- net over unshielded twisted-pair wiring, monly referred to as Iso-Ethernet. the same wiring and RJ45 connectors I 802.10 The Network Security Techni- used with telephone systems. The stan- cal Advisory Group is developing a stan- dard is based on a star topology, in which dard definition of a network security each node connects to a central wiring model. center, with a cable-length limitation of I 802.11 The Wireless Networking group 100 meters (325 feet). is developing standards for wireless I 802.3 10Broad36 A standard for long- networks. distance Ethernet with a 10Mbps data I 802.12 The Demand Priority group is rate and a maximum cable-segment working on standards for the 100Mbps length of 3600 meters (11,800 feet). Ethernet standard. I 802.4 A standard for bus topology net- I 802.14 The Cable Modems group is de- works that use token passing to control fining standards for data transport over access and network traffic, running at traditional cable TV networks. 10Mbps. Not widely implemented. You will also see many of these standards I 802.5 A standard for ring networks that referred to by their ISO reference numbers. use token passing to control access and IEEE standards 802.1 through 802.11 are network traffic, running at 4Mbps or also known as ISO standards 8802.1 16Mbps. It is used by IBM’s Token Ring through 8802.11. network. For more information, see the entries on the individual standards. I 802.6 An emerging standard for metro- politan area networks (MANs) transmit- IETF See Internet Engineering Task ting voice, video, and data over two Force. parallel fiber-optic cables, using signaling rates of up to 155Mbps. IFS See installable file system. I 802.7 The Broadband Technical Advi- IGMP See Internet Group Management sory Committee provides advice on Protocol. 176 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 177 Thursday, May 4, 2000 11:59 AM Incumbent Local Exchange Carrier IGP See Interior Gateway Protocol. (the ability to store energy in the form of a magnetic field), and resistance (the ability IGRP See Interior Gateway Routing to impede or resist the flow of electric cur- Protocol. rent), measured in ohms. IIOP See Internet Inter-ORB Protocol. Impedance can be described as the apparent IKE Abbreviation for Internet Key resistance to the flow of alternating current Exchange. at a given frequency. Mismatches in imped- ance along a cable cause distortions and re- See ISAKMP/Oakley. flections. Each transmission protocol and network topology specifies its own stan- ILEC See Incumbent Local Exchange dards for impedance. Carrier. IMA See Inverse Multiplexing over ATM. impersonation attack An attack in which a hostile computer system masquer- image map A graphical inline image on ades as a trusted computer. a Web page that contains more than one See also brute-force attack; dictionary link. Each region of the image map is linked attack; social engineering to a different Web resource; you can click a part of the image to retrieve the appropriate implied security equivalence In Nov- resource. ell Directory Services, when an object re- See also inline image. ceives the rights of the object’s parent, it is said to be security equivalent. Also known imaging The process of capturing, stor- as container security equivalence. The In- ing, cataloging, displaying, and printing herited Rights Filter does not affect this. graphical information, as well as scanning paper documents for archival storage. See also explicit security equivalence; In- herited Rights Filter; Novell Directory Ser- Network users can store and then retrieve vices; security equivalence. imaged documents from large, centralized image-storage systems, using applications I-Mux See inverse multiplexing. such as Lotus Notes or other groupware. See also document management; high- incremental backup A backup of a hard capacity storage system; optical character disk that consists of only those files created recognition. or modified since the last backup. See also differential backup; full backup. IMAP See Internet Mail Access Protocol. Incumbent Local Exchange Carrier impedance An electrical property of a Abbreviated ILEC. A term coined from the cable that combines capacitance (the ability Telecommunications Act of 1996 to describe to store an electrical charge), inductance the incumbent local telephone company, 177 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 178 Thursday, May 4, 2000 11:59 AM Independent Computing Architecture providing local transmission and switching viruses are triggered by particular dates, services. others by specific events on the system. See also Competitive Local Exchange See also antivirus program; boot sector vi- Carrier. rus; file-infecting virus; inoculate; macro virus; multipart virus; polymorphic virus; Independent Computing Architecture stealth virus; Trojan Horse; vaccine; virus. Abbreviated ICA. A presentation service protocol developed by Citrix that transports information node Abbreviated i-node, mouse clicks, keystrokes, and screen updates sometimes written inode, pronounced between a thin client and the server. ICA “eye-node.” In Unix, a data structure on works with Microsoft Windows, Macin- disk that describes a file. tosh, and Unix clients and runs on top of Each directory entry associates a filename TCP/IP, IPX/SPX, and NetBIOS. with an i-node; although a single file may See also thin client. have several filenames, one for each link , a file has only one i-node. Within a filesys- Independent Software Vendor Ab- tem, the number of i-nodes, and therefore breviated ISV. A company that develops the number of files, is defined when the sys- and sells computer software but is com- tem is first initialized. pletely independent of the makers of the An i-node contains all the information Unix hardware upon which the software runs. needs to be able to access the file, including Industry Standard Architecture Ab- the file’s length, the times that the file was breviated ISA. The 16-bit bus design first last accessed or modified, owner and group used in IBM’s PC/AT computer in 1984. ID information, access permissions, the ISA has a bus speed of 8MHz and a maxi- number of links to the file, and the disk ad- mum throughput of 8MBps. EISA (Extend- dress of the data blocks that contain the file ed Industry Standard Architecture) is a 32- itself. bit extension to this bus. See also i-node table. INETCFG A Novell NetWare 4 NLM information warehouse A central used to set up and configure AppleTalk, In- repository containing a company’s current ternet Protocol (IP) and Internetworking and historical data in a form that can be Packet eXchange (IPX) protocols on the accessed quickly and easily by users to aid server. in their business decision making. IBM has infection The presence of a virus or a a large number of products for building Trojan Horse within a computer system; fully automated enterprise-wide data the virus may be active in memory or warehouses. present on the hard disk. Informix-4GL Certified Professional The infection may remain hidden from the A professional certification from Informix user for a considerable length of time. Some Software aimed at developers proficient in 178 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 179 Thursday, May 4, 2000 11:59 AM initialize creating custom database applications us- of portable devices is implementing infrared ing Informix-4GL. communications at some level. See also Infrared Data Association; mobile Informix Software, Inc. A major sup- computing; wireless communications. plier of object-oriented and relational data- base products, based in Menlo Park, inherited rights Rights (in Novell Net- California. Ware) or permissions (in Microsoft Win- For more information on Informix Soft- dows 2000) received by an object from its ware, Inc., see www.informix.com. parent object. In Novell NetWare, inherited rights can be blocked by the Inherited Infrared Data Association Abbreviat- Rights Filter or by an explicit assignment. ed IrDA. A trade association of more than See also Inherited Rights Filter. 150 computer and telecommunications hardware and software suppliers, including Inherited Rights Filter Abbreviated Hewlett-Packard, Apple Computer, AST, IRF. In Novell Directory Services (NDS), Compaq, Dell, IBM, Intel, Motorola, Nov- the mechanism that controls the rights a ell, and others. trustee can inherit from parent directories IrDA is concerned with defining stan- or container objects. dards for products that use wireless Inheritance allows an assignment applied at communications. one point to apply to everything below that For more information on IrDA, see www point in the file and directory structure. The .irda.org. IRF for any file, directory, or object is a part of NetWare’s access control information. infrared transmission A method of In NetWare 3, the IRF was known as the In- wireless transmission that uses part of the herited Rights Mask and applied only to the infrared spectrum to transmit and receive file system. signals. See also Inherited Rights Mask; NETAD- Infrared transmissions take advantage of a MIN; trustee; trustee assignment. frequency range just below that of visible light, and they usually require a line-of- Inherited Rights Mask Abbreviated sight connection between transmitter and IRM. In NetWare 3, the mechanism that receiver. controls the rights a trustee can inherit. By Infrared transmission can be used to send default, IRM allows all rights to be inherit- documents from portable computers to ed. Both files and directories have individ- printers, to transmit data between portable ual IRM controls. computers, to exchange information be- See also Inherited Rights Filter; trustee; tween computers and cellular telephones trustee assignment. and faxes, and to connect to home entertain- ment systems. Almost every manufacturer initialize 1. To start up a computer. 179 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 180 Thursday, May 4, 2000 11:59 AM inline image 2. In the Macintosh, the process of prepar- changed its name in 1988. Well known for ing a new, blank floppy or hard disk for use. its dBASE database products, the company Initializing completely obliterates any in- also markets Delphi Client/Server Suite, a formation previously stored on the disk. visual rapid applications development envi- 3. To assign a beginning value to a variable. ronment, and JBuilder, a set of Java pro- gramming language development tools. See also formatting. For more information on Inprise Corpora- inline image On a Web page, an image tion, see www.inprise.com. displayed along with accompanying text. The process of placing the image on the input/output Abbreviated I/O. The page is known as inlining. transfer of data between the computer and its peripheral devices, disk drives, termi- inoculate To protect a file against attack nals, and printers. from a virus by recording characteristic in- formation about it and then monitoring any input/output bound Abbreviated I/O changes. bound. A condition in which the speed of operation of the input/output port limits See also antivirus program; boot sector vi- the speed of program execution. Getting the rus; file-infecting virus; infection; macro vi- data into and out of the computer is more rus; multipart virus; polymorphic virus; time-consuming than actually processing stealth virus; Trojan Horse; vaccine; virus. that same data. i-node See information node. See also computation bound. i-node table In Unix, a list of all the INSTALL A Novell NetWare server con- i-nodes in a filesystem. Within the i-node sole NetWare Loadable Module (NLM) table, each i-node is known by a number— used for managing, maintaining, and up- the i-number, or index number. If a file is dating NetWare servers. INSTALL can be defined by i-node #300, it is said to have an used for the following tasks: i-number of 300. See also information node. I Creating, deleting, and managing hard- disk partitions and NetWare volumes on in-place migration In Novell NetWare, the server a method of upgrading an existing Net- I Installing NetWare and other additional Ware server to NetWare 4, which includes products and updating the license or reg- converting the file system and updating the istration disk network operating system. I Adding, removing, checking, and unmir- See also across-the-wire migration. roring hard disks Inprise Corporation Originally known I Changing server startup and configura- as Borland International, the company tion files 180 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 181 Thursday, May 4, 2000 11:59 AM Integrated Device Technology, Inc. install To configure and prepare hard- Institute of Electrical and Electronics ware or software for operation. Engineers Abbreviated IEEE, pro- nounced “eye-triple-ee.” A membership or- Many application packages have their own ganization, founded in 1963, including installation programs, which copy all the engineers, students, and scientists. IEEE required files from the original distribution also acts as a coordinating body for com- disks into appropriate directories on your puting and communications standards. hard disk and then help to configure the program to your own operating require- For more information in IEEE, see www.ieee.org. ments. Microsoft Windows programs are installed by a program called Setup. See also IEEE standards. installable file system Abbreviated instruction set The set of machine-lan- IFS. A file system that is loaded dynamically guage instructions that a processor recog- by the operating system when it is needed. nizes and can execute. Different file systems can be installed to An instruction set for reduced instruction support specific needs, in just the same way set computing (RISC) may only contain a as device drivers are loaded to support spe- few instructions; a computer that uses cific hardware. complex instruction set computing (CISC) may be able to recognize several hundred installation program A program whose instructions. sole function is to install (and sometimes configure) another program. INT 14 See Interrupt 14. The program guides the user through what integrated circuit Abbreviated IC, also might otherwise be a rather complex set of known as a chip. A small semiconductor choices, copying the correct files into the circuit that contains many electronic right directories, decompressing them if components. necessary, and asking for the next disk Integrated Device Technology, Inc. when appropriate. An installation program may also ask for a person’s name and a Abbreviated IDT. An established manufac- turer of SRAM, specialty memory, and em- company name so that the startup screen bedded microprocessors, who has recently can be customized. Microsoft Windows moved into producing clones of Intel micro- programs are installed by a program called processors. IDT’s first WinChip, originally Setup. known as the C6, shipped in limited quan- Installer service In Microsoft Windows tities in 1997 and 1998, and the company 2000, a service that manages all aspects of recently announced the WinChip 2 and application installation, removal, and the WinChip 2+. separate configuration of components of For more information on Integrated Device large packages such as Office 2000. Technology, see www.idt.com. 181 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 182 Thursday, May 4, 2000 11:59 AM Integrated Drive Electronics Integrated Drive Electronics Abbrevi- this problem, ISA suggests that routers be ated IDE. A popular hard-disk interface able to reserve resources for specific data standard, used for disks in the range of streams called flows. A flow might be video 40MB to 1.2GB, requiring medium to fast data from a source to a destination or from data-transfer rates. The electronic control a source to multiple destinations. circuitry is located on the drive itself, thus See also IP over ATM; IP switching; quality eliminating the need for a separate hard- of service. disk controller card. See also Enhanced Small Device Interface; Integrated Services Digital Network Small Computer System Interface; ST506 Abbreviated ISDN. A standard for a world- Interface. wide digital communications network orig- inally designed to replace all current systems Integrated On-Demand Network with a completely digital, synchronous, full- Abbreviated ION. A new high-capacity duplex transmission system. residential and business service from Computers and other devices connect to Sprint that allows customers to simulta- ISDN via simple, standardized interfaces. neously make a phone call, send/receive a They can transmit voice, video, and data, fax, and access the Internet using a single all on the same line. connection. See also Basic Rate ISDN; Broadband Inte- The service is based on a mixture of broad- grated Services Digital Network; Primary band technology, such as Asynchronous Rate ISDN. Transfer Mode (ATM) and Digital Sub- scriber Line (DSL). Deployment of the net- integrated software Application soft- work is based on a partnership with three ware that combines the functions of several other companies—Cisco Systems, Bellcore, major applications, such as a spreadsheet, a and Radio Shack. database, a word processor, and a commu- See also Asynchronous Transfer Mode; nications program, into a single package. Digital Subscriber Line. Microsoft Works is an example of integrat- ed software. Integrated Services Architecture Ab- Integrated software provides a consistent breviated ISA. A proposed extension to the user interface in all the modules and allows Internet standards that would provide inte- the user to transfer data from one part of grated services in support of real-time ap- the system to another quickly and easily. It plications over the Internet. is also usually inexpensive. Unfortunately, integrated software packages do not typi- Using current standards, real-time applica- cally offer all the complex features available tions do not work well over the Internet with their stand-alone counterparts. because of variable and unpredictable queuing delays and other losses. To solve See also software suite. 182 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 183 Thursday, May 4, 2000 11:59 AM Intel Corporation INTEGRATED SERVICES DIGITAL NETWORK Integrated-Private Network-to- Intel has developed a wide range of pro- Network Interface Abbreviated I-PNNI. cessors and board-level products that are A routing protocol based on the Asynchro- used in applications as varied as personal nous Transfer Mode (ATM) Forum’s Private computers, automobiles, robots, and Network-to-Network Interface (PNNI) supercomputers, as well as the multibus standard that allows ATM switches to architecture that is used in many industri- communicate. al and proprietary applications. Intel also See also Private Network-to-Network manufactures modems, fax modems, Interface. memory chips, flash memory products, and other peripheral devices. The name Intel Corporation The world’s largest Intel is a contraction of Integrated manufacturer of microprocessors, supplying Electronics. the processors used in more than 80 percent of the world’s personal computers. 183 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 184 Thursday, May 4, 2000 11:59 AM Intelligent Input/Output For more information on Intel Corpora- See also Solaris. tion, see www.intel.com. Inter-Application Communication Intelligent Input/Output Abbreviated Abbreviated IAC. In the Macintosh operat- I2O; pronounced “eye-two-oh.” A specifi- ing system, a feature of the System software cation from Intel Corporation that divides that allows independent applications to the traditional device driver into two parts; share and exchange information. IAC takes I The part concerned with managing the two main forms: device I Publish-and-subscribe, which allows us- I The part concerned with interfacing to the ers to create documents made of compo- operating system nents created by multiple applications. By making this distinction, that part of the I Apple events, which let one application driver concerned with managing the device control another. For example, two pro- now becomes portable across operating grams can share common data, and one systems. program can request that the other per- I2O is also designed to work with intelligent form some action. input/output subsystems, with support for IAC is often referred to as program linking message passing between multiple indepen- in the System manuals. dent processors, so that the host system can be relieved of all the interrupt-intensive tasks Interexchange Carrier Abbreviated associated with servicing device drivers. IXC; sometimes abbreviated IEC. A term coined from the Telecommunications Act Several operating system vendors, includ- of 1996 to describe voice and data long- ing SCO, Microsoft, and Novell, have an- distance telephone companies, including nounced support for I2O in future AT&T, MCI, Sprint, and Worldcom. products. See also Competitive Local Exchange Car- intelligent hub See smart hub. rier; Incumbent Local Exchange Carrier; Local Exchange Carrier. intelligent terminal A terminal connect- ed to a large computer, often a mainframe, interface The point at which a connection that has some level of local computing power is made between two hardware devices, be- and can perform certain operations indepen- tween a user and a program or operating sys- dently from the remote computer, but does tem, or between two applications. not usually have any local disk-storage capacity. In hardware, an interface describes the logical and physical connections, as in See also dumb terminal. RS-232-C, and is often considered synon- Interactive Unix A version of Unix from ymous with the term port. Sun Microsystems based on AT&T’s Sys- A user interface consists of the means by tem V Release 3.2 kernel. which a program communicates with the us- 184 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 185 Thursday, May 4, 2000 11:59 AM International Business Machines Corporation er, including a command line, menus, dialog DRAM requires that its contents be updat- boxes, online help systems, and so on. User ed at least every thousandth of a second, interfaces can be classified as character- and while this update is taking place, it can- based, menu-driven, or graphical. not be read by the processor. Interleaved Software interfaces are application pro- memory divides available memory into gramming interfaces (APIs) and consist of banks so that the processor can read from the codes and messages used by programs one bank while the other is cycling and so to communicate behind the scenes. does not have to wait. Because interleaved memory does not require special hardware, See also graphical user interface. it is one of the most cost-effective ways of interface standard Any standard way speeding up system operation. of connecting two devices or elements that See also wait state. have different functions. internal command Any operating sys- Personal computers use many different in- tem command that is not a separate pro- terface standards. These include Small gram and is always available to the user. In Computer System Interface (SCSI), Inte- MS-DOS, DIR, COPY, and TYPE are ex- grated Drive Electronics (IDE), and the En- amples of internal commands. hanced Small Device Interface (ESDI) for hard disks; RS-232-C and the Centronics See also external command. parallel interface for serial devices and par- internal modem A modem that plugs allel printers; and the OSI Reference Model into the expansion bus of a personal com- for LAN communications over a network. puter or into the PCMCIA connector of a Interior Gateway Protocol Abbreviat- laptop computer. ed IGP. The protocol used on the Internet See also external modem. to exchange routing information between routers within the same domain. internal security Security measures tak- See also Border Gateway Protocol; Exter- en to prevent unauthorized computer ac- nal Gateway Protocol. cess from within an organization. See also Intrusion Detection System. Interior Gateway Routing Protocol Abbreviated IGRP. A distance-vector rout- International Business Machines ing protocol from Cisco Systems for use in Corporation Abbreviated IBM, also large heterogeneous networks. known as “Big Blue.” Known originally for See also heterogeneous network. its huge range of mainframe computers, IBM introduced the IBM PC, which quickly interleaved memory A method of emerged as an industry standard. Since its speeding up access by dividing dynamic introduction in 1981, the PC has seen many RAM (DRAM) into two (or more) separate changes, and an enormous number of com- banks. panies worldwide now manufacture or 185 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 186 Thursday, May 4, 2000 11:59 AM International Organization for Standardization market hardware, software, and peripheral See also OSI Reference Model. devices for IBM-compatible computers. International Telecommunication IBM also has a huge research effort, owns Union Abbreviated ITU. The U.N. um- thousands of patents, and has introduced brella organization that develops and stan- many innovative products, including the dardizes telecommunications worldwide. small, touch-sensitive TrackPoint, which replaces the mouse on many portable com- The ITU also contains the CCITT, the In- puters, a 1000MHz chip, and a 3.5-inch ternational Frequency Registration Board hard disk drive capable of storing up to (IFRB), and the Consultative Committee 17GB of information. on International Radio (CCIR). In popular For more information on IBM, see usage, CCITT standards are being referred www.ibm.com. to as ITU standards. See also Advanced Program-to-Program For more information on ITU, see Communications; Advanced Peer-to- www.itu.ch. Peer Networking; Advanced Interactive Internet The world’s largest computer Executive; AS/400; Systems Network network, consisting of millions of comput- Architecture. ers supporting tens of millions of users in hundreds of countries. The Internet is International Organization for Stan- growing at such a phenomenal rate that any dardization Sometimes mistakenly re- size estimates are quickly out of date. ferred to as the International Standards Organization, and commonly referred to as The Internet was originally established to ISO, which is not an abbreviation but a der- meet the research needs of the U.S. defense ivation of the Greek word isos, which industry, but it has grown into a huge glo- means equal and which is a term that was bal network serving universities, academic adopted by the International Organization researchers, commercial interests, govern- for Standardization. An international stan- ment agencies, and private individuals, dards-making body, based in Geneva, with both in the United States and overseas. representatives from more than 100 coun- The Internet uses TCP/IP protocols, and In- tries. The ISO establishes global standards ternet computers run many different oper- for communications and information ex- ating systems, including VMS, Microsoft change. ANSI is the U.S. member of the Windows 2000, and many variations of ISO. Unix. The seven-layer OSI Reference Model for No government agency, single person, or computer-to-computer communications is corporate entity controls the Internet; there one of the ISO’s most widely accepted rec- is no Internet Corporation working behind ommendations in the area of networking. the scenes. All decisions on methods and For more information on ISO, see standards are made by committees based on www.iso.ch. input from users. 186 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 187 Thursday, May 4, 2000 11:59 AM Internet abbreviations Internet use falls into several major areas, seen their function absorbed into the pop- including: ular Web browsers. I E-mail Electronic mail. Well over 80 The sheer volume of information available percent of the people who use the Internet through the Internet is staggering; however, regularly use it for e-mail. You can send because the Internet is a casual grouping of e-mail to recipients in more than 150 many networks, there is often no easy way countries, as well as to subscribers of com- to determine the location of specific infor- mercial online services, such as America mation. This has led to the emergence of Online, CompuServe, Delphi, Genie, and several prominent portal sites and a number Prodigy. of popular search engines. Internet access can be via a permanent net- I IRC chat A service that connects large work connection or by dial-up through one numbers of users in real-time group of the many Internet Service Providers (ISP). discussions. See also Internet address; Internet Archi- I Mailing lists Private discussion groups tecture Board; Internet Assigned Numbers accessed by e-mail. Authority; Internet Engineering Task Force; Internet Research Task Force; Inter- I Usenet newsgroups Larger public dis- net Society; portal; Request for Comment; cussion groups that focus on a specific search engine; Usenet; World Wide Web; subject. Posts and threads in newsgroups World Wide Web Consortium. are accessed using a newsreader. I World Wide Web Hypertext-based sys- internet See internetwork. tem for finding and accessing Internet re- Internet abbreviations Like any cul- sources; the World Wide Web is one of the ture, the Internet world has developed a fastest growing and most exciting of all whole language of abbreviations, acro- Internet applications. nyms, and slang expressions. The following Other Internet applications such as Go- list describes some of the common terms pher, FTP and anonymous ftp, and Telnet you are likely to encounter in Usenet news- have either been overshadowed by the groups or in your e-mail. growth of the World Wide Web or have See also emoticon; smiley. Abbreviation Description aTdHvAaNnKcSe Thanks in advance AWTTW A word to the wise BRB Be right back 187 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 188 Thursday, May 4, 2000 11:59 AM Internet abbreviations Abbreviation Description BTW By the way CU See you FAQ Frequently asked question FAQL Frequently asked question list FOAF Friend of a friend F2F Face to face FWIW For what it’s worth GR&D Grinning, running, and ducking IMHO In my (sometimes not very) humble opinion IWBNI It would be nice if IYFEG Insert your favorite ethnic group LOL Laughing out loud MEGO My eyes glaze over MOTAS Member of the appropriate sex MOTOS Member of the opposite sex MOSS Member of the same sex Ob- Obligatory, as in ob-joke OTOH On the other hand PD Public domain 188 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 189 Thursday, May 4, 2000 11:59 AM Internet Architecture Board Abbreviation Description PITA Pain in the ass PMFJI Pardon me for jumping in RL Real life ROTFL Rolling on the floor laughing RTFM Read the (expletive deleted) manual SO Significant other TIA Thanks in advance TTFN Ta ta for now WRT With respect to YMMV Your mileage may vary $0.02 My two cents worth Internet address A location on the In- net for Internet administrative ternet. An Internet address takes the form organizations someone@abc.def.xyz, in which someone is See also bang path; IP address. a user’s name or part of a user’s name, @abc is the network computer of the user, and Internet Architecture Board Abbrevi- def is the name of the host organization. The last three letters denote the kind of in- ated IAB. A technical advisory group of the stitution the user belongs to: Internet Society (ISOC). The IAB manages the editing and publication of Request for edu for educational Comments (RFCs), serves as an appeals com for commercial board, and provides other services to the gov for government ISOC. mil for the military For more information on the IAB, see org for non-profit organizations www.iab.org/iab. 189 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 190 Thursday, May 4, 2000 11:59 AM Internet Assigned Numbers Authority Internet Assigned Numbers message in an IP datagram and then sending Authority Abbreviated IANA. A central the datagram back to the original source. clearinghouse for the assignment and coor- ICMP is also used by the Ping command. dination of Internet protocol parameters, See also Ping. such as Internet addresses, protocol vari- ables and numbers, and domain names. Internet Engineering Task Force Ab- For more information on the IANA, see breviated IETF. Provides technical and de- www.isi.edu/iana. velopment services for the Internet and Internet Connection Sharing In Mi- creates, tests, and implements Internet stan- crosoft Windows 98 and Windows 2000, a dards that are then approved and published mechanism that allows networked com- by the Internet Society (ISOC). The techni- puters to share a single connection to the cal work is done within the IETF working Internet. groups. Internet Connection Sharing works with For more information on IETF, see any kind of Internet connection, including www.ietf.org. modems, Integrated Services Digital Net- work (ISDN), cable modem, or Digital Sub- Internet Explorer Abbreviated IE. In scriber Line (DSL). Microsoft Windows, a Web browser used to display Internet resources. Internet Content Provider Abbreviat- ed ICP. A company that will design and de- See also security zone. liver content for your Web site. See also Internet Service Provider. Internet file types The Internet offers many opportunities for downloading files Internet Control Message Protocol from a huge number of Internet hosts. Abbreviated ICMP. An error-reporting pro- These files may have been generated on dif- tocol that works with Internet Protocol (IP) ferent computer systems, so before you and provides the functions used for network- spend time downloading a file, it is impor- layer management and control. tant to understand the type of file you are Routers send ICMP messages to respond to dealing with. Table I.1 lists many of the undeliverable datagrams by placing an ICMP common file types you may encounter. TABLE I.1 INTERNET FILE TYPES Filename Extension Description tar A tape archive created by the tar utility. Z A file created by the compress utility. You must use uncompress to restore the file before you can use it. 190 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 191 Thursday, May 4, 2000 11:59 AM Internet file types TABLE I.1 INTERNET FILE TYPES (CONTINUED) tar.z A compressed tape archive file. z A file created by the pack utility. You must use unpack to restore the file before you can use it. zip A file created by PKZIP or WinZip. You must unzip the file before you can use it. gz A file created by the GNU gzip utility. You must decompress the file before you can use it. hqx A compressed Macintosh file. sit A Macintosh file compressed by StuffIt. tif/tiff A graphics file in TIF format. gif A graphics file in GIF format. htm/html A Web page in HyperText Markup Language. jpg/jpeg A graphics file in JPEG format. mpg/mpeg A video file in MPEG format. txt A text file. 1 An nroff source file. ps A PostScript file ready for printing. uue A uuencoded file. You must use uudecode before you can use the file. uue.z A compressed uuencoded file. shar A Usenet newsgroup archive file created by the shar utility. shar.z A compressed shar file. 191 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 192 Thursday, May 4, 2000 11:59 AM Internet Group Management Protocol Internet Group Management Pro- IMAP allows users to download mail selec- tocol Abbreviated IGMP. An Internet tively, to look at a message header, to protocol used in multicasting. download only part of a message, to store messages on the server in a hierarchical IGMP allows hosts to add or remove structure, and to link to documents and themselves from a multicast group. A mul- Usenet newsgroups. IMAP also has strong ticast group is a collection of computers re- authentication features and supports Ker- ceiving packets from a host that is trans- beros. Search commands are also available mitting multicast packets with IP Class D so that users can locate messages based on addresses. Group members can join the their subject or header or based on content . group and leave the group; when there are no more members, the group simply ceases See also Kerberos; Post Office Protocol; to exist. Simple Mail Transfer Protocol See also Class D network; IP Multicast; multicasting. Internet Network File System Abbre- viated Internet NFS. A TCP/IP-based pro- Internet Inter-ORB Protocol Abbrevi- tocol from Sun Microsystems used for ated IIOP. That part of the Common Object sharing and accessing files remotely over Request Broker Architecture (CORBA) the Internet. that allows CORBA-based interaction over See also Network File System. TCP/IP networks (including the Internet) by replacing Hypertext Transfer Protocol Internet Network Information Center (HTTP). Abbreviated InterNIC. A cooperative ven- See also Common Object Request Broker ture between AT&T, the National Science Architecture. Foundation, and Network Solutions, Inc., that provides domain name registration and Internet Key Exchange See ISAKMP/ assigns IP addresses for use on the Internet. Oakley. For more information on InterNIC, see Internet Mail Access Protocol Abbre- www.internic.net. viated IMAP. A protocol that defines how users can access and store incoming e-mail Internet NFS See Internet Network File messages. System. Internet mail servers use Simple Mail Internet Protocol Abbreviated IP, IP Transfer Protocol (SMTP) to move e-mail version 4, and IPv4. The session-layer pro- from one server to another and then use tocol that regulates packet forwarding by either IMAP or Post Office Protocol (POP) tracking addresses, routing outgoing mes- to manage the e-mail and store messages in sages, and recognizing incoming messages the appropriate mailboxes. in TCP/IP networks and the Internet. 192 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 193 Thursday, May 4, 2000 11:59 AM Internet Relay Chat The IP packet header contains the following A value of 6 indicates Transmission Con- fields: trol Protocol (TCP), and a value of 17 in- dicates User Datagram Protocol (UDP). I Version Version number of the protocol. I Header checksum Checksum for the I IHL (Internet header length) Length of header. the header information. The header length can vary; the default header is five 32-bit I Source address IP address of the sender. words, and a sixth word is optional. I Destination address IP address of the I TOS (Type of Service) Various levels or recipient. types of service. I Options/padding Optional information I Total length Length of the datagram in and padding. bytes, which can be a minimum of 576 See also IP multicast; IPv6; Transmission bytes to a maximum of 65,535 bytes. Control Protocol; Transmission Control I Identification Information that the re- Protocol/Internet Protocol. ceiving system can use to reassemble frag- mented datagrams. Internet Relay Chat Abbreviated IRC. An Internet client/server application that al- I Flags The first flag bit (DF) specifies that lows large groups of people to communi- the datagram should not be fragmented cate interactively; developed by Jarkko and must therefore travel over networks Oikarinen in Finland. that can handle the size without fragment- ing it. The second flag bit (MF) indicates Specific channels are devoted to a particular whether this is the last fragment. subject, from the sacred to the profane, and channels come and go regularly as interest I Fragment Offset An indication of where levels change. Each channel has its own this datagram belongs in the set of frag- name, usually prefaced by the pound sign ments; is used during reassembly. (#), as in #hottub. I Time-to-Live (TTL) Originally, the When you join a channel, you can see what time in seconds that the datagram could others have already typed; when you type a be in transit; if this time was exceeded, line and press Enter, everyone else sees your the datagram was considered lost. Now text. Most, but not all, of the conversations interpreted as a hop count and usually set are in English. If someone asks you for a to the default value 32 (for 32 hops), this password during an IRC session, don’t be value is decremented by each router tempted to give it; someone is trying to trick through which the packet passes. Once it you into divulging important information reaches zero, the datagram is discarded. about your system. I Protocol Identifies the transport-layer See also listserver; mailing list; news- process intended to receive the datagram. group; Usenet. 193 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 194 Thursday, May 4, 2000 11:59 AM Internet Research Task Force INTERNET PROTOCOL FIELDS Internet Research Task Force Abbre- net, Internet applications, and internet- viated IRTF. An Internet organization that working technologies. creates long- and short-term research ISOC also coordinates the activities of groups concentrating on protocols, archi- many other Internet groups, including the tecture, and technology issues. Internet Architecture Board (IAB), the In- For more information on IRTF, see ternet Engineering Task Force (IETF), the www.irtf.org. Internet Assigned Numbers Authority (IANA), and the Internet Research Task Internet Service Provider Abbreviated Force (IRTF). ISP. A company that provides commercial or residential customers access to the Internet For more information on ISOC, see via dedicated or dial-up connections. An ISP www.isoc.org. will normally have several servers and a internetwork Abbreviated internet. high-speed connection to an Internet back- Two or more networks using different bone. Some ISPs also offer Web site hosting services and free e-mail to their subscribers. networking protocols, connected by means of a router. Users on an internetwork can See also Internet Content Provider access the resources of all connected networks. Internet Society Abbreviated ISOC. An international organization that promotes Internetwork Operating System See cooperation and coordination for the Inter- Internetworking Operating System. 194 Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com
    • 2461book Page 195 Thursday, May 4, 2000 11:59 AM Internetwork Packet eXchange Internetworking Operating System Internetwork Packet eXchange Ab- Abbreviated IOS; sometimes referred to as breviated IPX. Part of Novell NetWare’s Internetwork Operating System Propri- native protocol stack, used to transfer data etary operating system software that runs between the server and workstations on the on the Cisco family of routers. network. IPX packets are encapsulated and carried by the packets used in Ethernet and IOS is stored in flash memory or in RAM in the frames used in Token Ring networks. the router and supports remote access and IPX packets consist of a 30-byte header protocol translation services, with connec- which includes the network, node, and tivity provided by terminals, modems, com- socket addresses for the source and the des- puters, printers, or workstations. LAN tination, followed by the data area, which terminal support includes Transmission can be from 30 bytes (only the header) to Control Protocol/Internet Protocol (TCP/ 65,535 bytes in length. Most networks im- IP) for telnet and rlogin connections to IP pose a more realistic maximum packet size hosts, tn3270 for connections to IBM hosts, of about 1500 bytes. and LAT (Local Area Transport) for con- The IPX packet header contains the follow- nections to DEC hosts. ing fields: For WANs, IOS supports connections over I Checksum For data integrity checking.. a dial-up line supporting AppleTalk Re- I Packet length Length of the packet in mote Access, Serial Line Internet protocol bytes (SLIP), Compressed SLIP (CSLIP), and I Transport control Number of routers a Point-to-Point protocol (PPP) and supports packet can cross before being discarded asynchronous terminal connections using terminal emulation software providing tel- I Packet type The service that created the packet net, rlogin, or IBM 3270 protocols. I Destination network Network address IOS also supports Simple Network Man- of the destination network agement Protocol (SNMP), Common Man- I Destination node Media access control agement Information Protocol/Common (MAC) address of the destination node Management Information Services (CMIP/ CMIS) and IBM’s Network Management I Destination socket Address of the pro- Vector Transport (NMVP) network man- cess running on the destination node agement systems. I Source network Network address of the source network You can configure IOS to control which networking protocols are routed, which I Source node Media access control protocols are used to do the actual routing, (MAC) address of the source node which interfaces on the router are used for I