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              Computer networks,
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             Standards for asynchronous
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               X.25 versus phone + modem
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                       National
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       National research computer networks:
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               International computer networks:...
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             Computer networks,
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                 The Internet
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                !! Task - Assignment !!

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        Host computers in the Internet:
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              Internet data communication
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                              TCP/IP
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                       TCP/IP:
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         Internet: addresses of computers
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                   Internet domain names
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       Internet: the basic methods to connect
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          Internet: trade offs in the basic
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                  Internet-assisted
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            Windows software versions:
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         Integrated Services Digital Network :
 ...
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       Money transfer via the networks:
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                 Dictionaries / glossarie...
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Computer networks, data communication and Internet

  1. 1. **** 1 Computer networks, data communication and Internet Introduction **** 2 Computer networks: summary The following gives an overview of computer networks and data communication: »The basic principles »Local area networks »National computers networks »International computer networks »The Internet »Future impact of digital communication networks
  2. 2. **** 3 Computer networks: prerequisites Before using computer networks, you should ideally have some knowledge and skills related to • computer hardware • computer software **** 4 Data communication: a definition • Interpersonal communication »Telecommunication —Broadcast —Telephone —Data communication –Remote login –File transfer –Hypertext transfer –Electronic mail
  3. 3. **-- 5 Data communication: various views User Sociologist (Applications) (Sociological aspects) Database producer Engineer (Information) (Techniques) **** 6 Data communication: which types of ‘data’? Linear text Sound Static images Hypertext Video Multimedia / Hypermedia Programs for computers Digital information 01
  4. 4. **-- 7 Telecommunication: digital versus analogue • Morse digital • Telephone analogue (or digital) • Data communication digital **** 8 Data communication: which types of ‘data’? • The same types of data (information) that can be stored and managed on a computer can be transferred over computer networks to one or several other computers. • So the networks form an important extension of the stand-alone computers. • “The network is the computer”
  5. 5. **** 9 Data communication: applications (Part 1) • Hard-copy transfer (Fax) • Online use of the processing power of a remote computer • Online access to information sources ! »library catalogues, »bookshop catalogues, »publisher’s catalogues, »campus-wide and community information systems, »(text or multimedia) databases, »network-based journals, ... **** 10 Data communication: applications (Part 2) • Software-downloading • Electronic mail from a person to one or several persons • Computer-network based interest groups • Online talking / chatting (IRC,...) • Video conferencing (Cu-seeme, ...) • Selling, shopping, buying,.. • ...
  6. 6. ***- 11 Computer network applications: information and communication 1-way = information transfer = almost no interaction • publications by e-mail / Internet radio • file transfer • (gopher) / core WWW based on http and static html pages • network services based on databases (input or searches) • e-mail communication / Usenet News • chat / telephony / video conferencing N-way = communication = highly interactive **-- 12 Computer networks: an analogy Traditional Networks • Letter • Hypermedia • Envelope • Protocol • Mail-box • Client • Post office • Server • Roads • Networks
  7. 7. **--Example 13 Computer network applications related to journalism • Journalists search for information online. • Publishers make the products of the journalists available online. • Journalists communicate with their readers by electronic mail. • ... ***- 14 Data communication: problems, difficulties, limitations • Low transfer speed • Technical complexity
  8. 8. ***- 15 Data communication: maximum transfer rate over dial-up lines 30000 28800 bits/s = bps 20000 10000 2400 0 0 100100100 300 300300 1200 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 **-- 16 ?? Question ?? What is the maximum speed of a modern modem? What is the maximum speed of a modern modem?
  9. 9. **-- 17 Standards for asynchronous communication over dial-up lines Maximum Standard Year Comment transmission speed by the of (in bps = bits / second) CCITT release 300 V21 1 200 V22 2 400 V22bis 9 600 V32 14 400 V32bis 28 800 V34 1995 33 600 V34 plus 1996 Made slower 56 000 V56 standards obsolete **** 18 Data communication: modems • description: MODulator-DEModulator: device to convert digital data signals into a suitable form for transmission along a telecommunications channel, and to convert them back upon receipt into machine readable form. • types »(Acoustic coupler) »Free standing box »Board/card to plug-in microcomputer
  10. 10. **-- 19 Data communication: transmission modes • Simplex Transmission in one way only • Half duplex Transmission in both directions, but not at the same time • Full duplex ! Transmission in both directions at the same time **-- 20 ?? Question ?? How long takes the transfer of the contents of a 200 page How long takes the transfer of the contents of a 200 page unformatted ASCII text document unformatted ASCII text document (like the text of a book for instance) (like the text of a book for instance) using data communication using data communication through the classical voice telecommunication network through the classical voice telecommunication network with a modern modem? with a modern modem? How did you estimate/calculate this value? How did you estimate/calculate this value?
  11. 11. ***- 21 ?? Question ?? How many characters (on average) How many characters (on average) could be received could be received when transfer speeds were when transfer speeds were maximum 300 bits/s, 28 800 bits/s? maximum 300 bits/s, 28 800 bits/s? Could the user read the incoming words well? Could the user read the incoming words well? **-- 22 Data-communication: Hard-copy transfer / Fax FAX FAX FAX FAX
  12. 12. ***- 23 Data communication: trade offs Cost LAN Dial-up/PAD (short distance) (low speed) Speed High volume Distance (high cost) **** 24 Computer network protocols: definition • When 2 computer systems communicate via network, they do that by exchanging messages. • The structure of network messages varies from network to network. • Thus the message structure in a particular network is agreed upon a priori and is described in a set of rules, each defined in a protocol.
  13. 13. *--- 25 Computer network protocols: Open Systems Interconnection The evolving international standard under development at ISO (International Standards Organization) for the interconnection of cooperative computer systems. An open system is one that conforms to OSI standards in its communications with other systems. **** 26 Computer networks, data communication and Internet Local Area Networks
  14. 14. **-- 27 A local area computer network: scheme **** 28 Data communication with a server in a Local Area Network • (Terminal) • Microcomputer with serial line Network communications software / server terminal emulation software • Microcomputer with network card and network software
  15. 15. ***- 29 ?? Question ?? Which applications Which applications do you know do you know of server computers of server computers in a Local Area Network (=LAN)? in a Local Area Network (=LAN)? ***- 30 Applications of server computers in a LAN • Extra personal disk space for the users • Common files with programs and/or data for many users (e.g. an intranet) • Making files available from the institute to external users over the Internet (e.g. using ftp, gopher, or http/WWW!) • Executing programs on a server in the LAN (e.g. using Unix or Windows NT or Windows 2000, in multi-tasking / multi-user mode) • Electronic mail servers; Usenet servers;...
  16. 16. ***- 31 ?? Question ?? Do you have access to a LAN Do you have access to a LAN in your organisation //institute //school //university? in your organisation institute school university? ***- 32 ?? Question ?? Do you have personal disk space available, Do you have personal disk space available, through the LAN of your institute? through the LAN of your institute?
  17. 17. **--Examples 33 LAN software packages for homogeneous networks: examples • Intel compatible processors: »LANtastic, »Novell, »Windows for Workgroups, Windows 95, Windows 98, Windows ME, Windows 2000, Windows XP... »... • Apple, ... ****Examples 34 LAN software packages for heterogeneous networks: examples Based on TCP/IP (protocol suite used in Internet) • For DOS: NCSA (= National Center for Supercomputing Applications) CUTCP, PC/NFS,... • For Windows 3.x: PC/NFS, PC/TCP, Trumpet TCP Manager,... • For Windows 95, 98,...: included! • For Windows NT, 2000,...: included!
  18. 18. ***- 35 ?? Question ?? Which basic network software Which basic network software can you use in your institute? can you use in your institute? ***- 36 Computer networks, data communication and Internet Packet switching
  19. 19. ***- 37 Packet switching in data communication networks: definition • Communication is not through a continuous stream of bits, but in small packets. • Routing, the followed route, may change during communication session. ***- 38 Packet switching in data communication networks: scheme = Computer = Computer = "Packet Switching Exchange" = "Packet Switching Exchange"
  20. 20. ***- 39 ?? Question ?? Which are the benefits offered Which are the benefits offered by packet switching? by packet switching? ***- 40 Packet switching in communications: advantages • Economic usage/exploitation of existing communication lines in the network, resulting in »less network congestion »higher data communication speed »lower cost • Less risk of interruptions due to breaks in a link of 2 nodes = higher reliability = less vulnerable • Possibility of error correction of individual packets
  21. 21. ***- 41 Packet switching protocols: examples • TCP/IP in the Internet • X-25 in OSI networks • ... **-- 42 The X.25 data communication protocol • protocol for packet switching in data network • an alternative to dial-up over voice telephone lines with modems • available in several “flavours”: »direct X.25 trunk connects over leased lines »through “PAD” interfaces »by ordinary dial-up modem access to X.25 “ports” Increasing quality
  22. 22. **-- 43 X.25 versus phone + modem for data communication Whether you use X.25 or phone plus modem depends on a number of factors; usually the determining factor is cost. »In North America, using a high speed modem over a telephone line tends to be less expensive. »In Europe, the phone system structure usually makes X.25 more cost- effective. **** 44 Computer networks, data communication and Internet National Wide Area Networks
  23. 23. **** 45 National Wide Area Networks • Public access national packet switching networks • Research computer networks • Public access made available by Internet Service Providers • ... **--Examples 46 National public access computer networks: examples • Belgium: DCS (Data Communication Service) • Nederland: Datanet • United Kingdom: PSS (Packet Switching Service) • France: Transpac • ...
  24. 24. ****Examples 47 National research computer networks: examples • Belgium: BELNET • Finland: FUNET • Germany: DFN • The Netherlands: Surfnet • United Kingdom: JANET (Joint Academic Network) • ... **** 48 Computer networks, data communication and Internet International computer networks
  25. 25. ****Examples 49 International computer networks: examples • National public data communication networks linked together • FidoNet • Bitnet / EARN • Usenet • Internet! • ... **-- 50 International connectivity map
  26. 26. **** 51 Computer networks, data communication and Internet The Internet data communication network **** 52 ?? Question ?? What is the Internet? What is the Internet?
  27. 27. **** 53 The Internet data communications network (Part 1) • “Internet” is not well-defined. • A network of smaller networks: The global collection of interconnected local area, regional and wide-area (national backbone) networks which use the TCP/IP suite of data communication protocols. @ **** 54 The Internet data communications network (Part 2) • Links computers of various types. • Is constantly growing. • The analogy of a superhighway has been used to describe the emerging system of networked computers. • The Internet has no owner, and is not managed by one organization. @
  28. 28. **-- 55 !! Task - Assignment !! Learn from the following training materials: Learn from the following training materials: Module 5: The Internet as an information resource. Module 5: The Internet as an information resource. Lesson 1: How the Internet works [online] Lesson 1: How the Internet works [online] Available from: Available from: http://www2.unescobkk.org/elib/publications/ictlip/module5/ http://www2.unescobkk.org/elib/publications/ictlip/module5/ [cited 2005]] [cited 2005 **** 56 The Internet: access from your Local Area Network Your microcomputer Local Area Network (LAN) One of the national networks The global Internet
  29. 29. **** 57 Host computers in the Internet: definition • A host (computer) is a domain name that has a unique IP address record associated with it. • Could be any computer connected to the Internet by any means. • For instance: www.vub.ac.be @ ***- 58 Data communication layer architecture User Application layer Transport layer Network layer Link layer
  30. 30. ***- 59 Internet data communication layers and protocols (Part 1) USER Application programs, using application protocols such as smtp, pop, imap, nntp, telnet, ftp, gopher, http... TCP = host to host transfer control protocol IP = Internet protocol different physical nets ***- 60 Internet data communication layers and protocols (Part 2) USER Client Server Computer Computer Client application programs Server application programs Application protocols Application protocols TCP TCP IP IP different physical nets
  31. 31. ***- 61 ?? Question ?? Why are most models/architectures Why are most models/architectures for data communication networks for data communication networks named named “layer models/architectures”? “layer models/architectures”? ***- 62 ?? Question ?? Which advantages are offered by Which advantages are offered by a layer architecture in a computer system? a layer architecture in a computer system?
  32. 32. ***- 63 ?? Question ?? Give some examples Give some examples of layer = onion skin of layer = onion skin architectures/models architectures/models in the area of information and communication technology, in the area of information and communication technology, and describe each layers briefly. and describe each layers briefly. **** 64 Transmission Control Protocol / Internet Protocol (TCP/IP) • the main suite of transport protocols used on the Internet for connectivity and transmission of data across heterogeneous systems • “glue that holds the Internet together” • an open standard • available on most Unix systems, VMS and other minicomputer systems, many mainframe and supercomputing systems and some microcomputer and PC systems
  33. 33. **-- 65 TCP/IP hardware The most common hardware system / solution used for actual physical connections using TCP/IP in a Local Area Network is Ethernet, but TCP/IP will also run on Token- Ring, serial lines (modems, serial connections) and other systems as well. ***- 66 !! Task - Assignment !! You can learn the basics of digital data communication You can learn the basics of digital data communication by looking at by looking at the video movie the video movie “Warriors of the net” [online] “Warriors of the net” [online] Available free of charge from: Available free of charge from: http://www.warriorsofthe.net/movie.html http://www.warriorsofthe.net/movie.html [cited 2005] [cited 2005]
  34. 34. **-- 67 TCP/IP: Serial Line Internet Protocol (SLIP) • SLIP is a standard on the Internet for RS232 serial line and modem connectivity between two systems. This allows any one SLIP client to connect to a SLIP server to provide connectivity between different IP hosts. • Both systems must have TCP/IP stacks running. • SLIP packages are available for PC systems. **-- 68 TCP/IP: Point to Point Protocol (PPP) • successor to SLIP • built in operating system software Windows 95,…
  35. 35. **-- 69 Internet application protocols / services based on the Internet (1) • telnet protocol for remote terminal login • ftp file transfer protocol • gopher communication using gopher menus • WAIS, Z39.50 for database searching • http hypertext transfer protocol (WWW) **-- 70 Internet application protocols / services based on the Internet (2) • smtp simple mail transfer protocol (e-mail) to send messages • pop post office protocol (e-mail) to read e-mail messages imap another protocol for reading e-mail messages • nntp network news transfer protocol in Usenet • ...
  36. 36. **** 71 Internet: addresses of computers with the Domain Name System • Internet style = Domain name system • The Internet naming scheme consists of a hierarchical sequence of names from the most specific to the most general (left to right), separated by dots. computer.subdomain.domain.(country if not USA) OR n1.n2.n3.n4 where n is a natural number (8-bit) ***-Examples 72 The Internet Domain Name System DNS: examples • Belgium: »ftp.vub.ac.be »www.vub.ac.be • U.S.A.: »dialog.com »ftp.cs.widener.edu
  37. 37. **-- 73 Internet domain names in the United States Most Internet sites in the US, Canada and US overseas installations follow a breakdown into six generic domains: »EDU: educational sites, such as universities »COM: commercial sites, generally large corporations »GOV: non-military government sites »MIL: military installations »ORG: non-commercial, non-network sites and gateways »NET: other networks to which e-mail must traverse a gateway ***- 74 !! Task - Assignment !! Read Read Brain, Marshall Brain, Marshall How domain name servers work. [online] How domain name servers work. [online] Available from: Available from: http://computer.howstuffworks.com/dns.htm http://computer.howstuffworks.com/dns.htm [cited 2005] [cited 2005]
  38. 38. **** 75 Internet: growth in number of hosts worldwide: linear plot 20000000 15000000 10000000 5000000 0 1993 1994 1995 1996 1997 1998 January of each year **-- 76 Internet: number of hosts 1991-1997 (plot downloaded from the net) Source: http://www.nw.com/ Source: http://www.nw.com/
  39. 39. **-- 77 Internet: number of hosts 1994-1998 (plot downloaded from the net) 40,000,000 New 35,000,000 survey Adjusted data 30,000,000 old survey 25,000,000 data 20,000,000 15,000,000 Source data: Source data: 10,000,000 M. Lottor M. Lottor Network Wizards Network Wizards 5,000,000 <www.nw.com> <www.nw.com> 0 Jan-94 Jan-95 Jan-96 Dec-96 Jan-98 Jan-99 Jan-00 ***- 78 Internet: the basic methods to connect (Part 1) • Method 1: Connect your computer to Increasing power Increasing power »the LAN of your institute, that includes a server computer connected to an Internet Service Provider, or »an Internet Service Provider, using a a cable modem + a public cable network • Method 2: Dial from your computer into an external Internet Service Provider, using a modem + the public voice telephone network • (Method 3: Connect your computer to an external Internet host that provides Internet services.)
  40. 40. ***- 79 Internet: the basic methods to connect (Part 2) Method 1: Increasing power Increasing power full-time Internet host Method 2: part-time Internet host (Method 3: using another Internet host) ***- 80 Internet: TCP/IP in the basic methods to connect Method 1: TCP/IP Increasing power Increasing power between your computer and the rest of the Internet, at high speed. Method 2: TCP/IP between your computer and the rest of the Internet, but speed limited by the modem and the telephone network (Method 3: TCP/IP between the Internet host you connect to and the rest of the Internet, but not between your computer and that Internet host.)
  41. 41. **-- 81 Internet: trade offs in the basic methods to connect Cost (SLIP or) PPP Shell-account on a server User interface Direct access Speed ***- 82 !! Task - Assignment !! You can learn the basics of Internet You can learn the basics of Internet online starting from online starting from http://www.bbc.co.uk/webwise/course/coursemenu.shtml http://www.bbc.co.uk/webwise/course/coursemenu.shtml
  42. 42. ***- 83 ?? Question ?? A way of describing the Internet is (select 1): A way of describing the Internet is (select 1): 1. A network of computers in an office, building or company 1. A network of computers in an office, building or company 2. An alternative to the telephone directory 2. An alternative to the telephone directory 3. A network of networks of computers that can "talk" to each other 3. A network of networks of computers that can "talk" to each other 4. An interconnected mess of computer cables 4. An interconnected mess of computer cables ***- 84 ?? Question ?? Who's in charge of the Internet? Who's in charge of the Internet? 1. Bill Gates 1. Bill Gates 2. No-one 2. No-one 3. The US senate 3. The US senate 4. The World-Wide Web 4. The World-Wide Web
  43. 43. ***- 85 ?? Question ?? The Internet is commonly referred to as (select 1): The Internet is commonly referred to as (select 1): 1. The Hard Drive 1. The Hard Drive 2. 2. The Net The Net 3. 3. The Waste of Time The Waste of Time 4. The Web 4. The Web **** 86 Internet Service Provider = ISP Internet Service Providers provide their clients access to Internet + in many cases »an email address / server »space for a web site »software tools to start »training »technical support »an accessible location for a WWW site of the client »assistance with WWW site design and promotion
  44. 44. ***- 87 ?? Question ?? What is an Internet Service Provider or ISP? (select 1) What is an Internet Service Provider or ISP? (select 1) 1. A company that allows access to their customers email messages 1. A company that allows access to their customers email messages 2. A company that provides an internet connection to its customers 2. A company that provides an internet connection to its customers 3. A company that provides internet connected computers 3. A company that provides internet connected computers 4. A company that maintains the structure of the internet 4. A company that maintains the structure of the internet **-- 88 ?? Question ?? How to select an How to select an Internet services/access provider? Internet services/access provider? How to evaluate How to evaluate Internet services/access providers? Internet services/access providers?
  45. 45. ***- 89 ?? Question ?? How are you connected How are you connected to the Internet? to the Internet? What is the name of What is the name of your Internet access provider? your Internet access provider? **-- 90 Internet end-user equipment Several types of equipment allow connection to Internet: • PC + Internet connection! • WebTV • Webphone = Screenphone (based on for instance JavaOS by Sun)
  46. 46. ***- 91 !! Task - Assignment !! Read Read Tyson, Jeff Tyson, Jeff How Internet infrastructure works. [online] How Internet infrastructure works. [online] Available from: Available from: http://computer.howstuffworks.com/internet-infrastructure.htm/printable http://computer.howstuffworks.com/internet-infrastructure.htm/printable [cited 2005] [cited 2005] **-- 92 The Core Internet and the Consumer Internet • Core Internet = all computers that can provide interactive Internet services (such as telnet, ftp, gopher, http,...) using server programs • Consumer Internet = all computers that can use interactive Internet services, using client programs (such as WWW browsers)
  47. 47. ***- 93 ?? Question ?? Being online means (select 1): Being online means (select 1): 1. You are connected to the internet 1. You are connected to the internet 2. Your computer is switched on 2. Your computer is switched on 3. You can read your email without paying phone costs 3. You can read your email without paying phone costs 4. All your computer files are organised in the right order 4. All your computer files are organised in the right order **-- 94 Internet: WAP = Wireless Application Protocol • A public/open, global specification that empowers mobile users with wireless devices to easily access and interact with information and services instantly over the Internet. • It allows to deliver and to access information evn when the full screen environment is either not available or not necessary.
  48. 48. **-- 95 Internet WAP: problems • Wireless devices represent the ultimate constrained computing device with limited CPU, memory, and battery life, and with only a simple user interface. • Wireless networks are constrained by low bandwidth, and unpredictable availability and stability. **-- 96 Internet WAP: the architecture
  49. 49. *--- 97 A network-based course about computer networks *--- 98 Internet in schools: aims and applications • Applications by the teachers. • Applications by the students. • + stimulates interest in information technology in general.
  50. 50. *--- 99 Internet-assisted teaching and learning: advantages (1) • For many people the learning materials are accessible fast and at low cost. (However, a version printed in multiple copies can be cheaper than a version printed by individual users.) The updates, corrections and improvements of the course material are accessible faster than when print is used for distribution. *--- 100 Internet-assisted teaching and learning: advantages (2) • Links to other Internet-based information sources can be offered in the course material, better than in a printed course. • Permanent self assessment by students can work better than with printed course material.
  51. 51. *--- 101 Internet-assisted teaching and learning: advantages (3) • Communication students - professor - teaching assistant(s) - administration/secretariat can be offered, based on an e-mail group, a Usenet Newsgroup or a web-based group, for each course. Furthermore, an archive of messages can be stored and can be made searchable. In this way one can save time and costs related to travel to a classroom and communication is not limited to fixed contact hours. *--- 102 Internet-assisted teaching and learning: advantages (4) • Multimedia (coloured graphics, sound, animations, video,...) can be integrated well in the course material.
  52. 52. *--- 103 Internet-assisted teaching and learning: advantages (5) • To create a better social environment for study, professors as well as students can make information about themselves available through the web for the students. • Adaptive hypertext is possible, but more complicated to develop. *--- 104 Internet-assisted teaching and learning: limitations • Students should have access to a suitable computer and to Internet at an acceptable price. • The contents of the computer-based course should be easily conveyable without personal contacts and practical work. • Interactive work that requires real-time access to the server computer can be too expensive due to the telecommunication cost.
  53. 53. **-- 105 Windows software versions: their suitability for Internet usage Windows Windows 3.x 95, 98, ME, 2000, XP… Licensing fee / price / costs Lower! Higher RAM required Less! More Includes TCP/IP stack No Yes! Set-up of Internet applications Less easy Easier! Allows (faster) 32-bit programs No Yes! Problems with limitations of Many Few! Windows “resources” ***- 106 Computer networks, data communication and Internet Miscellany
  54. 54. ***- 107 Integrated Services Digital Network : What is it? • Integrated Services Digital Network = ISDN • intended as a worldwide upgrade to digital status for the Public Switched Telephone Network • 64 kbits/s up to 2 Mbits/s available (which is higher than with a modem) • designed to be delivered over existing copper wires • allows simultaneous transfer of sound, text and numbers, graphics (fax),... **-- 108 Integrated Services Digital Network : applications • backup of leased lines • interconnection of LANs • home-office use • home use: telephone, fax, network access,... • supporting existing analogue equipment if necessary • ...
  55. 55. ***- 109 Money transfer via the networks: increasing importance • Money transfer over the Internet and public access networks is not secure without precautions. • Several systems will allow secure money transfer, even for small amounts of money, with only small transfer costs: “Digital cash”, “Cyberbucks”,... ***- 110 Money transfer via the networks: impact on services offered • Many services and sources of information, offered free of charge previously, may start charging money. • Many services and sources of information, which were previously not offered, because there was no good charging and paying mechanism available, may be offered at a price.
  56. 56. ***- 111 Dictionaries / glossaries about networks and Internet • Available online free of charge: http://dir.yahoo.com/Computers_and_Internet/Internet/Dictionaries/ ***- 112 !? Question !? Which ways of data communication Which ways of data communication do you know do you know to access online information systems? to access online information systems?
  57. 57. **** 113 Microcomputer -- external computer: some ways of data communication Tele- Voice telecommunication network Micro- Modem phone computer ISDN TelePAD LAN Public data comm. network Local External Gateway computer system computer PAD Private/academic data comm. network (e.g. Internet) Leased, fixed communication line Intern Extern ***- 114 Computer networks, data communication and Internet The future impact of digital communication networks
  58. 58. ***- 115 Future impact of digital communication networks Extreme scenarios: • Boom scenario: evolution to ‘computopia’ • Doom scenario: evolution to a digital ‘brave new world’ ***- 116 Computer-based communication: boom scenario Evolution to ‘computopia’ • International, interpersonal communication increases, using the international computer communication networks. • Information gap (between information rich and information poor) disappears: access from everywhere (even from developing countries) to internationally available information. • Capitalism and repression disappear.
  59. 59. ***- 117 Computer-based communication: doom scenario Evolution to a digital ‘brave new world’ • Face-to-face, interpersonal communication disappears. • Information gap (between information rich and information poor) becomes larger. • Capitalism uses the evolving techniques for increased control and repression. ***- 118 The world of information from your desktop
  60. 60. **-- 119 Computer networks, data communication and Internet Data transfer rate between components of computer systems **-- 120 Data transfer rates: introduction • The speed of delivery of information = data transfer rate. • This is always limited by the weakest component. • High quality graphics, audio, animation, video,… typically require a high transfer speed. • When a transfer system (medium, channel,…) is used (shared) by more than one user, the effective, practical transfer rate decreases of course.
  61. 61. **-- 121 ?? Question ?? Compare transfer rates Compare transfer rates in computer networks in computer networks with the transfer rates with the transfer rates of CD-ROM systems. of CD-ROM systems. **-- 122 Data transfer rate of various computer systems/media Type Transfer rate 14.4 kbits/s modem 1.8 KB/s 28.8 kbits/s modem 3.6 KB/s ISDN 7-16 KB/s T1 Internet line 30 –200 KB/s 1x CD-ROM 150 KB/s Ethernet 1 000 KB/s 24x CD-ROM 3 600 KB/s USB 12 000 KB/s
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