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Computer Networks Foundation - Study Notes
These study notes focus on computer networks and are tailored for women, though men can also benefit. The content covers networking basics, types of networks, the OSI model, networking devices, topologies, physical media, and practical installation tools. The document aims to empower women in technology by enhancing their skills and knowledge in networking.
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Computer Networks Foundation - Study Notes
- 1. Computer Networks Foundation StudyNotes +W Series - Technology Skills For Women1 http://SlideShare.net/OxfordCambridge 1 Men are allowed to read too, if they wish, as the language style and the document format are universal.
- 2. Study Notes http://SlideShare.net/OxfordCambridge 2| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Table of Contents About “+W Series - Technology Skills For Women”..............................................................................................................................................5 References.................................................................................................................................................................................................................................6 Course Objectives..................................................................................................................................................................................................................7 I. NETWORKING BASICS:...........................................................................................................................................................8 A. NETWORKING OVERVIEW..............................................................................................................................................................................9 1. Core network components...........................................................................................................................................................................................9 Quiz............................................................................................................................................................................................................................................ 11 2. Network architectures................................................................................................................................................................................................ 11 Quiz............................................................................................................................................................................................................................................ 13 Quiz............................................................................................................................................................................................................................................ 13 Summary................................................................................................................................................................................................................................. 13 B. TYPES OF NETWORKS..................................................................................................................................................................................14 1. Local area networks (LANs)..................................................................................................................................................................................... 14 Quiz............................................................................................................................................................................................................................................ 15 2. Wide area networks (WANs)................................................................................................................................................................................... 15 Quiz............................................................................................................................................................................................................................................ 16 Quiz............................................................................................................................................................................................................................................ 17 3. Metropolitan area networks (MANs)................................................................................................................................................................... 17 Quiz............................................................................................................................................................................................................................................ 17 4. Intranets and extranets .............................................................................................................................................................................................. 18 Quiz............................................................................................................................................................................................................................................ 18 Quiz............................................................................................................................................................................................................................................ 19 Summary................................................................................................................................................................................................................................. 19 C. THE OSI MODEL ..........................................................................................................................................................................................20 1. The OSI reference model............................................................................................................................................................................................ 20 Quiz............................................................................................................................................................................................................................................ 22 2. Layers of the OSI model.............................................................................................................................................................................................. 23 Quiz............................................................................................................................................................................................................................................ 26 3. Encapsulation and de-encapsulation................................................................................................................................................................... 26 Quiz............................................................................................................................................................................................................................................ 30 4. The TCP/IP stack........................................................................................................................................................................................................... 34 Quiz............................................................................................................................................................................................................................................ 37 Quiz............................................................................................................................................................................................................................................ 38 Summary................................................................................................................................................................................................................................. 39 D. UNDERSTANDING BASIC NETWORKING CONCEPTS.................................................................................................................................40 Exercise overview.............................................................................................................................................................................................................. 40 Task 1: Identifying networks........................................................................................................................................................................................ 40 Step 1 of 3............................................................................................................................................................................................................................... 41 Result........................................................................................................................................................................................................................................ 41 Step 2 of 3............................................................................................................................................................................................................................... 41 Result........................................................................................................................................................................................................................................ 41 Step 3 of 3............................................................................................................................................................................................................................... 42 Result........................................................................................................................................................................................................................................ 42 Task 2: Identifying characteristics of data encapsulation .............................................................................................................................. 42 Step 1 of 3............................................................................................................................................................................................................................... 43 Result........................................................................................................................................................................................................................................ 43 Step 2 of 3............................................................................................................................................................................................................................... 44 Result........................................................................................................................................................................................................................................ 44 Step 3 of 3............................................................................................................................................................................................................................... 44 Result........................................................................................................................................................................................................................................ 45 II. NETWORKING DEVICES AND TOPOLOGIES:.................................................................................................................46 E. COMPONENTS OF A NETWORK PC............................................................................................................................................................47 1. PC components............................................................................................................................................................................................................... 47 Quiz............................................................................................................................................................................................................................................ 53 2. Network interface cards............................................................................................................................................................................................. 54 Quiz............................................................................................................................................................................................................................................ 57 Quiz............................................................................................................................................................................................................................................ 57 Summary................................................................................................................................................................................................................................. 58
- 3. Study Notes http://SlideShare.net/OxfordCambridge 3| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n F. NETWORK DEVICES.....................................................................................................................................................................................59 1. OSI layer 1 devices........................................................................................................................................................................................................ 60 Quiz............................................................................................................................................................................................................................................ 61 2. OSI layer 2 devices........................................................................................................................................................................................................ 61 Quiz............................................................................................................................................................................................................................................ 65 3. OSI layer 3 devices........................................................................................................................................................................................................ 65 Quiz............................................................................................................................................................................................................................................ 70 4. Multiple layer devices.................................................................................................................................................................................................. 70 Quiz............................................................................................................................................................................................................................................ 73 Quiz............................................................................................................................................................................................................................................ 73 Summary................................................................................................................................................................................................................................. 73 G. NETWORK TOPOLOGIES..............................................................................................................................................................................74 1. Distinguishing physical and logical topologies............................................................................................................................................... 74 Quiz............................................................................................................................................................................................................................................ 76 2. Identifying topology types ........................................................................................................................................................................................ 77 Quiz............................................................................................................................................................................................................................................ 81 Quiz............................................................................................................................................................................................................................................ 81 Summary................................................................................................................................................................................................................................. 81 H. IDENTIFYING NETWORK DEVICES AND TOPOLOGIES..............................................................................................................................82 Exercise overview.............................................................................................................................................................................................................. 82 Task 1: Identifying network device functions...................................................................................................................................................... 82 Step 1 of 3............................................................................................................................................................................................................................... 83 Result........................................................................................................................................................................................................................................ 83 Step 2 of 3............................................................................................................................................................................................................................... 84 Result........................................................................................................................................................................................................................................ 84 Step 3 of 3............................................................................................................................................................................................................................... 84 Result........................................................................................................................................................................................................................................ 84 Task 2: Selecting network topologies....................................................................................................................................................................... 85 Step 1 of 3............................................................................................................................................................................................................................... 85 Result........................................................................................................................................................................................................................................ 86 Step 2 of 3............................................................................................................................................................................................................................... 86 Result........................................................................................................................................................................................................................................ 86 Step 3 of 3............................................................................................................................................................................................................................... 87 Result........................................................................................................................................................................................................................................ 87 III. PHYSICAL MEDIA: .............................................................................................................................................................89 I. NETWORK CABLING AND WIRELESS MEDIA.............................................................................................................................................90 1. Unshielded and shielded twisted pair cable..................................................................................................................................................... 90 Quiz............................................................................................................................................................................................................................................ 93 2. Coaxial cable..................................................................................................................................................................................................................... 94 Quiz............................................................................................................................................................................................................................................ 97 3. Fiber optic cable............................................................................................................................................................................................................. 97 Cable types...........................................................................................................................................................................................................................101 Quiz..........................................................................................................................................................................................................................................102 4. Wireless communications.......................................................................................................................................................................................102 Complete list of cable types.........................................................................................................................................................................................106 Quiz..........................................................................................................................................................................................................................................106 Summary...............................................................................................................................................................................................................................107 J. NETWORK CABLE CONNECTORS..............................................................................................................................................................108 1. Twisted pair and coaxial cable connectors.....................................................................................................................................................108 Quiz..........................................................................................................................................................................................................................................113 2. Fiber optic cable connectors..................................................................................................................................................................................114 Quiz..........................................................................................................................................................................................................................................116 3. The IEEE 1394 standard ..........................................................................................................................................................................................117 Quiz..........................................................................................................................................................................................................................................118 Summary...............................................................................................................................................................................................................................119 K. NETWORK INSTALLATION TOOLS............................................................................................................................................................120 1. Patch panels and wiring tools................................................................................................................................................................................120 Quiz..........................................................................................................................................................................................................................................123 2. Media testing tools......................................................................................................................................................................................................123 Quiz..........................................................................................................................................................................................................................................128 Summary...............................................................................................................................................................................................................................128 L. CONNECTING THE NETWORK (EXERCISE).............................................................................................................................................130 Exercise overview............................................................................................................................................................................................................130 Task 1: Choosing a network media type ...............................................................................................................................................................130
- 4. Study Notes http://SlideShare.net/OxfordCambridge 4| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Step 1 of 1.............................................................................................................................................................................................................................131 Result......................................................................................................................................................................................................................................131 Task 2: Recognizing media specifications............................................................................................................................................................132 Step 1 of 3.............................................................................................................................................................................................................................132 Result......................................................................................................................................................................................................................................133 Step 2 of 3.............................................................................................................................................................................................................................133 Result......................................................................................................................................................................................................................................133 Step 3 of 3.............................................................................................................................................................................................................................134 Result......................................................................................................................................................................................................................................134 Task 3: Recognizing cable connector types.........................................................................................................................................................135 Step 1 of 4.............................................................................................................................................................................................................................135 Result......................................................................................................................................................................................................................................135 Step 2 of 4.............................................................................................................................................................................................................................136 Result......................................................................................................................................................................................................................................136 Step 3 of 4.............................................................................................................................................................................................................................137 Result......................................................................................................................................................................................................................................137 Step 4 of 4.............................................................................................................................................................................................................................137 Result......................................................................................................................................................................................................................................138 IV. ANNEXES: ..........................................................................................................................................................................139 The OSI model Illustrated.............................................................................................................................................................................................140 M. GLOSSARY ...................................................................................................................................................................................................143 N. ANSWERS TO QUIZZES..............................................................................................................................................................................166
- 5. Study Notes http://SlideShare.net/OxfordCambridge 5| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n About “+W Series - Technology Skills For Women” Study Notes in the field of technology will be put together under this category for the following reasons: to encourage ladies, who wish to do so, to stand up and look over the fence into technology related topics; with no apprehension or fear; and perhaps consider embracing a career move into a technological path; or simply as to broaden their general knowledge; after all ICT is in most aspects of everyday life; no matter the decision, their skills, professional strengths, and contribution can only be something positive for technical and technological fields. Enjoy!
- 6. Study Notes http://SlideShare.net/OxfordCambridge 6| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n References Network + Study Guide, David Groth, Sybex Inc OSI model (Open Systems Interconnection model), http://en.wikipedia.org/wiki/OSI_model , on 18 April 2014 at 11:00 Computo integrado, http://avecomputointe.blogspot.fr/2012_02_01_archive.html , February 2012
- 7. Study Notes http://SlideShare.net/OxfordCambridge 7| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Computer Networks Foundation I. Networking basics: A. Networking overview B. Types of networks C. The OSI model D. Understanding basic networking concepts II. Networking devices and topologies: E. Components of a network PC F. Network devices G. Network topologies H. Identifying network devices and topologies III. Physical media: I. Network cabling and wireless media J. Network cable connectors K. Network installation tools L. Connecting the network Course Objectives Topic Name When you have completed this topic, you should be able to Networking overview identify the primary components of a network and distinguish between the two main network architectures. Types of networks distinguish between the main types of networks The OSI model distinguish between the OSI reference model and the TCP/IP stack. Understanding basic networking concepts distinguish between common network categorizations and identify the characteristics of data encapsulation. Components of a network PC identify the major components of a network PC and list the resources required to install a NIC. Network devices identify the functions, features, and operation of network devices used at different layers of the OSI model. Network topologies distinguish between different network topologies Identifying network devices and topologies match network devices to their functions and distinguish between different network topologies. Network cabling and wireless media differentiate between types of network media. Network cable connectors recognize the types of cable connectors used in modern networks. Network installation tools determine the most appropriate network tool to use in a given scenario. Connecting the network determine the appropriate network media and connectors to use in a given scenario.
- 8. Study Notes http://SlideShare.net/OxfordCambridge 8| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n I. Networking basics: A. Networking overview B. Types of networks C. The OSI model D. Understanding basic networking concepts After completing this section, you should be familiar with: identifying the primary components of a network and distinguish between the two main network architectures distinguishing between the main types of networks
- 9. Study Notes http://SlideShare.net/OxfordCambridge 9| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n A. Networking overview After completing section, you should be able to identify the primary components of a network and distinguish between the two main network architectures. 1. Core network components 2. Network architectures | 1. Core network components A network consists of two or more computers connected together which share resources such as data, printers, and an Internet connection. The term "networking" refers to the sharing of resources on a network. Networks can consist of a small group of computers localized to a building or they can extend over large geographic areas, as follows. local area network (LAN) wide area network (WAN)
- 10. Study Notes http://SlideShare.net/OxfordCambridge 10| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n local area network (LAN) A LAN is a network that is confined to a small geographic area – for example, within a building. Each individual computer can access data and devices anywhere on the LAN. wide area network (WAN) A WAN is a computer network that spans a relatively wide area. A WAN consists of a system of interconnected LANs. The Internet is an example of a global WAN. A network consists of the following three primary components. Server Workstation Host Server A server is a powerful computer that provides resources to other computers on the network. Servers are often dedicated, meaning that they perform no other tasks besides their server tasks. Workstation
- 11. Study Notes http://SlideShare.net/OxfordCambridge 11| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n A workstation is any computer on a network that can request resources and is used to do work. A workstation may have multiple CPUs, making it faster and more capable than a personal computer. Workstations and clients are different. A client is any device on a network that can request resources. Host A host is any network device that has a Transmission Control Protocol/Internet Protocol (TCP/IP) address. Workstations and servers that have TCP/IP addresses can be considered hosts. Each host has a unique IP address. Quizi Match each network component with its description. Options: 1. Host 2. Server 3. Workstation Targets: A. A powerful computer that provides resources to other computers on the network B. Any computer on a network that can request resources and is used to do work C. Any network device that has a TCP/IP address 2. Network architectures The purpose of a network is to share resources. The following are two common network types. Peer-to-peer Client/server Peer-to-peer In a peer-to-peer network, the computers have no centralized authority. All of the computers have server and client capabilities and equal responsibilities on the network. Access rights to resources in a peer-to- peer network are handled by the machine holding the resource. Peer-to-peer networks are generally used in situations where security needs are minimal.
- 12. Study Notes http://SlideShare.net/OxfordCambridge 12| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Client/server With the client/server model, the entire network is managed from a central point and some computers are dedicated to serving the others. Each computer is either a client or a server and each client relies on a server for resources. The Internet is based on the client/server model. Client/server networks hold several advantages over peer-to-peer networks. A client/server network is more organized than a peer-to-peer network, because all files and resources are stored on servers and are easier to locate. Client/server networks are more secure than peer-to-peer networks, because passwords and usernames are stored on a dedicated server. Unlike peer-to-peer networks, client/server networks can be scaled almost infinitely in size.
- 13. Study Notes http://SlideShare.net/OxfordCambridge 13| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Quizii What are the characteristics of the client/server network model? Options: 1. Centralized management 2. Clients have server functionality 3. Good security 4. Scalability Quiziii What are the advantages of using a client/server network over a peer-to-peer network? Options: 1. Access rights handled by clients 2. Easier to manage 3. More efficient 4. More secure Summary A network is made up of two or more computers linked together. Networking is the term used to refer to the sharing of resources on the network. Networks can vary in size from local area networks (LANs), which are contained in a building, to wide area networks (WANs), such as the Internet. The three primary components of a network are a server, a workstation, and a host. Two of the most common network types are client/server and peer-to-peer. Peer-to-peer networks have no centralized authority while client/server networks are managed from a centralized point. Client/server networks have several advantages over peer-to-peer networks such as ease of management and better security.
- 14. Study Notes http://SlideShare.net/OxfordCambridge 14| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n B. Types of networks After completing this section, you should be able to distinguish between the main types of networks. 1. Local area networks (LANs) 2. Wide area networks (WANs) 3. Metropolitan area networks (MANs) 4. Intranets and extranets 1. Local area networks (LANs) Local area networks (LANs) are one of the most widely used types of networks. LANs are high-speed, low-error, data networks that are confined to a small area, usually within a building. LANs connect workstations, servers, and peripheral devices, such as printers, together. Ethernet LANs are the most common type of LANs. This term is often used to refer to all types of LANs. Different types of Ethernet LAN are Ethernet Fast Ethernet Gigabit Ethernet Network standards are defined by the Institute of Electrical and Electronics Engineers (IEEE).
- 15. Study Notes http://SlideShare.net/OxfordCambridge 15| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n In the middle of the 1980s, an IEEE workgroup defined a standard for Ethernet called Ethernet 802.3. Today, this standard is commonly referred to as Ethernet. Quiziv Identify the correct statement about a LAN. Options: 1. Limited to a specific area 2. Covers a large geographic area 3. Can only be a client/server network 4. Not scalable 2. Wide area networks (WANs) A wide area network, or WAN, is a network that covers a large geographic area. WANs can operate beyond the geographic scope of a LAN. The Internet is the best known example of a WAN. The Internet is public but WANs can also be private, linking the worldwide locations of a corporation together, for example. WANs differ from LANs in a number of ways: they cover greater distances than LANs WAN speeds are slower LANs primarily use private network transports while WANs can use public or private network transports
- 16. Study Notes http://SlideShare.net/OxfordCambridge 16| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Internet service providers, or ISPs, are used to facilitate the large geographic reach of a WAN. If a corporation wanted to link up its American headquarters with its European office, it would use an ISP to establish the network over this great distance. WANs require several core devices to function. Routers WAN switches Modems Routers Routers are used to direct traffic on a network to its correct destination. A router is connected to at least two networks, and it is located where the networks connect. WAN switches WAN switches are used to logically connect routers on the WAN using virtual circuits. Modems Modems provide remote access to networks by converting digital signals to analog ones so that the data can be transmitted over analog communication facilities such as telephone lines. Quizv In what ways do WANs differ from LANs?
- 17. Study Notes http://SlideShare.net/OxfordCambridge 17| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Options: 1. Cover large geographic areas 2. Only connect cities together 3. WAN connections are more expensive than LAN connections 4. WANs primarily use private network transports Quizvi Match each WAN device to its function. Options: 1. Modem 2. Router 3. WAN switch Targets: A. Directs traffic on a network to the correct destination B. Connects routers on a WAN C. Provides remote access to a network 3. Metropolitan area networks (MANs) A metropolitan area network, or MAN, is a network that covers a metropolitan area such as a city or suburban area. MANs are larger than LANs but smaller than WANs. A MAN is usually created when two or more LANs are connected together, offering high-speed connections. Quizvii Which statement correctly describes a MAN?
- 18. Study Notes http://SlideShare.net/OxfordCambridge 18| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Options: 1. Connects workstations, peripherals, terminals, and other devices in a single building 2. Interconnected by routers and other devices and functions as a single global network 3. Serves users across a wide geographic area 4. Spans a metropolitan area such as a city or suburban area 4. Intranets and extranets An intranet is a private network that exists within a business. It can consist of many interlinked LANs. Only people within the company or organization can access the intranet. The main purpose of an intranet is to share company information and resources between employees. An intranet looks like a private version of the Internet. When part of a company's intranet becomes available to customers, suppliers, or anyone outside the company, the network is known as an extranet. Extranets use Internet Protocol (IP) and a public communication system to share part of an organization's information and resources with its customers, suppliers, or other businesses. A firewall is used to ensure security on the network. Quizviii Identify the features of extranets. Options: 1. Available to users outside the business 2. Available only within a business
- 19. Study Notes http://SlideShare.net/OxfordCambridge 19| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n 3. Requires security Quizix Match each network type to its description. Options: 1. LAN 2. MAN 3. WAN Targets: A. Covers a city or suburban area B. Confined to a small area C. Covers a large geographic area Summary A local area network (LAN) is used to connect workstations, servers, and peripheral devices, such as printers, together. It is confined to a small area, usually within a building. A wide area network (WAN) covers a large geographic area. WANs can be public or private. WANs have slower connection speeds than LANs. WANs use routers, WAN switches, and modems. The Internet is an example of a global WAN. A metropolitan area network (MAN) extends across a city or a large suburban area. A MAN develops when two or more LANs are connected together. An intranet is a private network contained inside a company. It can contain many LANs linked together. It allows employees to share information and access company resources. An extranet is part of a company's intranet that can be accessed by anyone outside the company.
- 20. Study Notes http://SlideShare.net/OxfordCambridge 20| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n C. The OSI model After completing this topic, you should be able to distinguish between the OSI reference model and the TCP/IP stack. 1. The OSI reference model 2. Layers of the OSI model 3. Encapsulation and de-encapsulation 4. The TCP/IP stack 1. The OSI reference model The Open System Interconnection (OSI) model was developed in 1984 by the International Organization for Standardization (ISO) to resolve the problem of incompatible networks. There had been a big increase in the number and sizes of networks in the middle of the 1980s. Companies began to experience difficulties due to all the expansions they had made as a result of the early development of LANs, MANs, and WANs. Many companies could not communicate with each other because they were using different network specifications and implementations. They realized that the proprietary technologies, which were privately developed, owned, and controlled by individual or a group of companies, were a hindrance to developing networking systems. A standard or a technology can be described as follows. proprietary open
- 21. Study Notes http://SlideShare.net/OxfordCambridge 21| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n proprietary A proprietary standard means that one company (or a small group of companies) controls the technology rights and usage. Proprietary is the opposite to open when referring to standards or technologies in the computer industry. open An open standard means that the technology usage is available for free implementation to the public. The ISO researched different network schemes and proposed a seven-layer model.
- 22. Study Notes http://SlideShare.net/OxfordCambridge 22| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n The OSI model is a reference model for describing how information should be exchanged between points on a network. For example, it describes how data from a word processing application on one computer is sent to another computer when the sender and receiver are connected using different network media. The OSI model has a number of advantages: enables compatibility between different types of networks provides like standards for vendors facilitates an understanding of how data travels within a network enables compatability between different types of networks The OSI model enables greater compatibility and interoperability between the different network technologies produced by companies around the world. provides like standards for vendors The OSI model provides vendors with a set of standards that enables them to implement compatible networks. facilitates an understanding of how data travels within a network Many network vendors relate their products to the OSI model, especially when they want to educate customers on the use of their products. It is considered as a standard for teaching people about sending and receiving data on a network. Quizx Identify the true statements about the OSI model.
- 23. Study Notes http://SlideShare.net/OxfordCambridge 23| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Options: 1. Facilitates compatibility between different networks 2. Specifies how information travels through networks 3. Speeds up network communication 4. Defines the network functions that occur at each layer 2. Layers of the OSI model The process of data transfer between computers is represented by the seven layers of the OSI model - each of which addresses an essential networking task. The OSI model is divided into seven numbered layers. The layers are: application presentation session transport network data-link physical
- 24. Study Notes http://SlideShare.net/OxfordCambridge 24| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n application The application layer provides file, print, message, and application database services. It provides network services to applications that require access to the network. It controls how these services are advertised and made available. It does not provide services to any other layer. This layer also deals with user authentication and privacy. presentation The presentation layer manages data representation. It transforms data into a mutually agreed format that each application can understand. It formats and structures data, ensuring it is readable between hosts. An example of this would be the implementation of character sets such as the American Standard Code for Information Interchange (ASCII) and Extended Binary-Coded Decimal Interchange Code (EBCDIC). It also organizes the syntax of data transfer for the application layer. Data compression and encryption take place at this layer. session The session layer provides communication between hosts. It does this by connection establishment, data transfer, and connection release. This includes the authentication, creation, management, and termination of sessions between different applications. It provides its services to the presentation layer. transport The transport layer aids point-to-point communications. It provides reliability in the transportation of data between hosts and ensures complete data transfer. The transport layer uses error detection and recovery information flow control to establish, maintain, and terminate all virtual circuits. network The network layer ensures data delivery by providing connectivity and path selection between two host systems. It selects the most appropriate path for sending data, and routes data packets. In the network layer, logical addressing and resolving names to host physical addresses is carried out. This layer works with the commonly used IP addresses assigned to hosts. The network layer provides logical LAN-to-LAN communications by supporting the routing of data between different networks. data-link The data-link layer arranges bits from the physical layer into logical chunks of data, known as frames. A frame is a contiguous series of data with a common function. Framing enables the network to organize bits into a logical data format and send them to the correct computer. This layer also controls how data is formatted and how transmission on the network is controlled. physical The physical layer is responsible for providing the most basic element of data transport – binary transmission. This layer outlines the functional, procedural, electrical, and mechanical specifications for controlling physical links. The specifications relate to the activation, maintenance, and deactivation of physical links. It also controls the transmitting of data onto physical media. Each layer in the OSI model contains a set of functions or protocols performed by programs to enable data packets to travel from A to B on a network. The protocols that operate at each layer offer a solution to a networking challenge. The OSI model is conceptualized in a way that may seem upside down. Data is received from the
- 25. Study Notes http://SlideShare.net/OxfordCambridge 25| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n network and sent up from the physical layer at the bottom to the application layer - which, in turn, sends data it generates back down through the layers. When it reaches the physical layer again, it is sent out on the network. The advantages of layering network functions are: accelerates evolution ensures interoperable technology facilitates modular engineering reduces complexity standardizes interfaces simplifies teaching and learning accelerates evolution Layering accelerates evolution by supporting updates and improvements to individual components. It can do this without affecting other components or having to rewrite the entire protocol. ensures interoperable technology Layering ensures interoperable technology and quicker development by preventing changes in one layer from affecting the other layers. facilitates modular engineering Layering facilitates modular engineering by allowing different types of network hardware and software to communicate with each other.
- 26. Study Notes http://SlideShare.net/OxfordCambridge 26| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n reduces complexity Layering reduces complexity by breaking network communication into smaller, simpler components. standardizes interfaces Layering standardizes network component interfaces, which provides vendors with a set of standards that ensures greater compatibility between the various network technologies. simplifies teaching and learning Layering simplifies teaching and learning by breaking up the task of networking into a number of distinct layers. Quizxi Match these OSI layers to a description of their functions. Options: 1. Application 2. Data-link 3. Network 4. Presentation 5. Session 6. Transport Targets: A. Ensures data delivery B. Ensures reliable data transfer between hosts C. Formats and structures data D. Synchronizes and maintains communication between hosts E. Provides access to the network media F. Provides network services to applications 3. Encapsulation and de-encapsulation When one computer wants to send data to another computer, the data must first be packaged through a process called encapsulation. Encapsulation wraps the data with the required protocol information before transmitting the data to the network.
- 27. Study Notes http://SlideShare.net/OxfordCambridge 27| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Encapsulation can be compared to placing a letter in an envelope, then writing the name and address on it so that it can be delivered to the right destination.
- 28. Study Notes http://SlideShare.net/OxfordCambridge 28| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n As data moves through the layers of the OSI model, each layer adds a header (and a trailer, if applicable). The process starts at the application layer and moves down to the physical layer. These headers and trailers contain information for devices and receiving hosts to ensure that the data is delivered reliably. They also ensure that the receiver can understand and use that data accordingly. These are the eight steps in the encapsulation process: step 1 step 2 step 3 step 4 step 5 step 6 step 7 step 8
- 29. Study Notes http://SlideShare.net/OxfordCambridge 29| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n step 1 The user data is sent from an application to the seventh layer of the OSI model - the application layer. step 2 The application layer adds the header (L7) to the user data. The L7 header and the original user data become the data that is now passed down to the presentation layer. step 3 The presentation layer adds the presentation layer header (L6) to the data. This now becomes the data that is passed down to the session layer. step 4 The session layer adds the session layer header (L5) to the data. This now becomes the data that is passed down to the transport layer. step 5 The transport layer adds the transport layer header (L4) to the data. This now becomes the data that is passed down to the network layer. step 6 The network layer adds the network layer header (L3) to the data. This now becomes the data that is passed down to the data-link layer. step 7
- 30. Study Notes http://SlideShare.net/OxfordCambridge 30| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n The data-link layer adds the data-link layer header (L2) to the data. This now becomes the data that is passed down to the physical layer. step 8 The last layer of the OSI model - the physical layer - then transmits the bits onto the network media. Quizxii Rank the layers of the OSI model in the order in which encapsulation occurs, after the data first passes through the application layer. Option Description A Data-link B Network C Physical D Presentation E Session F Transport De-encapsulation occurs when information is received - first it is checked for errors and, if none is found, it is then stripped of its header. The physical layer passes the frame to the data-link layer for manipulation - this process can be divided into four tasks within the data-link layer.
- 31. Study Notes http://SlideShare.net/OxfordCambridge 31| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n De-encapsulation is similar to checking the address on a letter to see if it's for you or not, then removing the letter from the envelope if it's addressed to you. The data-link layer performs the following tasks in the de-encapsulation process:
- 32. Study Notes http://SlideShare.net/OxfordCambridge 32| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n task 1 task 2 task 3 task 4 task 1 It checks the data-link trailer to see if the data contains any errors. task 2 If the data contains any errors, it may be discarded - the data-link layer may ask that the data be retransmitted. task 3 If the data has no errors, the data-link layer reads and interprets the control information in the data-link header. task 4 The data-link layer strips the data of its header and trailer, and then passes the remaining data up to the network layer based on the control information in the data-link header. It is necessary to have peer-to-peer communication for the encapsulation process so that packets can travel from the source to the destination. During the encapsulation process, the protocols at each layer exchange information, called protocol data units (PDUs), between the peer layers.
- 33. Study Notes http://SlideShare.net/OxfordCambridge 33| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n At the transport layer, this information is exchanged in units known as segments. At the network layer, the information is exchanged as packets. At the data-link layer, the information is exchanged as frames. Finally, at the physical layer, the information is exchanged as bits. When discussing data at different layers, this makes it easier for people to understand which layer is being referred to, instead of simply calling all data units packets. Data packets always originate at a source and then travel to a destination point on a network. Each layer is dependent on the service provided by the OSI layer below it. The lower layer carries out the
- 34. Study Notes http://SlideShare.net/OxfordCambridge 34| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n encapsulation process to take the PDU from the upper layer into its data field. It then adds the necessary headers to the layer to perform its function. Remember that data packets can only travel on a network if each layer of the OSI model at the source communicates with its peer layer at the destination. This form of communication is known as peer-to- peer communication. 4. The TCP/IP stack As well as the universally recognized OSI reference model, there is another open standard traditionally applied to the Internet – the Transmission Control Protocol/Internet Protocol (TCP/IP) stack. Both the TCP/IP stack and the OSI model use layering. TCP/IP comprises the following four layers: application transport Internet network access Although some of the layers in the TCP/IP stack are the same as those in the OSI reference model, they do not function in the same manner.
- 35. Study Notes http://SlideShare.net/OxfordCambridge 35| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n The following are the functions of the four layers of the TCP/IP stack. application transport internet network access
- 36. Study Notes http://SlideShare.net/OxfordCambridge 36| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n application The main function of the application layer is to manage high-level protocols. This includes aspects relating to dialog control, encoding, and representation. The TCP/IP stack groups all application aspects into one layer and ensures that application-related data is properly packaged for the layer below. transport The main function of the transport layer is to handle such quality-of-service issues as reliability, flow control, and any error correction. The TCP protocol, which is part of the TCP/IP suite of protocols, provides reliable network communication. internet The main function of the Internet layer is to provide packet delivery and hierarchical addressing services. It sends source packets from any network on the internetwork and ensures they arrive at the correct destination, no matter what path they have taken to get there. network access The network access layer is also known as the host-to-network layer. It looks after all the issues handled by the OSI physical and data-link layers. This layer includes the LAN and WAN protocols. The TCP/IP stack and the OSI model share some similarities. The main similarities between the two models are: application layers packet-switched technology transport and network layers application layers Although both models have application layers, the functions of these layers in each model are slightly different.
- 37. Study Notes http://SlideShare.net/OxfordCambridge 37| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n packet-switched technology Both models operate on the premise that packet-switched, rather than circuit-switched technology, is in use. transport and network layers The functions of the transport and network layers are comparable in each model. Quizxiii Identify the similarities between the OSI reference model and the TCP/IP stack.
- 38. Study Notes http://SlideShare.net/OxfordCambridge 38| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Options: 1. Both models have an application layer 2. The Internet layer is common to both models 3. They both deal with packet-switched technology 4. They have similar transport and network layer functions There are also a number of differences between the TCP/IP stack and the OSI reference model: the OSI data-link and physical layers are combined into the network access layer in the TCP/IP TCP/IP also combines the OSI presentation and session layers into its application layer the TCP/IP stack is the standard around which the Internet developed, while the OSI model is generally only used as a guide Quizxiv In the TCP/IP stack, which layer deals with reliability, flow control, and error correction? Options: 1. Application 2. Internet 3. Network Access 4. Transport
- 39. Study Notes http://SlideShare.net/OxfordCambridge 39| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Summary The Open System Interconnection (OSI) reference model was developed by the International Organization for Standardization (ISO) to correct the problem of incompatible network communications. It is a reference model that describes how information is exchanged between points on a network. The OSI model is divided into seven layers - these are the application, presentation, session, transport, network, data-link, and physical layers. Some of the advantages of layering network functions include accelerating evolution, reducing complexity, and standardizing network component interfaces. Encapsulation refers to the process of packaging information before it is transmitted. Encapsulation occurs in descending order from the application layer through to the physical layer. Headers and trailers are placed around the data as it passes through each layer. Data packets always travel from source to destination on a network. They can only travel on a network if each layer of the OSI model at the source communicates with its peer layer at the destination. This form of communication is known as peer-to-peer communication. Another open standard traditionally applied to the Internet is the Transmission Control Protocol/Internet Protocol (TCP/IP) stack. Like the OSI model, it uses layering and is comprised of the application, transport, Internet, and network access layers. The TCP/IP and OSI models are similar in a number of ways. Both models have application, network, and transport layers, and they both deal with packet-switched technology.
- 40. Study Notes http://SlideShare.net/OxfordCambridge 40| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n D. Understanding basic networking concepts After completing this section, you should be able to distinguish between common network categorizations and identify the characteristics of data encapsulation. Exercise overview Task 1: Identifying networks Task 2: Identifying characteristics of data encapsulation Exercise overview In this exercise, you're required to distinguish between common network categorizations and identify characteristics of data encapsulation. This involves the following tasks: identifying networks identifying characteristics of data encapsulation Task 1: Identifying networks There are different categorizations of networks used to identify their size, structure, and purpose.
- 41. Study Notes http://SlideShare.net/OxfordCambridge 41| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Step 1 of 3 This network type covers a large geographic area and can be used to link together the worldwide locations of a corporation. Identify which network fits this description. Options: 1. LAN 2. MAN 3. WAN Result A WAN is a network that covers a large geographic area and can be used to link together the worldwide locations of a corporation. Option 1 is incorrect. The structure of a LAN is usually identified by a simple network structure, comprising an easily manageable number of devices. Option 2 is incorrect. A MAN could incorporate multiple office locations for a large company. Option 3 is correct. A WAN can span continents. The Internet is the best known example of a large-scale WAN. Step 2 of 3 This network type covers a large city or suburban area and consists of several LANs connected together. Identify which network fits this description. Options: 1. LAN 2. MAN 3. WAN Result A MAN covers a large city or suburban area and consists of several LANs connected together. Option 1 is incorrect. A LAN is usually the easiest type of network to access regarding the number of devices it contains. Option 2 is correct. A MAN will connect businesses and homes together in a city or suburban area. Option 3 is incorrect. A WAN extends across larger geographic areas than those covered by MANs.
- 42. Study Notes http://SlideShare.net/OxfordCambridge 42| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Step 3 of 3 This network is a high-speed, low error data network that is confined to a small area, usually within a building. Identify which network fits this description. Options: 1. LAN 2. MAN 3. WAN Result A LAN is a high-speed, low error data network that is confined to a small area, usually within a building. Option 1 is correct. A LAN is typically set up within a company to connect several computers, a server, and peripheral devices so that resources can be shared. Option 2 is incorrect. A MAN is an extension of a LAN. MANs connect many buildings together in a city or large suburban area. Option 3 is incorrect. A WAN operates on a national or international scale, connecting locations over great distances. You are now familiar with different types of networks. Task 2: Identifying characteristics of data encapsulation Data encapsulation occurs when data is systematically and consistently packaged before it is sent over the network.
- 43. Study Notes http://SlideShare.net/OxfordCambridge 43| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Step 1 of 3 Match each OSI layer to its corresponding header in the encapsulation process. Options: 1. Session 2. Presentation 3. Application Targets: A. L7 B. L6 L7 C. L5 L6 L7 Result In the encapsulation process, the application layer contains the L7 header, the presentation layer contains the L6 L7 headers, and the session layer contains the L5 L6 L7 headers. The session layer contains the L5 L6 L7 headers. At the session layer the L5 header is added to the data and this becomes the data that is passed down to the transport layer. The presentation layer contains the L6 L7 headers. The L7 header is added to the data at the application layer, and at the presentation layer the L6 header is also added. The application layer contains the L7 header, it adds this header to the user data and passes the data and header down to the next layer.
- 44. Study Notes http://SlideShare.net/OxfordCambridge 44| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Step 2 of 3 Match the packet headers with the correct OSI layers. Options: 1. L4 L5 L6 L7 2. L3 L4 L5 L6 L7 3. L2 L3 L4 L5 L6 L7 Targets: A. Data-link B. Network C. Transport Result A data packet contains the L4 L5 L6 L7 header at the transport layer, the L3 L4 L5 L6 L7 header at the network layer, and the L2 L3 L4 L5 L6 L7 header at the data-link layer. The transport layer receives the data from the session layer and adds the L4 header. The network layer adds the L3 header. This now becomes the data that is passed down to the data-link layer. The data-link layer adds the L2 header. This is the last header added to the data before it is passed to the physical layer and the bits transmitted onto the network media. Step 3 of 3 Match the encapsulation terms with the correct OSI layer. Options: 1. Bits 2. Frames 3. Packets 4. Segments Targets: A. Data-link B. Network C. Physical D. Transport
- 45. Study Notes http://SlideShare.net/OxfordCambridge 45| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Result Bits are associated with the physical layer, frames with the data-link layer, packets with the network layer, and segments with the transport layer. The physical layer receives the bits and sends them to the data-link layer for de-encapsulation. The data-link layer checks the data for any errors and if none are found, it encapsulates the data as a frame and passes it up to the network layer. The network layer exchanges the information as packets and defines the logical addressing of hosts in the network. The transport layer ensures that segments are delivered without errors to the receiving device. You are now familiar with the characteristics of data encapsulation.
- 46. Study Notes http://SlideShare.net/OxfordCambridge 46| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n II. Networking devices and topologies: E. Components of a network PC F. Network devices G. Network topologies H. Identifying network devices and topologies After completing this section, you should be familiar with: potential future developments in wireless services. identifying the characteristics and benefits of the principal and enabling technologies of 4G.
- 47. Study Notes http://SlideShare.net/OxfordCambridge 47| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n E. Components of a network PC After completing this section, you should be able to identify the major components of a network PC and list the resources required to install a NIC. 1. PC components 2. Network interface cards 1. PC components The components used by a computer to enable network connectivity include the: central processing unit (CPU) bus drives memory components ports cards These are all located in the system unit, in the case of a desktop PC.
- 48. Study Notes http://SlideShare.net/OxfordCambridge 48| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Some networking devices such as routers, hubs, and bridges have similar components to computers. A computer is composed of a number of key components. Drives CPU Expansion slots Bus Backplane components Motherboard
- 49. Study Notes http://SlideShare.net/OxfordCambridge 49| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Drives The drives on a computer include the CD-ROM DVD-ROM floppy disk hard disk The CD-ROM drive reads information from a CD-ROM disk. Modern CD-ROM drives can both read from, and write to, CD disks. A DVD-ROM drive reads information from DVD disks. DVD-ROM drives are also available that can both read from, and write to, DVD disks.
- 50. Study Notes http://SlideShare.net/OxfordCambridge 50| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n You can use the floppy disk drive to read and write to floppy disks. The hard disk drive is the computer's internal device for reading and writing data also. CPU The CPU (central processing unit) processes, manipulates, and interprets computer data sent to it from software or the user, and performs the requested operations of the hardware devices connected within the computer. The microprocessor is a silicon chip within a CPU. Expansion slots Expansion slots in a computer are used for adding cards that provide additional functionality to the computer. Some examples are Firewire cards, modem cards, and sound cards, but there are many other types of cards available also. Bus A bus is an electrical connection used to pass data and control information between different components within a computer. It also connects all the internal components of the computer to the CPU. The memory bus and Peripheral Component Interconnect (PCI) bus are typical examples of the types of buses found in a computer.
- 51. Study Notes http://SlideShare.net/OxfordCambridge 51| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Backplane components You can plug external devices, such as your mouse, keyboard, and power cable, into the backplane. A number of components form the backplane. A number of components form the backplane as follows:
- 52. Study Notes http://SlideShare.net/OxfordCambridge 52| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n - Interfaces allow external hardware to be connected to the computer's backplane. You insert a network card into the backplane of your computer if you want to connect it to a computer network. - You use the parallel port to connect devices that require the simultaneous transfer of more than one bit, such as a printer. - You can add a sound card to the backplane to enable sound functions on your computer. - The Universal Serial Bus (USB) port is used for fast serial connection transmissions of one bit at a time. - You plug a video card into a computer to enable video capabilities. Motherboard The large printed circuit board (PCB), to which everything connects within your computer, is called the motherboard. This provides a single connection for, and between, all the components and devices within the computer. Random access memory (RAM) and read-only memory (ROM) are located on the motherboard.
- 53. Study Notes http://SlideShare.net/OxfordCambridge 53| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Random access memory (RAM) and read-only memory (ROM) are located on the motherboard as follows. Random access memory (RAM) is the primary memory of your computer. Data stored here can be read from, and written to, at very fast speeds. The data stored is only temporary; it is either cleared by being replaced or lost when the power is turned off. Losing the power in your computer while it is turned on can result in the loss of data stored in RAM - unless you have saved it. Read-only memory (ROM) is non-volatile, which means it stays there even if you lose power. In general, you can read from this type of memory, but you cannot write to it. To write to it, you need special types of ROM memory that provide specific functions to the computer. Quizxv Match the PC components to their descriptions. Options: 1. Backplane 2. Bus 3. CPU 4. Expansion slot 5. CD-ROM drive Targets: A. It allows additional cards to be plugged into the motherboard B. It allows external devices to be connected C. It connects all the internal computer components to the CPU D. It is where most of the calculations take place E. It can read and write to compact discs
- 54. Study Notes http://SlideShare.net/OxfordCambridge 54| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n 2. Network interface cards A network interface card (NIC) allows a computer to communicate with other computers over a network. The NIC provides a port for the computer to physically connect to a network using a cable. A NIC is also known as a LAN adapter. It uses a serial connection to communicate with the network, but communicates with the computer over a parallel connection. You need drivers to operate a NIC in your computer. You also need memory space for its functions within the operating system - for example, Windows. A NIC uses its MAC address to identify its host computer to the network it is connected to. This MAC address is a unique address assigned to this NIC only. A MAC address is 48 bits long, and is derived partly from a unique NIC vendor-assigned number, and partly from numbers the vendor assigns to its devices. As well as drivers and memory, you need an input/output (I/O) address an interrupt request line (IRQ) signal
- 55. Study Notes http://SlideShare.net/OxfordCambridge 55| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n an input/output (I/O) address The NIC needs the input/output (I/O) address to read or write data to the computer. The address identifies a part of memory that is assigned for use by the NIC. an interrupt request line (IRQ) signal An interrupt request line (IRQ) signal identifies which device in the computer is requesting the CPU to perform a function. For example, when data arrives into a NIC, its IRQ indicates to the CPU that it has data that needs to be processed for the NIC. Your choice of NIC depends on your cable expansion slots network
- 56. Study Notes http://SlideShare.net/OxfordCambridge 56| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n cable Different NICs use different port connector types. This depends on the type of network implemented and the cable being used - for example, Ethernet RJ-45 connectors on twisted pair cable. expansion slots Peripheral Component Interconnect (PCI) expansion slots are standard, but older computers may have Industry Standard Architecture (ISA) slots. network If you are connecting to a Token Ring LAN, you should use a Token Ring NIC, for example. To install a NIC, you need to understand the configuration and operation of: erasable programmable read-only memory (EPROM) jumpers and switch settings plug-and-play software If there is a problem with the NIC, you should be familiar with the network card diagnostics – such as loopback tests and the diagnostics procedure supplied by the NIC vendor. You should also be able to fix hardware resource conflicts with IRQs and direct memory access (DMA). DMA enables RAM to communicate with a device directly without using the CPU.
- 57. Study Notes http://SlideShare.net/OxfordCambridge 57| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Some NICs have specialized functions in networks and require specific technical expertise. Quizxvi What should you know before installing a NIC? Options: 1. How the network card is configured 2. How to configure specialized functions in different types of network cards 3. How to fix hardware resource conflicts 4. How to use the network card diagnostics Quizxvii What factors should you consider before installing a NIC? Options: 1. Cable type 2. Network type 3. Type of CPU 4. Type of expansion slot
- 58. Study Notes http://SlideShare.net/OxfordCambridge 58| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Summary To enable network connectivity, a computer uses components such as the central processing unit (CPU), bus, drives, cards, ports, and memory. A computer is composed of drives, the CPU, expansion slots, a bus, a motherboard, and a backplane. A network interface card (NIC) is a device that enables a computer to communicate with a network. Selecting a NIC depends on the type of network, cable, and expansion slot on your computer. If installing a NIC, you should be able to configure it, perform its diagnostics, and resolve hardware conflicts.
- 59. Study Notes http://SlideShare.net/OxfordCambridge 59| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n F. Network devices After completing this section, you should be able to identify the functions, features, and operation of network devices used at different layers of the OSI model. 1. OSI layer 1 devices 2. OSI layer 2 devices 3. OSI layer 3 devices 4. Multiple layer devices The Open System Interconnection (OSI) model is used as a reference model to relate network components to their functions. Components used in layers 1 to 3 include devices such as:
- 60. Study Notes http://SlideShare.net/OxfordCambridge 60| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n routers, switches and firewalls hubs and bridges repeaters network interface cards AAA services 1. OSI layer 1 devices There are a number of commonly used layer 1 (physical layer) devices. These include: repeaters hubs repeaters In layer 1 of the OSI model, repeaters regenerate and retransmit the electrical network signals, so that they can travel greater distances without deteriorating. They are used to increase the area a network can cover by extending the reach of the network cables used. Repeaters are considered layer 1 devices because they operate at bit level. A multiport repeater is called a hub. hubs Like repeaters, some hub types can regenerate and retransmit network signals, but while a repeater has only two ports, a hub can have several – up to 20 – ports. A hub receives on one port and retransmits the signal to all other ports.
- 61. Study Notes http://SlideShare.net/OxfordCambridge 61| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n There are hubs that can amplify and propagate signals, and are used as network concentration points. Hubs do not perform filtering, nor do they perform path determination. They are commonly used in Ethernet 10BaseT or 100BaseT networks. Hubs increase the reliability of a network because the failure of one cable connection to the central hub will not result in network failure, as only that port is affected. Quizxviii Identify the functions of a hub. Options: 1. Forwards network signals at bit level 2. Receives data on several ports and transmits on one port 3. Creates a central connection point for network cables 4. Performs path determination and switching 2. OSI layer 2 devices Layer 2 (data-link layer) devices facilitate the transmission of data. There are a number of devices that operate at this layer. Network Interface cards (NICs) Bridges Switches
- 62. Study Notes http://SlideShare.net/OxfordCambridge 62| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Network Interface cards (NICs) Network Interface Cards (NICs) are defined as layer 2 devices because each one has a unique Media Access Control (MAC) address identifying the host on the network. NICs are used to control data communications. Bridges Bridges are layer 2 devices that create local area network (LAN) segments. A bridge provides extra bandwidth needed for data exchange by: filtering local LAN traffic, maintaining connectivity between network segments directly connected to it. Bridges are preferable over hubs because they can efficiently manage data transmission between connected segments based on the MAC addresses, and filter out unnecessary traffic from reaching a segment.
- 63. Study Notes http://SlideShare.net/OxfordCambridge 63| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n By transmitting data only to the required network segment based on the MAC addresses used, bridges are able to forward data quickly and efficiently without clogging up network segments. One of the functions of a bridge is to ensure that data is delivered only to the required segments of the network. This means that there is more bandwidth available on the individual segments as they are not receiving data from every segment. Bridges gather and manage MAC addresses in tables. On a bridge, each port creates a separate collision domain, so a collision on one segment does not affect other segments. This means several devices can communicate simultaneously in a LAN without affecting each other. Bridges use their MAC address tables to gauge whether the destination of a packet is on the same segment or a different segment to that of the sender. It then sends the data to the destination segment only. This has the effect of reducing network traffic, as data is not needlessly sent throughout the LAN. Description of how a bridge operates on a network follows. Two small network segments containing approximately four computers each are connected by a bridge. The bridge only allows data from one segment to cross the bridge to the other segment if it is using a destination address from there.
- 64. Study Notes http://SlideShare.net/OxfordCambridge 64| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Switches Switches are hardware devices used at layer 2, which create multiple bridge connections. Switches are often used instead of hubs, and can reduce the disruption caused by data traffic on a network. Switches connect LAN segments into single networks, and use MAC addresses to decide where to forward traffic. They are faster than bridges, because the switching decisions are performed using specialized hardware instead of software. A switch port connected to a host behaves like a separate bridge and provides the host with the full bandwidth of the cable. This is often called micro segmentation. Description of how switches forward traffic follows. A switch uses the MAC address of a data packet sender to identify it. It locates the packet's destination based on the destination's MAC address.
- 65. Study Notes http://SlideShare.net/OxfordCambridge 65| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Quizxix What are the advantages of using a bridge? Options: 1. It allows more than one device to transmit simultaneously 2. It can rapidly forward data 3. It does not process all received data 4. It keeps track of which MAC addresses are on each side of the bridge 3. OSI layer 3 devices In network communications, two types of addressing are used: layer 2 layer 3 layer 2 The layer 2 addressing scheme uses the MAC address (physical address) to identify network hosts.
- 66. Study Notes http://SlideShare.net/OxfordCambridge 66| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n layer 3 The layer 3 addressing scheme uses a logical address, such as an IP address, to identify network hosts. The purpose of a router is to use layer 3 (network layer) addresses to transmit data packets between networks. It uses IP addresses instead of MAC addresses to decide on the optimum path to be used for data delivery.
- 67. Study Notes http://SlideShare.net/OxfordCambridge 67| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Routers have become important to the maintenance of the Internet because of their ability to transmit packets based on layer 3 information. They can also be used to connect different layer 2 technologies - for example, Token Ring and Ethernet - which enables virtually any kind of computer to communicate with any other computer anywhere on the globe.
- 68. Study Notes http://SlideShare.net/OxfordCambridge 68| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Routers can also examine layer 4 information when sending data between devices or networks. Multilayer switches are similar to layer 2 switches except that they use layer 3 network addresses (IP) as well as using layer 2 MAC addresses.
- 69. Study Notes http://SlideShare.net/OxfordCambridge 69| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Using software processes to carry out layer 3 routing can frequently cause bottlenecks, but layer 3 routing functions can now be carried out in the switch hardware. High-speed hardware-based multilayer switches can now deliver layer 3 functions with the same speed as layer 2 functions. Using hardware to enable layer 3 routing functions provides an improved quality of service. Hardware- based layer 3 routing functions use the location of the sender and receiver in each transmission to prioritize the packets being delivered.
- 70. Study Notes http://SlideShare.net/OxfordCambridge 70| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n This allows hardware-based functions to prevent traffic from unnecessarily entering networks for which it is not intended. Quizxx How does a router establish the destination network for data? Options: 1. It examines the destination IP address 2. It examines the destination MAC address only 3. It examines the destination MAC and IP addresses 4. Multiple layer devices A gateway is a complex network device that connects disparate network environments - for example, a LAN environment to a mainframe environment. A gateway uses a combination of hardware and software, and can carry out translations at various layers of the OSI model.
- 71. Study Notes http://SlideShare.net/OxfordCambridge 71| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n E-mail programs typically use gateways to communicate with Internet mail servers. They use gateways to translate LAN-based mail messages into Simple Mail Transfer Protocol (SMTP) format. There are other network devices that work at and above the lower three layers. These include: firewalls AAA servers
- 72. Study Notes http://SlideShare.net/OxfordCambridge 72| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n firewalls Firewalls are positioned on the edge of private networks, and protect them from any unwanted traffic or attacks attempting to access the internal network. A firewall examines all traffic and packets to ensure that they are legitimate, dropping any that fail to conform to its rules of entry. When there is more than one internal network, a firewall can control access to them from the outside, and traffic between the internal networks also. AAA servers An authentication, authorization, and accounting (AAA) server processes requests from users to gain access to network resources. The AAA server: only allows authenticated users onto the network gives users access only to the resources they are authorized to use keeps an account of user behavior
- 73. Study Notes http://SlideShare.net/OxfordCambridge 73| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Quizxxi Which sentence best describes the function of a gateway? Options: 1. A device used by e-mail programs to determine routing paths for IP traffic 2. A combined hardware/software device that connects dissimilar network environments 3. A translation device that operates solely at layer 1 of the OSI model Quizxxii Match each network device with a description of its function. Options: 1. Bridge 2. Repeater 3. Router Targets: A. Creates separate collision domains on each port B. Employs layer 3 addresses to transmit data packets between networks C. Regenerates and retransmits network signals at layer 1 of the OSI model Summary Hubs, switches, and routers are all networking devices used to connect networks. Networking devices operate chiefly at the lower three layers of the Open System Interconnection (OSI) model. Layer 1 devices, such as repeaters and hubs, are used to propagate network signals at bit level. Network Interface Cards (NICs), bridges, and switches are OSI layer 2 devices used to transmit data. Every NIC has a unique Media Access Control (MAC) address that is used to identify its host to switches and bridges. These devices forward traffic based on the host's MAC address. Routers use layer 3 addresses to transmit packets between networks. Multilayer switches use layer 3 network addresses (IP) as well as layer 2 MAC addresses to manage packet traffic. Hardware-based layer 3 routing functions provide faster operation than software versions. Gateways are used to connect disparate network environments. Firewalls and AAA (authentication, authorization, and accounting) servers protect networks from unauthorized attacks and unauthorized access.
- 74. Study Notes http://SlideShare.net/OxfordCambridge 74| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n G. Network topologies After completing this section, you should be able to distinguish between the features of different network topologies. 1. Distinguishing physical and logical topologies 2. Identifying topology types 1. Distinguishing physical and logical topologies Networks can have different topologies. A network topology describes how the network is laid out, and how data is transmitted on it. A network has two topologies: logical topology physical topology logical topology The logical topology describes the structure and the path connection types between the different parts of the network. It defines how data flows in the network.
- 75. Study Notes http://SlideShare.net/OxfordCambridge 75| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n physical topology The physical topology describes the physical arrangement of the devices and cables on a network. It shows the actual paths taken by data when traveling around the network. A network can have the same logical and physical topologies, but this is not always the case. A network with a logical bus topology, for example, can also have a physical bus topology structure.
- 76. Study Notes http://SlideShare.net/OxfordCambridge 76| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n The physical layout of a network does not necessarily determine how data flows in it. For example, a Token Ring network can have a physical star topology, but use a logical ring topology to communicate data. A Token Ring network can use a logical ring topology with either a physical ring or physical star topology. Ethernet can use either of these two physical topologies with a logical bus topology. Quizxxiii Identify the correct statements about network topologies. Options: 1. A logical topology defines precisely the arrangement of devices on the network 2. A physical topology describes the paths that signals use to travel from one point on the network to another 3. Networks can have a physical and a logical topology 4. The physical topology defines the way in which network devices are connected together
- 77. Study Notes http://SlideShare.net/OxfordCambridge 77| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n 2. Identifying topology types Different network topologies are used as template structures to define how best to implement networks. The topology outlines the way in which the computers, printers, and other network devices are linked together. Bus Star Ring Mesh Bus A bus topology functions like a single path with all devices connecting to it. In this topology, all the computers are connected by a single cable, and all data communications pass through this cable in a linear fashion. At the end of the main cable, a terminator device is used to absorb the signal when it arrives at the end of the cable. Without the terminator, the signal can bounce back and cause problems on the network. This type of problem is called signal reflection. A bus topology is also known as a linear bus.
- 78. Study Notes http://SlideShare.net/OxfordCambridge 78| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Description of how a bus topology works follows. Six computers are connected in a bus topology by a central cable. A packet moving on the cable communicates with each device as it passes, before terminating at the terminator device at the end of the cable. Star Ethernet LANs typically use a star topology. This comprises a central connection device, such as a switch, with each computer on the network connected to this device by its own cable. Star topologies are relatively expensive to implement, but they have many advantages. The chief advantage of this topology is that each host is connected to the central device by its own cable. Any problems that occur between one host and the central device are contained on that cable section, and can be easily located. This means that the rest of the network is not affected. Another advantage is that the cables used to each host from the central device can be the maximum allowed. Hosts can be located anywhere within the maximum cable radius of the central device. In a bus topology, on the other hand, place of hosts is limited because they must be close to the main bus cable. An extended star topology exists when you connect one or more networking devices to the main networking device in a star topology. In this way, the star topology is extended.
- 79. Study Notes http://SlideShare.net/OxfordCambridge 79| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Ring On a ring topology, network hosts are arranged and connected in a logical circle. This removes the requirement for a terminator device. Data is transmitted around the ring by a token that stops at each network host. If the host wants to send data, it adds it to the token along with the destination address of the data. As the token continues around the ring, it reaches the destination host, which takes the data out of the token. Only one device can transmit at any time as the device must have control of the token to do so. The main advantage is that there are no packet collisions in a ring topology system. Two types of ring topology include: - Single - Dual Single : all devices in a single ring topology share a single cable, and must wait their turn to send data on it. Data on this topology travels in one direction only. Dual-ring topologies use two rings to allow data to flow in both directions. They also incorporate fault tolerance, which means that if one ring fails, the other ring is used to transmit data. A Fiber Distributed Data Interface (FDDI) typically uses a dual-ring topology. Mesh
- 80. Study Notes http://SlideShare.net/OxfordCambridge 80| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n A mesh topology enables each network host to have a direct connection with each of the other network hosts. There are two types of mesh topology: On a full mesh topology, each network host is directly connected to all the other network hosts. This provides a high level of fault tolerance and redundancy within the network. This kind of topology is complex and expensive to implement. As the name suggests, in a partial mesh topology at least one network host is directly connected to a number of other hosts. The remaining hosts might be connected to some but not all of the other hosts.
- 81. Study Notes http://SlideShare.net/OxfordCambridge 81| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Quizxxiv On a star topology, what happens when the cable between a network host and the central device fails? Options: 1. Nothing, because all the devices remain online 2. Only the host at the end of the cable is disconnected 3. The network resets itself 4. The whole network becomes disconnected Quizxxv Match each topology to its description. Options: 1. Bus 2. Ring 3. Star Targets: A. Each host is connected to the central connection device by its own cable B. Hosts attach data and a destination address to the passing token C. Requires a terminator device to function properly Summary A network topology describes how the network is laid out, and how data is transmitted on it. The physical topology defines the physical arrangement of the devices and cables on a network. The logical topology defines the paths used by information to flow through a network. A network can have the same logical and physical topologies, but this is not always the case. Typical network topology types commonly used include the bus, star, extended star, ring, full mesh, and partial mesh topologies.
- 82. Study Notes http://SlideShare.net/OxfordCambridge 82| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n H. Identifying network devices and topologies After completing this topic, you should be able to match network devices to their functions and distinguish between different network topologies. Exercise overview Task 1: Identifying network device functions Task 2: Selecting network topologies Exercise overview In this exercise, you're required to identify the functions of network devices, and to select appropriate topologies for given scenarios. This involves the following tasks: identifying network device functions selecting network topologies Suppose your company is moving to a server-based model and has purchased new network devices for its upgrade. Task 1: Identifying network device functions Commonly used network devices include repeaters, hubs, NICs, switches, and routers.
- 83. Study Notes http://SlideShare.net/OxfordCambridge 83| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Step 1 of 3 Identify the correct statements about hubs and repeaters. Options: 1. A repeater is a networking device that exists at layer 3 2. Hubs are used as network concentration points 3. Hubs perform filtering 4. A repeater regenerates signals so that they can cover greater distances along a cable Result Hubs are used as network concentration points, and a repeater regenerates signals so that they can cover greater distances along a cable. Option 1 is incorrect. Because they operate only at the bit level and look at no other information, repeaters are classified as layer 1 devices. Option 2 is correct. A hub provides extra reliability to the network by acting as a central connection point, thereby ensuring that the failure of one cable will not disrupt the entire network. Option 3 is incorrect. Filtering is not provided at layer 1 of the Open System Interconnection (OSI) model. Layer 2 devices, such as switches, provide filtering. Option 4 is correct. The longer the cable length, the more the signals deteriorate. As a result, a repeater works to regenerate these signals and ensure that they are clean and easily recognizable.
- 84. Study Notes http://SlideShare.net/OxfordCambridge 84| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Step 2 of 3 Match each layer 2 device to its description. Options: 1. Bridge 2. Network interface card (NIC) 3. Switch Targets: A. Carries a unique hardware address used to control data communication B. Creates two or more LAN segments C. Used for multiple bridge connections Result A bridge is designed to create two or more LAN segments, a NIC is a network device that carries a unique hardware address used to control data communication, and a switch is used for multiple bridge connections. A bridge creates two or more LAN segments, with each segment being a separate collision domain. The unique hardware address that a NIC carries is called a Medium Access Control (MAC) address. A bridge makes forwarding decisions based on these MAC addresses. Switching is performed in hardware instead of software, making it significantly faster. Step 3 of 3 Which statements about layer 3 devices are correct? Options: 1. A multilayer switch can examine layer 4 information 2. A multilayer switch is a network device used for switching, using layer 3 MAC addresses 3. A router is an internetworking device that forwards data packets between networks 4. A router matches information in its routing table with the destination IP address of the data Result A multilayer switch can examine layer 4 information. A router is an internetworking device that matches information in the routing table with the destination IP address of the data and forwards data packets between networks. Option 1 is correct. A multilayer switch can examine layer 4 information, such as Transmission Control Protocol (TCP) headers - for example, identifying the type of application from which a packet came.
- 85. Study Notes http://SlideShare.net/OxfordCambridge 85| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Option 2 is incorrect. A MAC address is a layer 2 address. A multilayer switch is also used for switching, using layer 3 network addresses (IP addresses). Option 3 is correct. A router forwards data packets between networks based on layer 3 addresses. Option 4 is correct. A router uses the destination IP address to find which destination network in its routing table the data is to be sent to. You are now familiar with the functions of common network devices. Task 2: Selecting network topologies Networks can have different topologies. A network topology describes how the network is laid out, and how data is transmitted on it. Step 1 of 3 Match each topology description to a topology type. Options: 1. All the cabling segments meet at a central connection point in this topology 2. All the devices on this topology are directly connected to each other 3. There is no beginning or end to this topology and data travels in one direction only 4. This topology requires a terminator device to avoid signal interference Targets: A. Full mesh
- 86. Study Notes http://SlideShare.net/OxfordCambridge 86| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n B. Ring C. Star D. Bus Result In a full mesh topology, all the devices are directly connected to each other. A ring topology has no beginning or end and data travels in one direction only. A star topology is made up of a central connection point, where all the cabling segments meet. A bus topology requires a terminator device to avoid signal interference. In a star topology, cable difficulties affecting one host are confined to that segment, so the rest of the network remains operational. Full mesh means that all nodes in the network have a direct connection to each other. A full mesh topology is difficult and expensive to implement. Because of the structure of the ring topology, there is no need to use terminator devices to prevent signal reflection. A bus topology experiences signal interference unless it is equipped with a terminator device at each end of the bus cable. Step 2 of 3 As well as bus, star, ring, and full mesh topologies, other topologies include dual ring, extended star, and partial mesh topologies. Match each topology type with its description. Options: 1. Dual ring 2. Extended star 3. Partial mesh Targets: A. Each connection to a central device can be expanded by including an additional networking device in this topology B. In this network, some devices maintain multiple direct connections to all others, but not all devices are directly connected to each other C. This is a network that allows data to be sent in both directions and provides redundancy Result In an extended star topology network, connections to a central device can be expanded by including an additional networking device. A dual ring topology network provides redundancy, and allows data to be sent
- 87. Study Notes http://SlideShare.net/OxfordCambridge 87| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n in both directions. In a partial mesh topology network, some devices maintain multiple direct connections to all others, but not all devices are directly connected to each other. A dual ring topology allows data to be sent in both directions, so if one ring fails, data can be transmitted on the other ring. An extended star topology is characterized by a star network with additional devices placed on each segment to expand the network structure. Unlike a full mesh topology, not all devices are connected to each other in a partial mesh network. Step 3 of 3 Suppose your company's Ethernet LAN has a combination of hosts and important servers sharing the same physical location. Keeping the servers accessible to hosts on the network is critical. You want to implement a topology that, in the event of a cable failure, will enable the rest of your network to maintain normal functionality. Which physical network topology should you deploy? Options: 1. Bus 2. Ring 3. Star Result To enable the rest of your network to maintain normal functionality in the event of a cable failure, you should deploy a star network topology rather than a bus or ring topology. Option 1 is incorrect. On a bus network topology, devices share the same cable. A problem on one section of this network can, therefore, affect other sections. Option 2 is incorrect. If a cable fails in a ring network topology, the ring is broken and a token cannot pass from one device to the next in the ring. Option 3 is correct. On a star topology, each device has an independent connection to the central connection device, so that in the event of one segment having problems, the rest of the network is not affected. You are now familiar with the characteristics of physical topologies.
- 88. Study Notes http://SlideShare.net/OxfordCambridge 88| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n
- 89. Study Notes http://SlideShare.net/OxfordCambridge 89| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n III. Physical media: I. Network cabling and wireless media J. Network cable connectors K. Network installation tools L. Connecting the network After completing this section, you should be familiar with: potential future developments in wireless services. identifying the characteristics and benefits of the principal and enabling technologies of 4G.
- 90. Study Notes http://SlideShare.net/OxfordCambridge 90| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n I. Network cabling and wireless media After completing this section, you should be able to differentiate between types of network media. 1. Unshielded and shielded twisted pair cable 2. Coaxial cable 3. Fiber optic cable 4. Wireless communications 1. Unshielded and shielded twisted pair cable In network communications, a medium is the physical means by which two devices communicate, such as a cable. The most common cable types include: twisted pair coaxial fiber optic The use of wireless communication media has also grown rapidly over the past years. Twisted pair cables can be shielded or unshielded. An Unshielded Twisted Pair (UTP) cable consists of four twisted copper wire pairs. Wires in a pair are twisted around each other, and each wire in a UTP cable is insulated.
- 91. Study Notes http://SlideShare.net/OxfordCambridge 91| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n There are two advantages of using UTP cable: small diameter reduced interference small diameter UTP cable has a comparatively small diameter – approximately 0.43 cm (which is about 0.17 inches) – and this makes it easier to work with. reduced interference There is less interference with UTP cable. Using twisted pair cables reduces electromagnetic and radio frequency interference. The number of twists per meter on a cable is determined by precise specifications. However, you can reduce signal interference by varying the number of twists in a wire pair. UTP cable is popular, because it can be used with most networking architectures. UTP cable, when used as a networking medium, has four pairs of 22 or 24 gauge copper wire. Unlike telephone cable, UTP has an impedance rate of 100 ohms. UTP cable is available in the following categories. Category 1
- 92. Study Notes http://SlideShare.net/OxfordCambridge 92| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Category 2 Category 3 Category 4 Category 5 Category 5e Category 6 Category 1 Category 1 cable transfers telephone communications at a speed of 56 Kbps, and is not suitable for data transmission. Category 2 Category 2 cable was created for use with Token Ring networks over UTP. It transmits data at speeds of up to 4 Mbps. Category 3 Category 3 cable can be used on 10BaseT networks, Ethernet networks, and 4Mbps Token Ring networks. It transmits data at speeds of up to 10 Mbps. Category 4 Although category 4 cable is no longer popular, it is used in high-speed Token Ring networks to transmit data at speeds of up to 16 Mbps. Category 5 Category 5 cable is commonly used for cabling desktops, and can transmit data at speeds of up to 100 Mbps. Category 5e Category 5e cable is best suited for use on Gigabit Ethernet networks, or networks running at 1 Gbps. It is comparatively expensive. Category 6
- 93. Study Notes http://SlideShare.net/OxfordCambridge 93| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Category 6 cable can transmit data at speeds of up to 1000 Mbps. Like category 5e cable, it can also run at multigigabit speeds given the appropriate specifications. Generally, it transmits data at up to 1000 Mbps. It is composed of four pairs of 24 gauge copper wires. Quizxxvi Match each UTP category to its maximum data transmission speed. Options: 1. Category 3 2. Category 5 3. Category 5e Targets: A. 1 Gbps B. 10 Mbps C. 100 Mbps In a Shielded Twisted Pair (STP) cable, eight wires are wrapped in pairs and each pair is wrapped in a metallic foil. The combination of twisting the cable and the shielding reduces signal degradation. The four pairs are then coated with another metal foil, typically a 150 ohm cable. This structure reduces electrical noise caused by pair-to-pair coupling, crosstalk, and noise from outside the cable – such as radio frequency interference (RFI) or electromagnetic interference (EMI). STP is used on Token Ring networks and on Ethernet networks. There are a number of benefits with STP and UTP cable: inexpensive fast
- 94. Study Notes http://SlideShare.net/OxfordCambridge 94| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n adaptable inexpensive Although STP is more expensive than UTP, both are relatively inexpensive cabling standards. fast The transmission speed of both STP and UTP is suitable for local area traffic. adaptable Transmission standards are commonly modified to accommodate existing UTP cabling, because replacing such cabling would be more expensive. All Ethernet cable types are described using the following naming convention, N<Signal>X. N <Signal> X N N represents the signaling rate in megabits per second. For example, in the cable grade 100BaseX, the number 100 indicates that the cable has a transmission speed of 100 Mbps. <Signal> <Signal> represents the signaling type. This can be either base, which is short for baseband, or broad, which stands for broadband. X X indicates a unique identifier for a specific Ethernet cabling scheme. It indicates either the maximum distance the signal can travel or the cable type. For example, the number 5 in 10Base5 indicates the signal can travel 500 meters. The letter T in 10BaseT indicates that this is a twisted pair cable. 2. Coaxial cable A coaxial cable consists of a central copper conductor encased by a layer of insulation. This is covered by either a metal foil or by woven copper. This metal layer shields the central wire from interference, but also acts as a second conductor. This is then covered by an outer insulating layer.
- 95. Study Notes http://SlideShare.net/OxfordCambridge 95| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Coaxial cable can operate over greater distances than twisted pair cable, and transmits at speeds of 10 to 100 Mbps. It requires fewer boosts to maintain signal strength, because repeaters regenerate the signals in the network. Installing coaxial cable is more expensive than installing twisted pair cable. Coaxial cable has the following advantages: it is compatible with many communication types it is inexpensive to install signal strength is maintained it is compatible with many communication types Coaxial cable is commonly available, and is consequently compatible with many data communication types. it is inexpensive to install Although more expensive than UTP, coaxial cable is inexpensive compared with fiber optic cable. signal strength is maintained The strength of a signal can be maintained for longer distances between networks than either STP or UTP cable can achieve. Coaxial cable types include Thinnet (10Base2) and Thicknet (10Base5). Although rarely used today, Thicknet and Thinnet coaxial cable types were formerly very common. Thicknet and Thinnet have the following different attributes: Thicknet Thinnet
- 96. Study Notes http://SlideShare.net/OxfordCambridge 96| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Thicknet Thicknet was traditionally used as Ethernet backbone cable owing to its noise rejection and transmission length capabilities. It had the largest diameter, but was comparatively rigid, which made it more difficult to work with. Consequently, it was only used for very specific tasks. Thinnet Formerly used on Ethernet networks, Thinnet cable measured 3.5 millimeters in diameter which made it comparatively easy and cheap to install. One disadvantage of Thinnet, however, was that it needed a solid electrical connection at each end to ensure that it was grounded. The outer metal conductor on the cable took up half the circuit, and connections were prone to electrical noise and interference.
- 97. Study Notes http://SlideShare.net/OxfordCambridge 97| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Quizxxvii Identify the true statements about coaxial cable. Options: 1. Coaxial cable can run for longer distances than either STP or UTP cable 2. Thicknet coaxial cable is used for installations that require the cable to make many twists and turns 3. Thicknet was commonly used as Ethernet backbone cable 3. Fiber optic cable Fiber optic cable is used for modular light transmission. Instead of transmitting electrical signals, it transmits pulses of light that represent bits.
- 98. Study Notes http://SlideShare.net/OxfordCambridge 98| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n A significant advantage of fiber optic cable is that it supports line speeds of over 100 Gbps. It is more expensive than twisted pair or coaxial cables. The following are the light-guiding components of an optical fiber. Core fiber Cladding
- 99. Study Notes http://SlideShare.net/OxfordCambridge 99| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Core fiber The core fiber is made of pure glass, or high-grade plastic, capable of a high light-refraction index. Some fibre optic cable now uses high-grade plastics in the core. Cladding A cladding layer made of plastic or glass prevents light escaping from the core in a process called total internal reflection. This allows light to be sent through the cable around bends. To conform to certain standards, fiber optic cable is sometimes strengthened by a further layer of steel. Fiber optics are made with different sizes of fiber and cladding. Most network technologies demand that fiber optics be paired to form a duplex fiber optic cable. Fiber optic cables are available as single-mode or multimode cable: single-mode multimode
- 100. Study Notes http://SlideShare.net/OxfordCambridge 100| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n single-mode A single-mode cable uses lasers to generate light. It allows just one mode of light to pass through it at a time, but is capable of greater bandwidth and greater distances than multimode cable. It is more expensive than multimode cable, and has a maximum cable length of 60 kilometers. multimode Multimode cable allows multiple light modes to pass along its fibers. Favored in workgroup applications, multimode cable uses light emitting diodes (LEDs) to generate light. A multimode fiber optic cable cannot exceed 2 kilometers.
- 101. Study Notes http://SlideShare.net/OxfordCambridge 101| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n In 2002, the Institute of Electrical and Electronics Engineers (IEEE) passed 10 Gigabit Ethernet as the approved fiber optic cable for use on local and wide area network (WAN) backbones. High-speed Ethernet networks, such as 1000BaseX and 1000BaseT, have advanced the performance of large networks. The Ethernet industry has seen a huge increase in the number of Gigabit ports. The 10 Ethernet Gigabit standard is necessary to network these ports. On large LAN applications, 10 Gigabit Ethernet enables managers to scale their Ethernet networks - for example, from 100 Mbps to 10,000 Mbps - while also increasing their network performance. For wide area applications, 10 Gigabit Ethernet is cost-effective, and gives improved performance links. These links are also easy to manage. Cable types The commonly used cable types.
- 102. Study Notes http://SlideShare.net/OxfordCambridge 102| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Ethernet Name Cable Type Maximum Speed Maximum Transmission Distance Comments 10BaseF Fiber 10Mbps 500 to 2000 meters per segment Used for Ethernet over fiber optic networks. 100BaseFX Fiber 100Mbps 2000 meters per segment Used for 100Mbps over fiber optic networks. 1000BaseT Copper 1000Mbps 100 meters per segment 1000BaseSX (Gigabit Ethernet) Multimode Fiber 1000Mbps 260 meters per segment Uses SC fiber connectors. 1000BaseTX (Gigabit Ethernet) Category 5 UTP 1000Mbps 100 meters per segment Uses the same connections as 10BaseT. 1000BaseLX Multimode Fiber or Single-mode Fiber 1000Mbps 550 meters per segment of multimode fiber or 3,000 meters per segment of single-mode fiber. Uses longer wavelength laser than 1000BaseSX. FDDI Multimode Fiber 100Mbps 10 kilometers per segment Uses an MIC connector. Quizxxviii Identify the true statements about fiber optic cable. Options: 1. Cladding material is used to prevent light escaping from the core 2. Fibers are twisted to reduce interference 3. Fiber optic cable is used for modular light transmission 4. Multimode cable uses lasers to generate light 4. Wireless communications Wireless communications are based on electromagnetic waves that are capable of traveling through a vacuum. Unlike other networks, they are not connected by cables. Wireless networks have become more popular, although they use a different technology type.
- 103. Study Notes http://SlideShare.net/OxfordCambridge 103| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Rather than using cables, wireless networks are enabled using radio frequencies and infrared waves wireless adapter cards wireless hubs radio frequencies and infrared waves Radio frequencies and infrared waves are used to communicate data in wireless networks. wireless adapter cards A computer, typically a laptop, needs a wireless adapter card to receive data from a wireless network. wireless hubs
- 104. Study Notes http://SlideShare.net/OxfordCambridge 104| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Instead of routers, a wireless LAN uses wireless hubs called access points to access a network, or to send signals. Wireless signals are more versatile than conventional network signals because they do not require a physical medium. They can transmit data, video, and voice, using the radio frequency (RF) spectrum. They can transmit at rates of between 9 Kbps and 54 Mbps, while the wireless frequency ranges from 3 kHz to 300 GHz. Wireless technology is now widespread and there are a number of common devices and technologies available. You can use a cellular phone to access the Internet radio frequency to send and receive data over the air a wireless mouse (with infrared or RF signals) to communicate with a computer Bluetooth technology (which creates a personal-area network by wirelessly connecting devices such as phones, tablets, and PCs)
- 105. Study Notes http://SlideShare.net/OxfordCambridge 105| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Wireless LANs (WLANs) are a prominent example of wireless communications and are considered central to the already started future of communications. WLANs use radio waves to communicate signals instead of cables. They also use microwave and infrared (IR) waves. The performance of your network and its ability to cope with future requirements depend heavily on the sort of media you choose to transmit information. The table below outlines common network media features, such as maximum speeds and distances. It includes UTP, STP, coaxial, and fiber optic cable, and wireless connections.
- 106. Study Notes http://SlideShare.net/OxfordCambridge 106| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Complete list of cable types Ethernet Name Cable Type Maximum Speed Maximum Transmission Distance Notes 10Base5 Coaxial 10Mbps 500 meters per segment Also called Thicknet. 10Base2 Coaxial 10Mbps 185 meters per segment Also called Thinnet. 10BaseT UTP 10Mbps 100 meters per segment Popular networking cable scheme. 100BaseT UTP 100Mbps 100 meters per segment Popular networking cable scheme. 100BaseVG UTP 100Mbps 213 meters (Cat 5) 100 meters (Cat 3) 100BaseT4 UTP 100Mbps 100 meters per segment Requires four pairs of Cat 3, 4, or 5 UTP cable. 100BaseTX UTP, STP 100Mbps 100 meters per segment Requires two pairs of Cat 5 UTP, or Type 1 STP. 10BaseF Fiber 10Mbps 500 to 2000 meters per segment Used for Ethernet over fiber optic networks. 100BaseFX Fiber 100Mbps 2000 meters per segment Used for 100Mbps over fiber optic networks. 1000BaseT Copper 1000Mbps 100 meters per segment 1000BaseSX (Gigabit Ethernet) Multimode Fiber 1000Mbps 260 meters per segment Uses SC fiber connectors. 1000BaseTX (Gigabit Ethernet) Category 5 UTP 1000Mbps 100 meters per segment Uses the same connections as 10BaseT. 1000BaseLX Multimode Fiber 1000Mbps 550 meters per segment Uses longer wavelength laser than 1000BaseSX. FDDI Multimode Fiber 100Mbps 10 kilometers per segment Uses an MIC connector. Quizxxix Match each cable type to its description. Options: 1. Coaxial 2. Fiber optic 3. UTP
- 107. Study Notes http://SlideShare.net/OxfordCambridge 107| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Targets: A. Has a maximum transmission length of 100 meters B. Transmits pulses of light C. Was traditionally used to cable Ethernet backbones Summary Twisted pair cable is a common cable type - it is available as shielded twisted pair (STP) or unshielded twisted pair (UTP). STP cable combines the techniques of twisting wires and shielding. UTP cable is a copper wire-based cable used in a variety of networks. Coaxial cable operates over relatively large distances, and transmits data at speeds of up to 100 Mbps. Installing coaxial cable is more expensive than installing twisted pair cable. Fiber optic cable transmits bits in the form of modulated light data. Light is refracted along the cable and can go around bends. Fiber optic cables are available as single-mode or multimode cable. Wireless signals are radio frequencies and infrared waves that can travel through air. They have been a growth area in network communications.
- 108. Study Notes http://SlideShare.net/OxfordCambridge 108| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n J. Network cable connectors After completing this section, you should be able to recognize the types of cable connectors used in modern networks. 1. Twisted pair and coaxial cable connectors 2. Fiber optic cable connectors 3. The IEEE 1394 standard 1. Twisted pair and coaxial cable connectors Modern networks use different cable connectors, depending on the type of cable used. The most common types of network cabling used are coaxial, twisted pair and fiber optic. Typical types of connectors used with these are Registered Jack (RJ), DB, Bayonet Neill-Concelman connector (BNC), and fiber optic. Unshielded twisted pair (UTP) cable typically uses an RJ connector that is attached to the UTP cable using a crimping tool. Crimping connects the wire strands inside the cable to the metal pins of the connector, and secures the cable inside the connector plug.
- 109. Study Notes http://SlideShare.net/OxfordCambridge 109| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Typical RJ connector types used are RJ-11 or RJ-45. RJ-11 RJ-45 RJ-11 RJ-11 connectors consist of four wires, two pairs. They are mainly used in phone lines, but are sometimes used in local area networks (LANs) also.
- 110. Study Notes http://SlideShare.net/OxfordCambridge 110| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n RJ-45 The RJ-45 is an eight-wire, or four-pair, connector. It is typically used with UTP cables to connect computers to Ethernet LANs. The RJ-45 connectors are wider than the RJ-11, but are quite similar in appearance otherwise.
- 111. Study Notes http://SlideShare.net/OxfordCambridge 111| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n There are three types of connector normally associated with coaxial cable. These include Bayonet Neill- Concelman connector (BNC), the F-type connector, and AUI/DB. In the AUI/DB connector, the letters AUI refer to Attachment Unit Interface. The following connectors are used with coaxial cable.
- 112. Study Notes http://SlideShare.net/OxfordCambridge 112| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n AUI/DB-15 BNC F-Type AUI/DB-15 AUI/DB-15 connectors are used with RG-8 thick Ethernet cable, commonly called Thicknet. Workstations are connected to an external transceiver using a 15-pin "D" shaped AUI connector. This is plugged into a socket on the network interface card (NIC) of the workstation. This transceiver is connected to a vampire tap, which is clamped onto the main Thick Ethernet cable. Vampire taps are given this name because the connection with the inner conductor of the cable is made by a metal tooth that sinks into the cable. N-series connectors, which have a male/female screw-and-barrel configuration, are also used with some Thick Ethernet cables.
- 113. Study Notes http://SlideShare.net/OxfordCambridge 113| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n BNC Bayonet Neill-Concelman connector (BNC) is used with Thinnet, or RG-58 Thin Ethernet cables. It has male and female type connectors and the male connector is attached to each end of a cable. You can attach it using a crimper or a screw-on connection, although you should avoid using the screw-on type of connector as it is unreliable. The male connector consists of a center pin connected to the center conductor of the cable and a metal tube connected to the outer shield of the cable. There is also a rotating ring outside the tube that locks the cable onto any female connector, using a quarter-twist motion. F-Type F-type is a threaded coaxial signal connector that is typically used with coaxial cable for connecting to wireless access points or bridges. It is inexpensive since the pin of the connector is also the center conductor and is simple to install. An F-type connector can normally be used up to frequencies of 1 GHz. Quizxxx Which type of cable connector is used to connect Thinnet coaxial cable?
- 114. Study Notes http://SlideShare.net/OxfordCambridge 114| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Options: 1. AUI/DB-15 2. BNC 3. F-type 4. RJ-45 2. Fiber optic cable connectors Fiber optic cable connectors are mechanical devices connected to the end of a single-mode or multimode fiber optic cable. Fiber optic cable connectors should be capable of being easily attached to, and detached from, equipment. The following are some of the fiber optic cable connector types available. Subscriber Connector (SC) Straight Tip (ST) Local Connector (LC) MT-RJ
- 115. Study Notes http://SlideShare.net/OxfordCambridge 115| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Subscriber Connector (SC) Subscriber Connector (SC), also known as a square connector, is low cost, simple, and durable. It is a duplex, latched connector – which means that the connection has to be released, usually by pressing a button or a release. The SC is one of the most common type of fiber optic connectors used. Straight Tip (ST) The Straight Tip (ST) fiber optic connector is widely used. It has a metal connector housing similar to a coaxial Thinnet BNC connector. There are two versions of ST connectors available – ST and ST-II. They are keyed and spring-loaded and can be push-in or twist-type connectors. Local Connector (LC) The Local Connector (LC) has a plastic housing and a locking tab, and provides accurate alignment of the fibers. It is used with fiber optic line equipment and in termination cabinets.
- 116. Study Notes http://SlideShare.net/OxfordCambridge 116| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n MT-RJ The MT-RJ connector was designed to replace the Subscriber Connector. It has a plastic housing and is about half the size of the SC. It is a two-fiber connector, providing accurate alignment using internal metal guide pins. Quizxxxi This connector is the most widely used fiber optic connector. It has a metal housing similar to the coaxial BNC attachment mechanism with Thinnet. Identify the fiber optic cable connector type described here.
- 117. Study Notes http://SlideShare.net/OxfordCambridge 117| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Options: 1. Local Connector (LC) 2. MT-RJ 3. Straight Tip (ST) 4. Subscriber Connector (SC) 3. The IEEE 1394 standard The Institute of Electrical and Electronics Engineers (IEEE) 1394 standard is a method of connecting digital devices. It is a bus standard that supports data transfer rates of up to 400 Mbps (using IEEE 1394a), or 800 Mbps (using IEEE 1394b). The names of the products that support the IEEE 1394 standard can vary. Two of the most popular are FireWire and i.link. FireWire is produced by Apple, who originally developed the technology. The IEEE 1394 standard has a number of advantages: a high-speed data transfer rate a highly compatible Input/Output (I/O) connection method non-proprietary method of interconnecting digital devices delivery of data at a guaranteed rate support to both hot plugging and Plug-and-Play provision of power to peripheral devices IEEE 1394 has a flexible peer-to-peer topology and scalable architecture. This makes it suitable for connecting devices that have real-time multimedia processing requirements.
- 118. Study Notes http://SlideShare.net/OxfordCambridge 118| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n The IEEE 1394 standard provides power to peripheral devices – a single port can be used to connect up to 63 external devices. It delivers data at a guaranteed rate. For example, with multimedia products, it is vital that data is delivered as fast as it is displayed. It is also important that video and audio are synchronized. The IEEE 1394 standard supports hot plugging, allowing you to add and remove devices to a computer as required, without having to shut the system down. With the IEEE 1394, you can plug in a device and immediately use it (known as Plug-and-Play) – and the operating system automatically recognizes this. Quizxxxii What is the maximum data transfer rate that the IEEE 1394b sub-standard supports? Options: 1. 200 Mbps 2. 600 Mbps 3. 800 Mbps
- 119. Study Notes http://SlideShare.net/OxfordCambridge 119| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Summary Cable connectors differ in modern networks depending on the cable type. Unshielded twisted pair (UTP) cable normally uses a Registered Jack (RJ) connector, which is attached using a crimper. This can be an RJ-11 or an RJ-45. By contrast, coaxial cable often uses Attachment Unit Interface (AUI)/DB-15, Bayonet Neill-Concelman connector (BNC) or F-Type connectors. There are a number of fiber optic cable connectors available also--the one you choose depends on what you are using it for. The most common types are Subscriber Connector (SC), Straight Tip (ST), Local Connector (LC), and MT-RJ. Digital devices can be connected using the Institute of Electrical and Electronics Engineers (IEEE) 1394 standard--it supports data transfer rates of up to 400Mbps (using IEEE 1394a), or 800Mbps (using IEEE 1394b). The products that support the standard are known by various names, but two of the most popular products are FireWire (which is made by Apple), and i.link.
- 120. Study Notes http://SlideShare.net/OxfordCambridge 120| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n K. Network installation tools After completing this section, you should be able to determine the most appropriate network tool to use in a given scenario. 1. Patch panels and wiring tools 2. Media testing tools 1. Patch panels and wiring tools A patch panel is a centralized wiring point for multiple devices on an unshielded twisted pair (UTP) network. It does not contain any electronic circuits. You can also use a patch panel to connect the cables going to the hub with the cables going to computer ports. When you are using a patch panel in a UTP network, you connect the long run of network cable from the workstation into the patch panel and then connect the corresponding patch panel port into the network hub.
- 121. Study Notes http://SlideShare.net/OxfordCambridge 121| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n A patch cable is a network cable that connects, or patches, ports on network devices together. For example, patch cables connect a workstation to the floor or wall network socket, and then a drop cable is used to connect the socket to the patch panel. Another patch cable is then used to connect the patch panel to the network hub. When wiring networks, the total segment length of the network should include the patch cables at both ends and the drop cable in between. For example, say you are using 100BaseT Ethernet over category 5 UTP cables in the configuration - and the maximum segment length is 100 meters. This means that the maximum distance from the hub to each network interface card (NIC) is 100 meters. You should ensure that the following is less than 100 meters long in total: the cable from the hub to the patch panel plus the drop cable to the wall socket plus the cable from the wall socket to the workstation Otherwise, the connected workstation may not be able to communicate correctly with the rest of the network.
- 122. Study Notes http://SlideShare.net/OxfordCambridge 122| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Note:make sure that you match or exceed the rating of the cabling when putting a patch panel into a network. For example, using a Category 3 patch panel with category 5 cabling will cause the entire network to operate as a category 3 network. The following are two of the tools that are used to attach connectors to the ends of network cables. Wire crimper Punchdown tool Wire crimper A wire crimper, or crimper, is a hand tool. It attaches connectors to the ends of any type of network cable. It uses pressure to press metal teeth into the inner wires of the cable. This process is called crimping. Punchdown tool A punchdown tool is a hand tool and is used to punch the cable down into an insulation displacement connector (IDC), typically used in patch panels. The IDC displaces, or cuts through, the insulation of one of the conductors inside a twisted pair cable. The tool presses the conductor against the sides of a metal "V" in the IDC. This creates a connection between the inner conductor of the wire and the small metal "knife" in the connector. Twisted pair cables are terminated at patch panels in a wiring closet using a punchdown tool.
- 123. Study Notes http://SlideShare.net/OxfordCambridge 123| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Not to forget that patch panels have the following advantages: they provide a convenient place to connect together all the cables that come from different ports they enable you to upgrade networks and troubleshoot more easily they help you avoid physical damage to the cable, because it isn't necessary to move the patch panel when you upgrade the network Quizxxxiii Which of these tasks would you perform using a punchdown tool? Options: 1. Attaching connectors onto different types of network cables 2. Connecting the patch panel port to the hub 3. Attaching twisted pair cables to an IDC 2. Media testing tools The type of network testing tools you choose depends on the type of cable your network uses. The following are some of the tools used for network testing. Wire map tester Continuity tester Tone generator Optical loss test set (OLTS) Multifunction cable tester
- 124. Study Notes http://SlideShare.net/OxfordCambridge 124| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Wire map tester A wire map tester determines if a copper twisted pair cable is connected to the correct pin by transmitting a signal through each wire. It detects all problems that can render a length of cable unable to be used - such as transposed wires, and open and short circuits. Wire mapping is the most basic of the tests for twisted pair cables, because the wire connections in each cable are a very common source of installation errors. Wire map testing is almost always included in multifunction cable testers, but it may not be necessary to spend large amounts of money on a comprehensive device. A dedicated wire map tester is relatively inexpensive and enables you to test your installed cabling for the
- 125. Study Notes http://SlideShare.net/OxfordCambridge 125| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n most common faults that occur during and after installation. For example, if you are installing voice-grade cable, you may only need to carry out a wire mapping test. A wire map tester consists of two parts. It has a remote unit that you attach to one end of the connection and a battery operated handheld main unit that displays the results. Normally, the hand-held unit displays a series of lights or codes describing the type of fault it found. Some testers have multiple numbered remote units for easier testing of several connections, without traveling repeatedly to move the remote unit. Split pairs are not detectable by a dedicated wire map tester – although the pinouts are incorrect, the cable is still wired straight through. Continuity tester A continuity tester is a simple device and is less expensive than a wire map tester. It checks a copper cable connection for basic installation problems, such as opens, shorts, and crossed pairs. They are inexpensive and, as a result, cannot normally detect complicated faults - for example, split pairs. However, they are adequate for basic cable testing, particularly for coaxial cables. A continuity tester consists of two separate parts and you connect one part to each end of the cable that is being tested. Normally, the two separate units can be connected together for easy testing of patch cables and for storage. Tone generator The tone generator and probe, or fox and hound wire tracer, is the simplest type of copper cable tester. It consists of two parts - one part that you connect to the cable and the other part which is a penlike probe. The first part is connected with a standard jack if a cable is being tested. If it is an individual wire, however, you use alligator clips, and it transmits a signal over the wire or cable. When the probe part is touched to the other end of the wire, cable, or insulating sheath, it emits an audible tone. The tone generator and probe is most popularly used to locate a specific connection in a punchdown block.
- 126. Study Notes http://SlideShare.net/OxfordCambridge 126| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n It can also be used to identify a particular cable at any point between the two ends - for example, in a bundle of cables in a ceiling conduit. To do this, you should connect the tone generator to one end and touch the probe to each cable in the bundle until there is an audible tone. It is possible to use a tone generator and probe to locate open wires, short wires, and miswires. This can be done by testing the continuity of the individual wires on the circuit. An open wire would produce no tone at the other end, while a short would produce a tone on multiple wires at the other end. An improperly connected wire would produce a tone on the wrong pin at the other end. However, this is extremely time consuming and very prone to errors. You need to either repeatedly travel from one end of the cable to the other to move the tone generator unit, or have a partner test each connection and keep in close contact with that person to avoid confusion. Considering the time and effort involved, using a wire map tester is a more practical solution for locating opens, shorts, and miswires. Optical loss test set (OLTS) An optical loss test set (OLTS) is a combined optical power meter and test source. These two devices are needed to be able to properly install and troubleshoot a fiber optic network.
- 127. Study Notes http://SlideShare.net/OxfordCambridge 127| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n You install the light source to one end of the cable and the power meter to the other end to carry out the testing. Since an OLTS is a combined unit, two units are required to test permanently installed cables and to carry out field testing. Although two OLTS units are required for some testing, the power meter and light source are designed to work together and normally cost less than two separate devices. Multifunction cable tester Multifunction cable testers, or certification tools, perform a series of tests on a length of cable and return a series of pass or fail results. They can operate on either copper or fiber optic cables. Multifunction cable testers base the pass or fail results on pre-programmed standards or values or on user inputted parameters. Multifunction cable testers are very simple-to-use devices and can be used by people who do not understand the tests being carried out or the results produced, because only pass or fail readings are given by the device.
- 128. Study Notes http://SlideShare.net/OxfordCambridge 128| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n However, although multifunction cable testers are simple to use, the fact that they do not output the raw data of the results from the tests means that you must trust the manufacturer and that the device is analyzing the results correctly. Also, the standards that are used by some of the devices are not necessarily reliable because some cable types - for example, Category 6 and 7 cables might not have been ratified yet. When purchasing a multifunction cable tester, you should purchase a unit that is upgradable or can be manually configured so that the device can keep up with the constantly evolving standards. Quizxxxiv Suppose you've just installed a section of UTP cable in your company's network. Now you want to test the cable to make sure that the connector wiring is correct. Which tool should you use? Options: 1. Wire map tester 2. Continuity tester 3. Tone generator 4. OLTS Summary A patch panel is a centralized wiring point for multiple devices on an unshielded twisted pair (UTP) network. You use a patch panel to connect the cables going to the network hub with the cables going to the workstations. You connect components to a patch panel using patch cables and the total segment length of the network includes the patch cables at both ends and the drop cable between. Wire crimpers and punchdown tools can be used to connect network cables to connectors and patch panels. There are a number of different network testing tools and the type you choose depends on the type of
- 129. Study Notes http://SlideShare.net/OxfordCambridge 129| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n cabling in your network, cost, and what you are testing it for. The most popular types of testing tools are the wire map tester, continuity tester, tone generator, optical loss test set (OLTS), and the multifunction cable tester. There are also fiber optic patch panels, as illustrated below.
- 130. Study Notes http://SlideShare.net/OxfordCambridge 130| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n L. Connecting the network (exercise) After completing this section, you should be able to determine the appropriate network media and connectors to use in a given scenario. Exercise overview Task 1: Choosing a network media type | Task 2: Recognizing media specifications Task 3: Recognizing cable connector types Exercise overview In this exercise, you're required to choose a specific network media type in a given scenario, recognize the specifications of each media type, and recognize cable connector types. This involves the following tasks: choosing a network media type recognizing media specifications recognizing cable connector types Task 1: Choosing a network media type You are a network engineer for Oxford Computing Ltd. Your task is to examine new cabling requirements for the network and suggest appropriate network media types. Oxford Computing Ltd is a multinational company so it is important that data can be exchanged between the head office and branches, both proximate and remote. The nearest branch office is 450 meters away and needs to be connected without undue cost. In some cases, there is no physical medium connecting a branch to the head office.
- 131. Study Notes http://SlideShare.net/OxfordCambridge 131| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n The head office is a four-storey building with workgroup switches on each floor. The priority is that data exchange rates between workgroup switches in the main office must be over 100 Mbps. Complex cable that runs from floor to floor will involve lengths of approximately 150 meters. The cable connecting the devices on each floor won't be required to cover distances of over 45 meters, and must be inexpensive to purchase. In addition, the media type you choose to use needs to run with minimum disruption to the building infrastructure. Step 1 of 1 Match the media types to the relevant positions on this network. Options: 1. Coaxial 2. Fiber optic 3. Unshielded twisted pair 4. Wireless Targets: A. This media type is able to cover 450 meters or more, and is resistant to EMI. B. This media type has data exchange rates of up to 100 Gbps and will cover distances over 100 meters. C. This media type is inexpensive, easy to install, and covers a distance of 45 meters. D. This media type allows you exchange data with devices where no physical medium exists. Result Coaxial cable is able to cover 450 meters or more and is resistant to electromagnetic interference. Fiber optic cable has data exchange rates of up to 100 Gbps and can cover distances well over 100 meters. UTP is the cheapest media type – it is easy to install, and can cover a distance up to 100 meters. Wireless media allow you to exchange data with devices where no physical medium exists.
- 132. Study Notes http://SlideShare.net/OxfordCambridge 132| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Even though unshielded twisted pair (UTP) is less expensive than coaxial and shielded twisted pair (STP) is resistant to electromagnetic interference (EMI), neither UTP nor STP can cover distances of over 100 meters. Coaxial cable is also cheaper to install than fiber optic cable. Even though it is expensive to install, fiber optic cable provides faster data exchange rates than coaxial and twisted pair cabling. UTP cable is the least expensive cable type and is compatible with most major networking architectures. Because it is flexible, UTP cable is easy to install. Wireless signals are electromagnetic waves that can travel through the vacuum of outer space and through a medium such as air. You are now familiar with choosing a specific network media type for a given scenario. Task 2: Recognizing media specifications You've identified UTP cabling as being suitable for connecting workstations on each floor to the workgroup switch for that floor. Step 1 of 3 Identify the true statements about twisted pair cabling. Options: 1. STP is less expensive than UTP 2. STP is more resistant to EMI than UTP 3. UTP has the ability to reduce interference 4. UTP is compatible with most of the major networking architectures
- 133. Study Notes http://SlideShare.net/OxfordCambridge 133| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Result UTP has the ability to reduce interference and is compatible with most of the major networking architectures. STP is more resistant to EMI than UTP. Option 1 is incorrect. UTP and STP are the least expensive media for data communication. However, UTP is less expensive than STP. Option 2 is correct. STP also reduces electrical noise within the cable (pair-to-pair coupling, or crosstalk). Option 3 is correct. The twisted wire pairs in UTP reduce the risk of signal degradation from EMI and radio frequency interference (RFI). Option 4 is correct. Because of its small cable diameter and the fact that it can be used with most of the major networking architectures, UTP cable continues to grow in popularity. Coaxial cable (Thicknet) can be used to connect the head office to the branch office situated less than half a kilometer away. Step 2 of 3 Identify the true statements about coaxial cables. Options: 1. Coaxial cable supports 10 to 100 Mbps 2. Thicknet cable is used in most networking architectures 3. Thinnet cable is commonly used in Ethernet networks 4. Thinnet cable is especially useful for cable installations that require the cable to make many twists and turns Result Coaxial cable supports 10 to 100 Mbps, and Thinnet cable is especially useful for cable installations that require the cable to make many twists and turns. Option 1 is correct. Coaxial, UTP, and STP can reach speeds of up to 100 Mbps. Option 2 is incorrect. Because of its wide diameter and the fact that the cable isn't very pliable, Thicknet cable is difficult to install and is almost never used except for special-purpose installations.
- 134. Study Notes http://SlideShare.net/OxfordCambridge 134| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Option 3 is incorrect. Though initially designed for Ethernet networks, Thinnet cable proved troublesome to install, resulting in electrical interference. Therefore, Thinnet cable is no longer commonly used in Ethernet networks. Option 4 is correct. Thinnet cable's small diameter makes it easier for installers to negotiate twists and turns. You have specified that fiber optic cable be used to connect the workgroup switches between floors. The branches not connected by physical media to the head office can utilize wireless communication. Step 3 of 3 Identify the true statements about wireless communication. Options: 1. Low frequency electromagnetic waves have a short wavelength 2. Radio frequencies (RFs) can be used to transmit data between devices on a LAN 3. A wireless hub is used for signal distribution 4. Because there are no cables involved, workstations do not need a NIC Result Wireless communication can use RFs to transmit data between devices on a LAN. A wireless hub is used for signal distribution. Option 1 is incorrect. Wavelength is the distance from one peak to the next on the sine wave. Low frequency electromagnetic waves have a long wavelength. Option 2 is correct. Wireless communication also uses infrared waves to transmit data between devices on a LAN. Option 3 is correct. A wireless hub serves as the access point where PCs and laptops connect to the network. Option 4 is incorrect. To receive the signals from a wireless hub, a PC or laptop needs to have a wireless adapter card, or wireless NIC installed. You are now familiar with the specifications of the different media that are available.
- 135. Study Notes http://SlideShare.net/OxfordCambridge 135| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Task 3: Recognizing cable connector types You've already selected the appropriate media type for each section of the network. Now you need to connect the cables to the devices in your network. Step 1 of 4 Identify the connector type you could use on the UTP cabling to connect the workstations on each floor to the workgroup switch for that floor. Options: 1. BNC 2. MT-RJ 3. RJ-11 4. RJ-45 Result RJ-45 connectors are used to connect the workstations on each floor to the workgroup switch for that floor. Option 1 is incorrect. British Naval Connector (BNC) is used with Thinnet, or RG-58 Thin Ethernet cables. You can attach the connectors to the cables using a crimper or a screw-on connection. The screw-on type of connector is unreliable so you should avoid using it. Option 2 is incorrect. The MT-RJ connector is a fiber optic cable connector. Option 3 is incorrect. An RJ-11 connector is used to connect phones to a PSTN or POTS networks. Option 4 is correct. The RJ-45 is an eight-wire, or four-pair, connector. It is typically used to connect computers to Ethernet LANs with UTP cabling.
- 136. Study Notes http://SlideShare.net/OxfordCambridge 136| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Step 2 of 4 Identify the connector types you could use on the coaxial cable (Thicknet) used to connect the head office to the branch office that lies less than half a kilometer away. Options: 1. AUI/DB-15 2. F-Type 3. Subscriber Connector (SC) Result You can use AUI/DB-15 and F-Type connector types with coaxial cable (Thicknet). Option 1 is correct. AUI/DB-15 connectors are used with RG-8 thick Ethernet cable. The letters AUI refer to Attachment Unit Interface. Workstations are connected to an external transceiver using a 15-pin "D" shaped AUI connector. This is plugged into a socket on the NIC of the workstation. The transceiver is then connected to a vampire tap which is clamped onto the main Thick Ethernet cable. Option 2 is correct. F-type is a threaded coaxial signal connector. It is inexpensive because the pin of the connector is also the center conductor and is simple to install. An F-type connector can normally be used up to frequencies of 1 GHz. Option 3 is incorrect. SC is a low cost, simple, and durable connector type used with fiber optic cable.
- 137. Study Notes http://SlideShare.net/OxfordCambridge 137| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Step 3 of 4 Identify the true statements about fiber optic cables. Options: 1. Fiber optic cable is more expensive than coaxial 2. Multimode fiber optic cable is often used for campus backbones 3. Single-mode fiber optic cable is often used for workgroup applications 4. The maximum cable length of single-mode cable is 60 kilometers Result Fiber optic cable is more expensive than coaxial cabling, and the maximum cable length of single-mode cable is 60 kilometers. Option 1 is correct. Although it is more expensive than UTP and STP, fiber optic cannot be tapped. It can be used over great distances and is not susceptible to electromagnetic interference (EMI). Option 2 is incorrect. Multimode cable uses light emitting diodes (LEDs) as light-generating devices and is often used for workgroup applications. Option 3 is incorrect. Because it is capable of higher bandwidth and can support greater distances than multimode, single-mode is often used for campus backbones. Option 4 is correct. Multimode cable can support cables for up to two kilometers only, whereas the maximum cable length of single-mode cable is 60 kilometers. Step 4 of 4 Identify the connector types you could use on the fiber optic cable used to connect the workgroup switches between floors. Options: 1. Local Connector (LC) 2. MT-RJ 3. N-series
- 138. Study Notes http://SlideShare.net/OxfordCambridge 138| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n 4. Straight Tip (ST) Result ST, LC, and MT-RJ are fibre optic cable connectors that you could use to connect the workgroup switches between floors. Option 1 is correct. The LC fibre optic connector has a plastic housing and a locking tab, and provides accurate alignment of the fibers. Option 2 is correct. The MT-RJ connector has a plastic housing and is a two-fiber connector, providing accurate alignment using internal metal guide pins. Option 3 is incorrect. N-series connectors are used with some Thick Ethernet cables. They have a male/female screw-and-barrel configuration. Option 4 is correct. The ST connector is the most widely used fiber optic connector. It has a metal connector housing similar to a coaxial Thinnet BNC connector. There are two versions of ST connectors available – ST and ST-II. Understanding the types of media that can be used within a network provides you with a better understanding of how networks function, and allows you to select the most suitable means of connecting your network devices. You are now familiar with the different cable connector types available.
- 139. Study Notes http://SlideShare.net/OxfordCambridge 139| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n IV. Annexes: The OSI model Illustrated Glossary Answers to Quizzes
- 140. Study Notes http://SlideShare.net/OxfordCambridge 140| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n The OSI model Illustrated
- 141. Study Notes http://SlideShare.net/OxfordCambridge 141| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n
- 142. Study Notes http://SlideShare.net/OxfordCambridge 142| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n
- 143. Study Notes http://SlideShare.net/OxfordCambridge 143| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n M. Glossary ABR Acronym for available bit rate. See UBR. access list List kept by Cisco routers to control access to or from the router for a number of services (for example, to prevent packets with a certain IP address from leaving a particular interface on the router). acknowledgment Notification sent from one network device to another to acknowledge that some event (for example, receipt of a message) has occurred. Sometimes abbreviated ACK. active hub Multiport device that amplifies LAN transmission signals. adapter An adapter is a physical device that allows one hardware or electronic interface to be adapted (accommodated without loss of function) to another hardware or electronic interface. In a computer, an adapter is often built into a card that can be inserted into a slot on the computer's motherboard. The card adapts information that is exchanged between the computer's microprocessor and the devices that the card supports. adaptive routing See dynamic routing. address Data structure or logical convention used to identify a unique entity, such as a particular process or network device. Address Resolution Protocol Abbreviated to ARP. administrative distance A rating of the trustworthiness of a routing information source. In Cisco routers, administrative distance is expressed as a numerical value between 0 and 255. The higher the value, the lower the trustworthiness rating. ADSL Acronym for asymmetric digital subscriber line. One of four DSL technologies. ADSL is designed to deliver more bandwidth downstream (from the central office to the customer site) than upstream. Downstream rates range from 1.5 to 9 Mbps, while upstream bandwidth ranges from 16 to 640 kbps. ADSL transmissions work at distances up to 18,000 feet (5,488 meters) over a single copper twisted pair. algorithm Well-defined rule or process for arriving at a solution to a problem. In networking, algorithms are commonly used to determine the best route for traffic from a particular source to a particular destination. American National Standards Institute See ANSI. American Standard Code for Information Interchange See ASCII ANSI Acronym for American National Standards Institute. Voluntary organization comprised of corporate, government, and other members that coordinates standards-related activities, approves U.S. national standards, and develops positions for the United States in international standards organizations. ANSI helps develop international and U.S. standards relating to, among other things, communications and networking. ANSI is a member of the IEC and the ISO. API Acronym for application programming interface. Specification of function-call conventions that defines an interface to a service. application layer Layer 7 of the OSI reference model. This layer provides services to application processes (such as electronic mail, file transfer, and terminal emulation) that are outside of the OSI model. The application layer identifies and establishes the availability of intended communication partners (and the resources required to connect with them), synchronizes cooperating applications, and establishes agreement on procedures for error recovery and control of data integrity. Corresponds roughly with the transaction services layer in the SNA model. application programming interface See API.
- 144. Study Notes http://SlideShare.net/OxfordCambridge 144| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n ARP Acronym for Address Resolution Protocol. Internet protocol used to map an IP address to a MAC address. Defined in RFC 826. Compare with RARP. ASCII Acronym for American Standard Code for Information Interchange. 8-bit code for character representation (7 bits plus parity). asymmetric digital subscriber line Abbreviated to ADSL. asynchronous transmission Term describing digital signals that are transmitted without precise clocking. Such signals generally have different frequencies and phase relationships. Asynchronous transmissions usually encapsulate individual characters in control bits (called start and stop bits) that designate the beginning and end of each character. ATDM Acronym for asynchronous time-division multiplexing. Method of sending information that resembles normal TDM, except that time slots are allocated as needed rather than preassigned to specific transmitters. See FDM. ATM Acronym for Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3. attachment unit interface See AUI. attenuation Loss of communication signal energy. attribute Configuration data that defines the characteristics of database objects such as the chassis, cards, ports, or virtual circuits of a particular device. Attributes might be preset or user-configurable. AUI Attachment unit interface. IEEE 802.3 interface between an MAU and a NIC (network interface card). The term AUI can also refer to the rear panel port to which an AUI cable might attach, such as those found on a Cisco LightStream Ethernet access card. Also called transceiver cable. autonomous system Collection of networks under a common administration sharing a common routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned a unique 16-bit number by the IANA. Sometimes abbreviated AS. back end Node or software program that provides services to a front end. Usually transparent to the user. backbone The part of a network that acts as the primary path for traffic that is most often sourced from, and destined for, other networks. backbone cabling Cabling that provides interconnections between wiring closets, wiring closets and the POP, and between buildings that are part of the same LAN. Also known as vertical cabling. backplane The backplane is a large circuit board that contains sockets for expansion cards. bandwidth The difference between the highest and lowest frequencies available for network signals. The term is also used to describe the rated throughput capacity of a given network medium or protocol. baseband Characteristic of a network technology where only one carrier frequency is used. Ethernet is an example of a baseband network. Also called narrowband. Basic Rate Interface See BRI. baud Unit of signaling speed equal to the number of discrete signal elements transmitted per second. Baud is synonymous with bits per second (bps), if each signal element represents exactly 1 bit.
- 145. Study Notes http://SlideShare.net/OxfordCambridge 145| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n B-channel The name for a bearer channel. DS0 time slot that carries analog voice or digital data over ISDN. In ISDN, a full-duplex, 64-kbps channel used to send user data. BECN Acronym for backward explicit congestion notification. Bit set by a Frame Relay network in frames traveling in the opposite direction of frames encountering a congested path. DTE receiving frames with the BECN bit set can request that higher-level protocols take flow control action as appropriate. Compare with FECN. BGP Acronym for Border Gateway Protocol. Interdomain routing protocol that replaces EGP. BGP exchanges reachability information with other BGP systems. It is defined by RFC 1163. BGP4 BGP Version 4. Version 4 of the predominant interdomain routing protocol used on the Internet. BGP4 supports CIDR and uses route aggregation mechanisms to reduce the size of routing tables. Bit The smallest unit of data in a computer. A bit equals 1 or 0, and is the binary format in which data is processed by computers. Border Gateway Protocol See BGP. BPDU Acronym for bridge protocol data unit. Spanning-Tree Protocol hello packet that is sent out at configurable intervals to exchange information among bridges in the network. BRI Acronym for Basic Rate Interface. ISDN interface composed of two B channels and one D channel for circuit-switched communication of voice, video, and data. bridge Device that connects and passes packets between two network segments that use the same communications protocol. Bridges operate at the data-link layer (Layer 2) of the OSI reference model. In general, a bridge will filter, forward, or flood an incoming frame based on the MAC address of that frame. bridge protocol data unit See BPDU. broadband Transmission system that multiplexes multiple independent signals onto one cable. In telecommunications terminology, any channel having a bandwidth greater than a voicegrade channel (4 kHz). In LAN terminology, a coaxial cable on which analog signaling is used. Also called wideband. broadcast Data packet that will be sent to all nodes on a network. Broadcasts are identified by a broadcast address. Compare with multicast and unicast. broadcast address Special address reserved for sending a message to all stations. Generally, a broadcast address is a MAC destination address of all ones. broadcast domain The set of all devices that will receive broadcast frames originating from any device within the set. Broadcast domains are typically bounded by routers because routers do not forward broadcast frames. broadcast storm Undesirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth and, typically, causes network time-outs. buffer Storage area used for handling data in transit. Buffers are used in internetworking to compensate for differences in processing speed between network devices. Bursts of data can be stored in buffers until they can be handled by slower processing devices. Sometimes referred to as a packet buffer. bus A bus is a collection of wires through which data is transmitted from one part of a computer to another. The bus connects all the internal computer components to the CPU. The ISA and the PCI are two types of buses. bus topology
- 146. Study Notes http://SlideShare.net/OxfordCambridge 146| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Linear LAN architecture in which transmissions from network stations propagate the length of the medium and are received by all other stations. byte A byte is a unit of measure used to describe the size of a data file, the amount of space on a disk or other storage medium, or the amount of data being sent over a network. One byte equals eight bits of data. cable Transmission medium of copper wire or optical fiber wrapped in a protective cover. catchment area Zone that falls within area that can be served by an internetworking device such as a hub. Category 1 cabling One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 1 cabling is used for telephone communications and is not suitable for transmitting data. Category 2 cabling One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 2 cabling is capable of transmitting data at speeds up to 4 Mbps. Category 3 cabling One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 3 cabling is used in 10BASE-T networks and can transmit data at speeds up to 10 Mbps. Category 4 cabling One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 4 cabling is used in Token Ring networks and can transmit data at speeds up to 16 Mbps. Category 5 cabling One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 5 cabling is used for running CDDI and can transmit data at speeds up to 100 Mbps. CDDI Acronym for Copper Distributed Data Interface. Implementation of FDDI protocols over STP and UTP cabling. CDDI transmits over relatively short distances (about 100 meters), providing data rates of 100 Mbps using a dual-ring architecture to provide redundancy. Based on the ANSI Twisted-Pair Physical Medium Dependent (TPPMD) standard. See FDDI. CDP Acronym for Cisco Discovery Protocol. Media- and protocol-independent device-discovery protocol that runs on all Cisco- manufactured equipment by default including routers, access servers, bridges, and switches. Using CDP, a device can advertise its existence to other devices and receive information about other devices on the same LAN or on the remote side of a WAN. Runs on all media that support SNAP, including LANs, Frame Relay, and ATM media. CDP is a Layer 2 multicast technology. cell The basic unit for ATM switching and multiplexing. Cells contain identifiers that specify the data stream to which they belong. Each cell consists of a 5-byte header and 48 bytes of payload. cell switching Network technology based on the use of small, fixed-size packets, or cells. Because cells are fixed-length, they can be processed and switched in hardware at high speeds. Cell relay is the basis for many high-speed network protocols including ATM, IEEE 802.6, and SMDS. channelized T1 Access link operating at 1.544 Mbps that is subdivided into 24 channels (23 B-channels and 1 D-channel) of 64 Kbps each. The individual channels or groups of channels connect to different destinations. Supports DDR, Frame Relay, and X.25. Also referred to as fractional T1. CHAP Acronym for Challenge Handshake Authentication Protocol. Security feature supported on lines using PPP encapsulation that prevents unauthorized access. CHAP does not itself prevent unauthorized access, it merely identifies the remote end. The router or access server then determines whether that user is allowed access. checksum Method for checking the integrity of transmitted data. A checksum is an integer value computed from a sequence of octets taken through a series of arithmetic operations. The value is recomputed at the receiving end and compared for verification. CIR
- 147. Study Notes http://SlideShare.net/OxfordCambridge 147| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Acronym for committed information rate. The rate at which a Frame Relay network agrees to transfer information under normal conditions, averaged over a minimum increment of time. CIR, measured in bits per second, is one of the key negotiated tariff metrics. circuit switching Switching system in which a dedicated physical circuit path must exist between sender and receiver for the duration of the call. Used heavily in the telephone company network. Circuit switching can be contrasted with contention and token passing as a channelaccess method, and with message switching and packet switching as a switching technique. classful network Network that uses traditional IP network addresses of class A, class B, and class C. The network boundary is defined by using a prefix value that indicates the number of bits used for the network portion. classless network Network that does not use the traditional IP network addressing (class A, class B, and class C). The network boundary is defined by the use of a network mask or subnet mask and a logical "AND" operation between the subnet mask and IP address. Classless networks are more pervasive in today's networks because of flexibility and less wasted IP addresses. CLI Acronym for Command Language Interpreter. The basic Cisco IOS configuration and management interface. client Node or software program (front-end device) that requests services from a server. client-server model Common way to describe network services and the model user processes (programs) of those services. Examples include the nameserver/nameresolver paradigm of the DNS and fileserver/file-client relationships such as NFS and diskless hosts. CN Acronym for Content Network. A collection of devices that optimizes the delivery of Internet content (such as HTML documents and MPEG files) by caching content near clients, by proactively pushing content into those caches, and by routing each client request to the best device available at that moment to serve the particular content requested. coaxial cable Cable consisting of a hollow outer cylindrical conductor that surrounds a single inner wire conductor. Two types of coaxial cable are currently used in LANs: 50-ohm cable, which is used for digital signaling, and 75-ohm cable, which is used for analog signal and highspeed digital signaling. collapsed backbone Nondistributed backbone in which all network segments are interconnected by way of an internetworking device. A collapsed backbone might be a virtual network segment existing in a device such as a hub, a router, or a switch. collision In Ethernet, the result of two nodes transmitting simultaneously. The frames from each device impact and are damaged when they meet on the physical media. communication Transmission of information. compression The running of a data set through an algorithm that reduces the space required to store or the bandwidth required to transmit the data set. computer A device that computes. More recently, a device that can solve billions of equations per second. concentrator Any device that enables multiple physical or logical connections to be made at or to a single point. A hub is an example of a device that allows multiple physical connections into that single hub. conductor Any material with a low resistance to electrical current. Any material capable of carrying an electrical current. configuration register In Cisco devices, a 16-bit, user-configurable value that determines how the router functions during initialization. The configuration register can be stored in hardware or software. In hardware, the bit position is set using a jumper. In software, the bit position is set by specifying a hexadecimal value using configuration commands. congestion Traffic in excess of network capacity.
- 148. Study Notes http://SlideShare.net/OxfordCambridge 148| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n connectionless Term used to describe data transfer without the existence of a virtual circuit, error detection, and acknowledgments. connection-oriented Term used to describe data transfer with the existence of a virtual circuit, error detection, and acknowledgments. console DTE through which commands are entered into a host. The functionality can be provided for through a terminal device or application such as Telnet. contention Network media access method in which network devices compete for permission to access the physical medium. convergence The speed and ability of a group of internetworking devices running a specific routing protocol or Spanning-Tree Protocol to agree on the topology of an internetwork after a change in that topology. cost Arbitrary value, typically based on hop count, media bandwidth, or other measures, that is assigned by a network administrator and used to compare various paths through an internetwork environment. Cost values are used by Layer 2 and Layer 3 protocols, such as STP and routing protocols respectively, to determine the most favorable path to a particular destination: the lower the cost, the better the path. Sometimes called path cost. cps Acronym for cells per second. CPU Acronym for central processing unit. The CPU is the "brains" of the computer, where most of the calculations and processing take place. CRC Acronym for cyclic redundancy check. Error-checking technique in which the frame recipient calculates a remainder by dividing frame contents by a prime binary divisor and compares the calculated remainder to a value stored in the frame by the sending node. CSA Acronym for Canadian Standards Association. Agency within Canada that certifies products that conform to Canadian national safety standards. CSMA/CD Acronym for Carrier sense multiple access collision detect. Contention based Media-access mechanism wherein devices ready to transmit data first check the channel for a carrier. If no carrier is sensed for a specific period of time, a device can transmit. If two devices transmit at once, a collision occurs and is detected by all colliding devices. This collision subsequently delays retransmissions from those devices for some random length of time. CSMA/CD access is used by Ethernet and IEEE 802.3. CSU Acronym for channel service unit. Digital interface device that connects end-user equipment to the local digital telephone loop. Often referred to together with DSU, as CSU/DSU. data-link layer Layer 2 of the OSI reference model. This layer provides reliable transit of data across a physical link. The data-link layer is concerned with physical addressing, network topology, line discipline, error notification, ordered delivery of frames, and flow control. The IEEE has divided this layer into two sublayers: the MAC sublayer and the LLC sublayer. Sometimes simply called link layer. Roughly corresponds to the data-link control layer of the SNA model. DCE Data communications equipment (EIA expansion) or data circuit-terminating equipment (ITU-T expansion). The devices and connections of a communications network that comprise the network end of the user-to-network interface. The DCE provides a physical connection to the network, forwards traffic, and provides a clocking signal used to synchronize data transmission between DCE and DTE devices. Switches, modems and interface cards are examples of DCE. D-channel (data channel) Full-duplex, 16-kbps (BRI), or 64-kbps (PRI) ISDN channel used for call setup (BRI), control, and protocol negotiations. DDR Acronym for Dial-on-demand routing. Technique whereby a Cisco router can automatically initiate and close a circuit-switched session as transmitting stations demand. The router spoofs keepalives so that end stations treat the session as active. DDR permits routing over ISDN or telephone lines using an external ISDN terminal adaptor or modem. DECnet
- 149. Study Notes http://SlideShare.net/OxfordCambridge 149| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Group of communications products (including a protocol suite) developed and supported by Digital Equipment Corporation. DECnet/OSI (also called DECnet Phase V) is the most recent iteration and supports both OSI protocols and proprietary digital protocols. Phase IV Prime supports inherent MAC addresses that allow DECnet nodes to coexist with systems running other protocols that have MAC address restrictions. decryption The reverse application of an encryption algorithm to encrypted data, thereby restoring that data to its original, unencrypted state. default route Routing table entry that is used to direct frames for which a next hop is not explicitly listed in the routing table. demarc Demarcation point between carrier equipment and CPE. The point at which the service provider's local loop ends and the customer's network begins. demodulation Process of returning a modulated signal to its original form. Modems perform demodulation by taking an analog signal and returning it to its original (digital) form. demultiplexing The separating of multiple input streams that have been multiplexed into a common physical signal back into multiple output streams. DES Acronym for Data Encryption Standard. Standard cryptographic algorithm developed by the U.S. NBS. DNS Acronym for Domain Naming System. System used in the Internet for translating names of network nodes into IP addresses. domain In the Internet, a portion of the naming hierarchy tree that refers to general groupings of networks based on organization-type or geography. Also can be generally used to describe a logical grouping of networked devices that exhibit the same characteristics or use the same protocols. dot address Refers to the common notation for IP addresses in the form <a.b.c.d> where each number represents, in decimal, 1 byte of the 4-byte IP address. Also called dotted notation or four-part dotted notation. dotted decimal notation Syntactic representation for a 32-bit integer that consists of four 8-bit numbers written in base 10 with periods (dots) separating them. Used to represent IP addresses. DRAM Acronym for dynamic random-access memory. RAM that stores information in capacitors that must be periodically refreshed. DRAMs are less complex and have greater capacity than SRAMs. DS0 Digital signal level 0. Framing specification used in transmitting digital signals over a single channel at 64 kbps on an ISDN facility. DS1 Digital signal level 1. Framing specification used in transmitting digital signals at 1.544 Mbps on a T1 facility (in the U.S.) or at 2.048- Mbps on an E1 facility (in Europe). DS3 Digital signal level 3. Framing specification used for transmitting digital signals at 44.736 Mbps on a T3 facility and 34.368 on an E3 facility. DSU Acronym for data service unit. Device used in digital transmission that adapts the physical interface on a DTE device to a transmission facility such as T1 or E1. The DSU is also responsible for such functions as signal timing. Often referred to together with CSU, as CSU/DSU. DTE Acronym for data terminal equipment. Device at the user end of a user-network interface that serves as a data source, destination, or both. DTE connects to a data network through a DCE device (for example, a modem) and typically uses clocking signals generated by the DCE. DTE includes such devices as computers, routers, protocol translators, and multiplexers. dynamic random-access memory See DRAM.
- 150. Study Notes http://SlideShare.net/OxfordCambridge 150| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n dynamic routing Routing that adjusts automatically to network topology or traffic changes. Also called adaptive routing. Requires that a routing protocol be run between routers. E1 Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 2.048 Mbps. E1 lines can be leased for private use from common carriers. E3 Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 34.368 Mbps. E3 lines can be leased for private use from common carriers. EBCDIC Acronym for extended binary coded decimal interchange code. Any of a number of coded character sets developed by IBM consisting of 8-bit coded characters. This character code is used by older IBM systems and telex machines. EEPROM Acronym for Electrically Erasable Programmable Read-Only Memory. EPROM that can be erased using electrical signals applied to specific pins. EGP Acronym for Exterior Gateway Protocol. Internet protocol for exchanging routing information between autonomous systems. Documented in RFC 904. Not to be confused with the general term exterior gateway protocol. EGP is an obsolete protocol that has been replaced by BGP. EIA/TIA-232 Common physical-layer interface standard, developed by EIA and TIA, that supports unbalanced circuits at signal speeds of up to 64 kbps. Closely resembles the V.24 specification. Formerly known as RS-232. EIA/TIA-449 Popular physical-layer interface developed by EIA and TIA. Essentially, a faster (up to 2 Mbps) version of EIA/TIA-232 capable of longer cable runs. Formerly called RS-449. EIA/TIA-568 Standard that describes the characteristics and applications for various grades of UTP cabling. EIA/TIA-606 Administration standard for the telecommunications infrastructure of commercial buildings. It includes the following administration areas: terminations, media, pathways, spaces, bounding, and grounding. EIA-530 Refers to two electrical implementations of EIA/TIA-449: RS-422 (for balanced transmission) and RS-423 (for unbalanced transmission). EIGRP Acronym for Enhanced Interior Gateway Routing Protocol. Advanced version of IGRP developed by Cisco. Provides superior convergence properties and operating efficiency, and combines the advantages of link state protocols with those of distance vector protocols. EISA Acronym for Extended Industry-Standard Architecture. 32-bit bus interface used in PCs, PC-based servers, and some UNIX workstations and servers. EMI Acronym for electromagnetic interference. Interference by electromagnetic signals that can cause reduced data integrity and increased error rates on transmission channels. EMP Acronym for electromagnetic pulse. Caused by lightning and other high-energy phenomena. Capable of coupling enough energy into unshielded conductors to destroy electronic devices. encapsulation Device or software that modifies information into the required transmission format. encoding Process by which bits are represented by voltages. encryption
- 151. Study Notes http://SlideShare.net/OxfordCambridge 151| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n The application of a specific algorithm to data so as to alter the appearance of the data making it incomprehensible to those who are not authorized to see the information. end of transmission See EOT. Enhanced Interior Gateway Routing Protocol See EIGRP. enterprise network Large and diverse network connecting most major points in a company or other organization. Differs from a WAN in that it is privately owned and maintained. EOT Acronym for end of transmission. Generally, a character that signifies the end of a logical group of characters or bits. EPROM Acronym for erasable programmable read-only memory. Nonvolatile memory chips that are programmed after they are manufactured, and, if necessary, can be erased by some means and reprogrammed. Compare with EEPROM and PROM. erasable programmable read-only memory See EPROM. ESD Acronym for electrostatic discharge. A flow or spark of electricity that originates from a static source such as a carpet and arcs across a gap to another object. Ethernet Baseband LAN specification invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps. Ethernet is similar to the IEEE 802.3 series of standards. expansion card The expansion card is a printed circuit board that can be inserted into a computer to give the computer added capabilities. expansion slot The expansion slot is an opening in a computer where a circuit board can be inserted to add new capabilities to the computer. Fast Ethernet Any of a number of 100-Mbps Ethernet specifications. Fast Ethernet offers a speed increase ten times that of the 10BASE-T Ethernet specification while preserving such qualities as frame format, MAC mechanisms, and MTU. Such similarities allow the use of existing 10BASE-T applications and network management tools on Fast Ethernet networks. Based on an extension to the IEEE 802.3 specification. fast switching Cisco feature whereby a route cache is used to expedite packet switching through a router. Contrast with slow switching. FCS Acronym for frame check sequence. Refers to the extra characters added to a frame for error control purposes. Used in HDLC, Frame Relay, and other data-link layer protocols. FDDI Acronym for Fiber Distributed Data Interface. LAN standard, defined by ANSI X3T9.5, specifying a 100-Mbps token-passing network using fiber-optic cable, with transmission distances of up to 2 km. FDDI uses a dual-ring architecture to provide redundancy. Compare with CDDI and FDDI II. FDDI II ANSI standard that enhances FDDI. FDDI II provides isochronous transmission for connectionless data circuits and connection- oriented voice and video circuits. Compare with FDDI. FDM Acronym for frequency-division multiplexing. Technique whereby information from multiple channels can be allocated bandwidth on a single wire based on frequency. Compare with ATDM, statistical multiplexing, and TDM. FECN Acronym for forward explicit congestion notification. Bit set by a Frame Relay network to inform DTE receiving the frame that congestion was experienced in the path from source to destination. DTE receiving frames with the FECN bit set can request that higher-level protocols take flow-control action as appropriate. Compare with BECN. Fiber Distributed Data Interface
- 152. Study Notes http://SlideShare.net/OxfordCambridge 152| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n See FDDI. fiber-optic cable Physical medium capable of conducting modulated light transmission. Compared with other transmission media, fiber-optic cable is more expensive, but is not susceptible to electromagnetic interference, and is capable of higher data rates. Sometimes called optical fiber. File Transfer Protocol See FTP. firewall Router or access server, or several routers or access servers, designated as a buffer between any connected public networks and a private network. A firewall router uses access lists and other methods to ensure the security of the private network. firmware Software instructions set permanently or semi permanently in ROM. flash memory Technology developed by Intel and licensed to other semiconductor companies. Flash memory is nonvolatile storage that can be electrically erased and reprogrammed. Allows software images to be stored, booted, and rewritten as necessary. flash update Routing update sent asynchronously in response to a change in the network topology. Compare with routing update. flat addressing Scheme of addressing that does not use a logical hierarchy to determine location. flooding Traffic passing technique used by networking devices such as routers and switches in which traffic received on an interface is sent out all of the interfaces of that device except the interface on which the information was originally received. flow Stream of data traveling between two endpoints across a network (for example, from one LAN station to another). Multiple flows can be transmitted on a single circuit. flow control Technique for ensuring that a transmitting entity, such as a modem, does not overwhelm a receiving entity with data. When the buffers on the receiving device are full, a message is sent to the sending device to suspend the transmission until the data in the buffers has been processed. In IBM networks, this technique is called pacing. fractional T1 Access link operating at 1.544 Mbps that is subdivided into 24 channels (23 B-channels and one D-channel) of 64 Kbps each. The individual channels or groups of channels connect to different destinations. Supports DDR, Frame Relay, and X.25. Also referred to as channelized T1. fragment Piece of a larger packet that has been broken down to smaller units. frame Logical grouping of information sent as a data-link layer unit over a transmission medium. Often refers to the header and trailer, used for synchronization and error control, that surround the user data contained in the unit. The terms datagram, message, packet, and segment are also used to describe logical information groupings at various layers of the OSI reference model and in various technology circles. Frame Relay Industry-standard, switched data-link layer protocol that handles multiple virtual circuits using HDLC encapsulation between connected devices. Frame Relay is more efficient than X.25, the protocol for which it is generally considered a replacement. frequency Number of cycles, measured in hertz, of an alternating current signal per unit time. front end Node or software program that requests services of a back end. Usually is the user interface. FRU Acronym for field-replaceable unit. Hardware component that can be removed and replaced by Ciscocertified service providers. Typical FRUs include cards, power supplies, and chassis components. FTP
- 153. Study Notes http://SlideShare.net/OxfordCambridge 153| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Acronym for File Transfer Protocol. Popular network application that allows files to be moved from one network device to another. Part of the TCP/IP protocol stack, used for transferring files between network nodes. FTP is defined in RFC 959. full duplex Capability for simultaneous data transmission between a sending station and a receiving station. full mesh Term describing a network in which devices are organized in a mesh topology, with each network node having either a physical circuit or a virtual circuit connecting it to every other network node. A full mesh provides a great deal of redundancy, but because it can be prohibitively expensive to implement, it is usually reserved for network backbones. gateway In the IP community, an older term referring to a routing device. Today, the term router is used to describe nodes that perform this function, and gateway refers to a specialpurpose device that performs an application layer conversion of information from one protocol stack to another. Compare with router. GB Acronym for gigabyte. Gb Acronym for gigabit. GBps Acronym for gigabytes per second. Gbps Acronym for gigabits per second. GHz Acronym for gigahertz gigabit Abbreviated to Gb. Gigabit Ethernet An extension of the IEEE 802.3 Ethernet standard, Gigabit Ethernet increases speed tenfold over Fast Ethernet, to 1000 Mbps, or 1 gigabit per second (Gbps). Two IEEE 802.3 standards, IEEE 802.3z and IEEE 802.3ab, define Gigabit Ethernet operations over fiber- optic and twisted-pair cable. gigabits per second Abbreviated to Gbps. gigabyte Abbreviated to GB. gigabytes per second Abbreviated to GBps. gigahertz Abbreviated to GHz. gigahertz (GHz) A gigahertz is one thousand million, or 1 billion (1,000,000,000), cycles per second. graphical user interface See GUI. GUI Acronym for graphical user interface. User environment that uses pictorial as well as textual representations of the input and output of applications and the hierarchical or other data structure in which information is stored. Conventions such as buttons, icons, and windows are typical, and many actions are performed using a pointing device (such as a mouse). Microsoft Windows and the Apple Macintosh are prominent examples of platforms utilizing a GUI. half duplex Capability for data transmission in only one direction at a time between a sending station and a receiving station. Compare with full duplex and simplex. handshake Sequence of messages exchanged between two or more network devices to ensure transmission synchronization. hard disk drive
- 154. Study Notes http://SlideShare.net/OxfordCambridge 154| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n A drive device that reads and writes data on a hard disk, and is completely and internally self-contained. A hard drive allows for larger data storage capacity than floppy drives, and is non-removable. hardware address MAC address. HDLC Acronym for high-level data link control. Bit-oriented synchronous data-link layer protocol developed by ISO. Derived from SDLC, HDLC specifies a data encapsulation method on synchronous serial links using frame characters and checksums. hertz (Hz) A hertz is a unit of frequency. It is the rate of change in the state or cycle in a sound wave, alternating current, or other cyclical waveform. It represents one cycle per second and is used to describe the speed of a computer microprocessor. hexadecimal Base 16. A number representation using the digits 0 through 9, with their usual meaning, plus the letters A through F to represent hexadecimal digits with values of 10 to 15. The right-most digit counts ones, the next counts multiples of 16, then 16^2=256, etc. hierarchical routing Routing based on a hierarchical addressing system. For example, IP routing algorithms use IP addresses, which contain network numbers, subnet numbers, and host numbers. hierarchical star topology Extended star topology where a central hub is connected by vertical cabling to other hubs that are dependent on it. high-level data link control See HDLC. holddown State into which a route is placed so that routers will neither advertise the route nor accept advertisements about the route for a specific length of time (the holddown period). Holddown is used to flush bad information about a route from all routers in the network. A route is typically placed in holddown when a link in that route fails. hop Term describing the passage of a data packet between two network nodes (for example, between two routers). hop count Routing metric used to measure the distance between a source and a destination. RIP uses hop count as its sole metric. host Computer system on a network. Similar to the term node except that host usually implies a computer system, whereas node generally applies to any networked system, including access servers and routers. HTTP Acronym for Hypertext Transfer Protocol. The protocol used by Web browsers and Web servers to transfer files, such as text and graphics files. hub Generally, a term used to describe a device that serves as the center of a startopology network. 2. Hardware or software device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat, but merely split, signals sent through them). 3. In Ethernet and IEEE 802.3, an Ethernet multiport repeater, sometimes referred to as a concentrator. hypertext Electronically-stored text that allows direct access to other texts by way of encoded links. Hypertext documents can be created using HTML, and often integrate images, sound, and other media that are commonly viewed using a WWW browser. Hypertext Transfer Protocol See HTTP. Hz See hertz. ICMP Acronym for Internet Control Message Protocol. Network layer Internet protocol that reports errors and provides other information relevant to IP packet processing. Documented in RFC 792. IDF Acronym for Intermediate distribution facility. Secondary communications room for a building using a star networking topology. The IDF is dependent on the MDF.
- 155. Study Notes http://SlideShare.net/OxfordCambridge 155| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n IEEE 802.2 An IEEE LAN protocol that specifies an implementation of the LLC sublayer of the datalink layer. IEEE 802.2 handles errors, framing, flow control, and the network-layer (Layer 3) service interface. Used in IEEE 802.3 and IEEE 802.5 LANs. IEEE 802.3 An IEEE LAN protocol that specifies an implementation of the physical layer and the MAC sublayer of the data-link layer. IEEE 802.3 uses CSMA/CD access at a variety of speeds over a variety of physical media. Extensions to the IEEE 802.3 standard specify implementations for Fast Ethernet. Physical variations of the original IEEE 802.3 specification include 10BASE2, 10BASE5, 10BASE-F, 10BASE-T, and 10Broad36. Physical variations for Fast Ethernet include 100BASE-TX and 100BASE-FX. IGP Acronym for Interior Gateway Protocol. Internet protocol used to exchange routing information within an autonomous system. Examples of common Internet IGPs include IGRP, OSPF, and RIP. IGRP Acronym for Interior Gateway Routing Protocol. IGP developed by Cisco to address the problems associated with routing in large, heterogeneous networks. Compare with Enhanced IGRP. in-band signaling Transmission within a frequency range normally used for information transmission. Compare with out-of-band signaling. Industry Standard Architecture See ISA. infrared Electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum. LAN systems based on this technology represent an emerging technology. insulator Any material with a high resistance to electrical current. Integrated Services Digital Network See ISDN. Interface 1.Connection between two systems or devices. 2. In routing terminology, a network connection. 4. The boundary between adjacent layers of the <a href="#"><span class="crossref">OSI</span></a>model. internet Short for internetwork. Not to be confused with the Internet. Internet Term used to refer to the largest global internetwork, connecting tens of thousands of networks worldwide and having a "culture" that focuses on research and standardization based on real-life use. Many leading-edge network technologies come from the Internet community. The Internet evolved in part from ARPANET. At one time, called the DARPA Internet. Not to be confused with the general term internet. Internet Control Message Protocol See ICMP. internetwork Collection of networks interconnected by routers and other devices that functions (generally) as a single network. Sometimes called an internet, which is not to be confused with the Internet. Internetwork Packet Exchange See IPX. internetworking General term used to refer to the industry that has arisen around the problem of connecting networks together. The term can refer to products, procedures, and technologies. IPX Acronym for Internetwork Packet Exchange. NetWare network layer (Layer 3) protocol used for transferring data from servers to workstations. IPX is similar to IP and XNS. ISA Acronym for Industry Standard Architecture. An older standard for connecting peripherals to a personal computer. Used primarily in AT-style IBM compatibles.
- 156. Study Notes http://SlideShare.net/OxfordCambridge 156| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n ISDN Acronym for Integrated Services Digital Network. Communication protocol, offered by telephone companies, that permits telephone networks to carry data, voice, and other source traffic. IS-IS Acronym for Intermediate System-to-Intermediate System. OSI link-state hierarchical routing protocol based on DECnet Phase V routing whereby ISs (routers) exchange routing information based on a single metric to determine network topology. Compare with Integrated IS-IS. jabber Error condition in which a network device continually transmits random, meaningless data onto the network. 2. In IEEE 802.3, a data packet whose length exceeds that prescribed in the standard. jitter Analog communication line distortion caused by the variation of a signal from its reference timing positions. Jitter can cause data loss, particularly at high speeds. jumper Term used for patchcords found in a wiring closet. 2.)Electrical switch consisting of a number of pins and a connector that can be attached to the pins in a variety of different ways. Different circuits are created by attaching the connector to different pins. KB Acronym for kilobyte. Approximately 1000 bytes. Kb Acronym for kilobit. Approximately 1000 bits. kBps Acronym for kilobytes per second. kbps Acronym for kilobits per second. keepalive interval Period of time between each keepalive message sent by a network device. keepalive message Message sent by one network device to inform another network device that the virtual circuit between the two is still active. kilobit Abbreviated to kb. kilobits per second Abbreviated to kbps. This is a standard measurement of the amount of data transferred over a network connection. kilobyte Abbreviated to KB. kilobytes per second Abbreviated to kBps. This is a standard measurement of the amount of data transferred over a network connection. LAN Acronym for local-area network. High-speed, low-error data network covering a relatively small geographic area (up to a few thousand meters). LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area. LAN standards specify cabling and signaling at the physical and data-link layers of the OSI model. Ethernet, FDDI, and Token Ring are widely used LAN technologies. LAN switch High-speed switch that forwards packets between data-link segments. Most LAN switches forward traffic based on MAC addresses. This variety of LAN switch is sometimes called a frame switch. LAN switches are often categorized according to the method they use to forward traffic: cut-through packet switching or store-and-forward packet switching. Multilayer switches are an intelligent subset of LAN switches. An example of a LAN switch is the Cisco Catalyst 5000. Compare with multilayer switch. LAPB Acronym for Link Access Procedure Balanced. Data-link layer protocol in the X.25 protocol stack. LAPB is a bit-oriented protocol derived from HDLC. LAPD
- 157. Study Notes http://SlideShare.net/OxfordCambridge 157| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Acronym for Link Access rocedure on the D channel. ISDN data-link layer protocol for the D channel. LAPD was derived from the LAPB protocol and is designed primarily to satisfy the signaling requirements of ISDN basic access. Defined by ITU-T Recommendations Q.920 and Q.921. laser Light amplification by stimulated emission of radiation. Analog transmission device in which a suitable active material is excited by an external stimulus to produce a narrow beam of coherent light that can be modulated into pulses to carry data. Networks based on laser technology are sometimes run over SONET. latency Delay between the time a device requests access to a network and the time it is granted permission to transmit. 2. Delay between the time when a device receives a frame and the time that frame is forwarded out the destination port. leased line Transmission line reserved by a communications carrier for the private use of a customer. A leased line is a type of dedicated line. LED Acronym for light emitting diode. Semiconductor device that emits light produced by converting electrical energy. Status lights on hardware devices are typically LEDs. line of sight Characteristic of certain transmission systems such as laser, microwave, and infrared systems in which no obstructions in a direct path between transmitter and receiver can exist. link Network communications channel consisting of a circuit or transmission path and all related equipment between a sender and a receiver. Most often used to refer to a WAN connection. Sometimes referred to as a line or a transmission link. link-state routing algorithm Routing algorithm in which each router broadcasts or multicasts information regarding the cost of reaching each of its neighbors to all nodes in the internetwork. Link-state algorithms create a consistent view of the network and are therefore not prone to routing loops, but they achieve this at the cost of relatively greater computational difficulty and more widespread traffic (compared with distance vector routing algorithms). Compare with distance vector routing algorithm. LLC Acronym for Logical Link Control. Higher of the two data-link layer sublayers defined by the IEEE. The LLC sublayer handles error control, flow control, framing, and MAC-sublayer addressing. The most prevalent LLC protocol is IEEE 802.2, which includes both connectionless and connection-oriented variants. local loop loop Line from the premises of a telephone subscriber to the telephone company CO. Route where packets never reach their destination, but simply cycle repeatedly through a constant series of network nodes. loopback test Test in which signals are sent and then directed back toward their source from some point along the communications path. Loopback tests are often used to test network interface usability. MAC Acronym for Media Access Control. Lower of the two sublayers of the data-link layer defined by the IEEE. The MAC sublayer handles access to shared media, such as whether token passing or contention will be used. MAC address Standardized data-link layer address that is required for every port or device that connects to a LAN. MAC addresses are six bytes long and are controlled by the IEEE. Also known as a hardware address, MAC layer address, and physical address. main distribution facility See MDF. MAN Acronym for metropolitan-area network. Network that spans a metropolitan area. Generally, a MAN spans a larger geographic area than a LAN, but a smaller geographic area than a WAN. MDF Acronym for main distribution facility. Primary communications room for a building. Central point of a star networking topology where patch panels, hub, and router are located. Media Access Control See MAC. megabit (Mb)
- 158. Study Notes http://SlideShare.net/OxfordCambridge 158| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n A megabit is approximately 1 million bits. megabits per second (Mbps) A standard measurement of the amount of data transferred over a network connection during a time period of one second. megabyte (MB) A megabyte is approximately 1 million bytes (1,048,576 bytes exactly). A megabyte is sometimes referred to as a "meg." megabytes per second(MBps) A standard measurement of the amount of data transferred over a network connection during a time period of one second. megahertz (MHz) A megahertz is one million cycles per second. This is a common measurement of the speed of a processing chip, such as a computer microprocessor. metropolitan-area network See MAN. microprocessor A microprocessor is a silicon chip that contains a CPU. modulation Process by which the characteristics of electrical signals are transformed to represent information. Modems perform modulation by taking a digital signal and altering it to an analog signal. mouse port This port is designed for connecting a mouse to a PC. multicast Single packets copied by the network and sent to a specific subset of network addresses. These addresses are specified in the destination address field. See broadcast. multicast address Single address that refers to multiple network devices in a group. Synonymous with group address. multiplexing Scheme that allows multiple logical signals to be transmitted simultaneously across a single physical channel. NAK Acronym for negative acknowledgment. Response sent from a receiving device to a sending device indicating that the information received contained errors. narrowband See baseband. negative acknowledgment See NAK. network Collection of computers, printers, routers, switches, and other devices that are able to communicate with each other over some transmission medium. 2. Command that assigns a NIC-based address to which the router is directly connected. 3. Command that specifies any directly connected networks to be included. network card The network card is an expansion board inserted into a computer so that the computer can be connected to a network. network interface card See NIC. network layer Layer 3 of the OSI reference model. This layer provides connectivity and path selection between two end systems. The network layer is the layer at which routing occurs. Corresponds roughly with the path control layer of the SNA model. NIC Acronym for network interface card. Board that provides network communication capabilities to and from a computer system. Also called an adapter. nonvolatile RAM See NVRAM. NVRAM
- 159. Study Notes http://SlideShare.net/OxfordCambridge 159| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Acronym for nonvolatile RAM. RAM that retains its contents when a unit is powered off. OIR Acronym for online insertion and removal. Feature that permits the addition, the replacement, or the removal of cards without interrupting the system power, entering console commands, or causing other software or interfaces to shut down. Sometimes called hot swapping or power-on servicing. OSI Acronym for Open System Interconnection. International standardization program created by ISO and ITU-T to develop standards for data networking that facilitate multivendor equipment interoperability. out-of-band signaling Transmission using frequencies or channels outside the frequencies or channels normally used for information transfer. Out-of- band signaling is often used for error reporting in situations in which in-band signaling can be affected by whatever problems the network might be experiencing. Contrast with in-band signaling. packet Logical grouping of information at Layer 3 that includes a header containing control information and a PDU from the same or upper layer. Packets are used to refer to network layer units of data. The terms datagram, frame, message, and segment are also used to describe logical information groupings at various layers of the OSI reference model and in various technology circles. PAP Acronym for Password Authentication Protocol. Authentication protocol that allows PPP peers to authenticate one another. The remote router attempting to connect to the local router is required to send an authentication request. Unlike CHAP, PAP passes the password and host name or username in the clear (unencrypted). PAP does not itself prevent unauthorized access, but merely identifies the remote end. The router or access server then determines if that user is allowed access. PAP is supported only on PPP lines. parallel port The parallel port is an interface capable of transferring more than one bit simultaneously through a single cable containing multiple conductors. It is used to connect external devices, such as printers and internal devices to hard drives. Password Authentication Protocol See PAP. patch panel An assembly of pin locations and ports that can be mounted on a rack or wall bracket in the wiring closet. Patch panels act like switchboards that connect workstation cables to each other and to the outside. path cost See cost. PCB Acronym for printed circuit board. The PCB is a thin plate on which chips (integrated circuits) and other electronic components are placed. PCI Acronym for peripheral component interconnect. A standard for connecting peripherals to a personal computer. Used primarily in Pentium- and AMD-based systems, it is processor independent, therefore can work with other processor architectures. PCMCIA Acronym for Personal Computer Memory Card International Association. PCMCIA is an organization that has developed a standard for small, credit-card sized devices, called PC cards. Originally designed for adding memory to portable computers, the PCMCIA standard has been expanded several times and is now suitable for many types of devices. PDU Acronym for protocol data unit. OSI term for a layer-specific grouping of data. peripheral component interconnect See PCI. Personal Computer Memory Card International Association See PCMCIA. physical layer Layer 1 of the OSI reference model. The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems. Corresponds with the physical control layer in the SNA model. ping
- 160. Study Notes http://SlideShare.net/OxfordCambridge 160| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Acronym for packet internet groper. ICMP echo message and its reply. Often used in IP networks to test the reachability of a network device. power cord The power cord is used to connect an electrical device to an electrical outlet in order to provide power to the device. presentation layer Layer 6 of the OSI reference model. This layer ensures that information sent by the application layer of one system will be readable by the application layer of another. The presentation layer is also concerned with the data structures used by programs and therefore negotiates data transfer syntax for the application layer. PRI Acronym for Primary Rate Interface. ISDN interface to primary rate access. Primary rate access consists of a single 64-Kbps D channel plus 23 (T1) or 30 (E1) B channels for voice or data. Primary Rate Interface See PRI. printed circuit board See PCB. process A single thread of computation to achieve a specific goal performed within a microprocessor or software. PROM Acronym for programmable read-only memory. ROM that can be programmed using special equipment. PROMs can be programmed only once. Compare with EPROM. propagation delay Time required for data to travel over a network, from its source to its ultimate destination. protocol Formal description of a set of rules and conventions that govern how devices on a network exchange information. protocol data unit See PDU. QoS Acronym for quality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability. QoS parameters Acronym for quality of service parameters. Parameters that control the amount, performance, and reliability of traffic on a transmission device on a network. query Message used to inquire about the value of some variable or set of variables. queue Generally, an ordered list of elements waiting to be processed. 2. In routing, a backlog of packets waiting to be forwarded over a router interface. queuing delay Amount of time that data must wait before it can be transmitted onto a statistically multiplexed physical circuit. RAM Acronym for random-access memory. Also known as read-write memory, RAM can have new data written into it as well as stored data read from it. If the computer is turned off or loses power, all data stored in RAM is lost unless the data was previously saved to disk. random-access memory See RAM. RARP Acronym for Reverse Address Resolution Protocol. Protocol in the TCP/IP stack that provides a method for acquiring an IP address based on MAC addresses. Reverse Address Resolution Protocol See RARP. ring topology
- 161. Study Notes http://SlideShare.net/OxfordCambridge 161| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Network topology that consists of a series of repeaters connected to one another by unidirectional transmission links to form a single closed loop. Each station on the network connects to the network at a repeater. While logically a ring, ring topologies are most often organized in a closed-loop star. RIP Acronym for Routing Information Protocol. IGP supplied on many UNIX systems. The most common IGP in the Internet. RIP uses hop count as a routing metric. RJ connector Acronym for registered jack connector. Standard connectors originally used to connect telephone lines. RJ connectors are now used for telephone connections and for 10BASE-T and other types of network connections. RJ-11, RJ-12, and RJ-45 are popular types of RJ connectors. ROM Acronym for read-only memory. ROM is computer memory on which data has been prerecorded. ROM Acronym for read-only memory. Nonvolatile memory that can be read, but not written, by the microprocessor. route Path through an internetwork. routed protocol Protocol that can be routed by a router. A router must be able to interpret the logical internetwork as specified by that routed protocol. Examples of routed protocols include AppleTalk, DECnet, and IP. router Network layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information. Generally called a gateway when used by a device to forward traffic off a local network and that does not participate in routing or multiple networks. routing Process of finding a path to a destination host. Routing is very complex in large networks because of the many potential intermediate destinations a packet might traverse before reaching its destination host. Routing Information Protocol See RIP. routing metric Method by which a routing algorithm determines that one route is better than another. This information is stored in routing tables. Metrics include bandwidth, communication cost, delay, hop count, load, MTU, path cost, and reliability. Sometimes referred to simply as a metric. routing protocol Protocol that accomplishes routing through the implementation of a specific routing algorithm. Examples of routing protocols include IGRP, OSPF, and RIP. routing table Table stored in a router or some other internetworking device that keeps track of routes to particular network destinations and, in some cases, metrics associated with those routes. RS-232 Popular physical-layer interface. Now known as EIA/TIA-232. RS-422 Balanced electrical implementation of EIA/TIA-449 for high-speed data transmission. Now referred to collectively with RS-423 as EIA-530. RS-423 Unbalanced electrical implementation of EIA/TIA-449 for EIA/TIA-232 compatibility. Now referred to collectively with RS-422 as EIA-530. RS-449 Popular physical-layer interface. Now known as EIA/TIA-449. SAN Acronym for storage area network. An emerging data communications platform that interconnects servers and storage at gigabaud speeds. By combining LAN networking models with the core building blocks off server performance and mass storage capacity, SAN eliminates the bandwidth bottlenecks and scalability limitations imposed by previous SCSI busbased architectures.
- 162. Study Notes http://SlideShare.net/OxfordCambridge 162| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n SDLC Acronym for Synchronous Data Link Control. SNA data-link layer communications protocol. SDLC is a bit-oriented, full-duplex serial protocol that has spawned numerous similar protocols, including HDLC and LAPB. serial port This interface can be used for serial communication in which only one bit is transmitted at a time. server Node or software program that provides services to clients. session layer Layer 5 of the OSI reference model. This layer establishes, manages, and terminates sessions between applications and manages data exchange between presentation layer entities. Corresponds to the data-flow control layer of the SNA model. Simple Network Management Protocol See SNMP. slow switching Packet processing performed at process level speeds, without the use of a route cache. Contrast with fast switching. SNMP Acronym for Simple Network Management Protocol. Network management protocol used almost exclusively in TCP/IP networks. SNMP provides a means to monitor and control network devices, and to manage configurations, statistics collection, performance, and security. sound card A sound card is an expansion board that handles all sound functions. SRAM Type of RAM that retains its contents for as long as power is supplied. SRAM does not require constant refreshing, like DRAM. Compare with DRAM. star topology LAN topology in which end points on a network are connected to a common central switch by point-to-point links. A ring topology that is organized as a star implements a unidirectional closed-loop star, instead of point-to-point links. statistical multiplexing Technique whereby information from multiple logical channels can be transmitted across a single physical channel. Statistical multiplexing dynamically allocates bandwidth only to active input channels, making better use of available bandwidth and allowing more devices to be connected than with other multiplexing techniques. Also referred to as statistical time-division multiplexing or stat mux. storage area network See SAN. STP Acronym for shielded twisted-pair. See UTP. Synchronous Data Link Control See SDLC. synchronous transmission Term describing digital signals that are transmitted with precise clocking. Such signals have the same frequency, with individual characters encapsulated in control bits (called start bits and stop bits) that designate the beginning and end of each character. T1 Digital WAN carrier facility. T1 transmits DS-1-formatted data at 1.544 Mbps through the telephone-switching network, using AMI or B8ZS coding. TDM Acronym for time-division multiplexing. Technique in which information from multiple channels can be allocated bandwidth on a single wire based on preassigned time slots. Bandwidth is allocated to each channel regardless of whether the station has data to transmit. See FDM. terminal Simple device at which data can be entered or retrieved from a network or device. Generally, terminals have a monitor and a keyboard, but no processor or local disk drive. TFTP
- 163. Study Notes http://SlideShare.net/OxfordCambridge 163| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Acronym for Trivial File Transfer Protocol. Simplified version of FTP that allows files to be transferred from one computer to another over a network, usually without the use of client authentication (for example, username and password). time-division multiplexing See TDM. token passing Network media access method by which network devices access the physical medium in an orderly fashion based on possession of a small frame called a token. Contrast with circuit switching and contention. Token Ring An IEEE 802 LAN that makes use of token passing on a physical or logical ring topology. transport layer Layer 4 of the OSI reference model. This layer is responsible for reliable network communication between end nodes. The transport layer provides mechanisms for the establishment, maintenance, and termination of virtual circuits, transport fault detection and recovery, and information flow control. Corresponds to the transmission control layer of the SNA model. UART Universal Asynchronous Receiver/Transmitter. Integrated circuit, attached to the parallel bus of a computer, used for serial communications. The UART translates between serial and parallel signals, provides transmission clocking, and buffers data sent to or from the computer. UBR Acronym for unspecified bit rate. QoS class defined by the ATM Forum for ATM networks. UBR allows any amount of data up to a specified maximum to be sent across the network, but there are no guarantees in terms of cell loss rate and delay. Compare with ABR (available bit rate), CBR, and VBR. UDP Acronym for User Datagram Protocol. Connectionless transport layer protocol in the TCP/IP protocol stack. UDP is a simple protocol that exchanges datagrams without acknowledgments or guaranteed delivery, requiring that error processing and retransmission be handled by other protocols. UDP is defined in RFC 768. UL Acronym for Underwriters Laboratories. Independent agency within the United States that tests product safety. unicast Message sent to a single network destination. Compare with broadcast and multicast. unicast address Address specifying a single network device. UPS Acronym for uninterruptible power supply. Backup device designed to provide an uninterrupted power source in the event of a power failure. They are commonly installed on all file servers and wiring hubs. User Datagram Protocol See UDP. UTP Acronym for unshielded twisted-pair. Four-pair wire medium used in a variety of networks. UTP does not require the fixed spacing between connections that is necessary with coaxial-type connections. There are five types of UTP cabling commonly used: Category 1 cabling, Category 2 cabling, Category 3 cabling, Category 4 cabling, and Category 5 cabling. Compare with STP. V.32 ITU-T standard serial-line protocol for bidirectional data transmissions at speeds of 4.8 or 9.6 kbps. V.34 ITU-T standard that specifies a serial line protocol. V.34 offers improvements to the V.32 standard, including higher transmission rates (28.8 kbps) and enhanced data compression. Compare with V.32. V.35 ITU-T standard describing a synchronous, physical-layer protocol used for communications between a network access device and a packet network. V.35 is most commonly used in the United States and in Europe, and is recommended for speeds up to 48 kbps. VBR Acronym for variable bit rate. QoS class defined by the ATM Forum for ATM networks. VBR is subdivided into a real time (RT) class and non-real time (NRT) class. VBR (RT) is used for connections in which there is a fixed timing relationship between samples. VBR (NRT) is used for connections in which there is no fixed timing relationship between samples, but that still need a guaranteed QoS. See UBR.
- 164. Study Notes http://SlideShare.net/OxfordCambridge 164| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n vertical cabling Backbone cabling. virtual circuit Logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI/VCI pair, and can be either permanent (a PVC) or switched (an SVC). Virtual circuits are used in Frame Relay and X.25. In ATM, a virtual circuit is called a virtual channel. Sometimes abbreviated VC. virtual terminal Software driven terminal emulation to provide the same functionality of a local terminal or console to a remote location or device. VLAN Acronym for virtual LAN. Group of devices on a LAN that are configured so that they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLANs are based on logical instead of physical connections, they are extremely flexible. VPN Acronym for Virtual Private Network. A logical network created through the use of encapsulation or tagging techniques. WAN Acronym for wide-area network. Data communications network that serves users across a broad geographic area and often uses transmission devices provided by common carriers. Frame Relay, SMDS, and X.25 are examples of WANs. wideband See broadband. wildcard mask 32-bit quantity used in conjunction with an IP address to determine which bits in an IP address should be ignored when comparing that address with another IP address. A wildcard mask is specified when setting up access lists. window Number of octets that the receiver is willing to accept. window size Refers to the number of messages that can be transmitted while awaiting an acknowledgment. wire map Feature provided by most cable testers. Used to test twisted-pair cable installations, it shows which wire pairs connect to which pins on the plugs and sockets. wiring closet Specially designed room used for wiring a data or voice network. Wiring closets serve as a central junction point for the wiring and wiring equipment that is used for interconnecting devices. workgroup Collection of workstations and servers on a LAN that are designed to communicate and exchange data with one another. workgroup switching Method of switching that provides high-speed (100-Mbps) transparent bridging between Ethernet networks and high-speed translational bridging between Ethernet and CDDI or FDDI. X terminal Terminal that allows a user simultaneous access to several different applications and resources in a multivendor environment through implementation of X Windows. X Windows Distributed, network-transparent, device-independent, multitasking windowing and graphics system originally developed by MIT for communication between X terminals and UNIX workstations. X.25 ITU-T standard that defines how connections between DTE and DCE are maintained for remote terminal access and computer communications in PDNs. X.25 specifies LAPB, a data-link layer protocol, and PLP, a network-layer protocol. Frame Relay has to some degree superseded X.25. 10 Mbps Approximately 10 million bits per second, an information transfer rate. 100BASE-FX 100-Mbps baseband Fast Ethernet specification using two strands of multimode fiberoptic cable per link. To guarantee proper signal timing, a 100BASE-FX link cannot exceed 1312 feet (400 meters) in length. Based on the IEEE 802.3 standard.
- 165. Study Notes http://SlideShare.net/OxfordCambridge 165| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n 100BASE-T 100-Mbps baseband Fast Ethernet specification using UTP wiring. Like the 10BASE-T technology on which it is based, 100BASE-T sends link pulses over the network segment when no traffic is present. However, these link pulses contain more information than those used in 10BASE-T. Based on the IEEE 802.3 standard. 100BASE-T4 100-Mbps baseband Fast Ethernet specification using four pairs of Category 3, 4, or 5 UTP wiring. To guarantee proper signal timing, a 100BASE-T4 segment cannot exceed 328 feet (100 meters) in length. Based on the IEEE 802.3 standard. 100BASE-TX 100-Mbps baseband Fast Ethernet specification using two pairs of either UTP or STP wiring. The first pair of wires is used to receive data; the second is used to transmit. To guarantee proper signal timing, a 100BASE-TX segment cannot exceed 328 feet (100 meters) in length. Based on the IEEE 802.3 standard. 100BASE-X 100-Mbps baseband Fast Ethernet specification that refers to the 100BASE-FX and 100BASE-TX standards for Fast Ethernet. Based on the IEEE 802.3 standard. 10BASE2 10-Mbps baseband Ethernet specification using 50-ohm thin coaxial cable. 10BASE2, which is part of the IEEE 802.3 specification, has a distance limit of 185 meters per segment. 10BASE5 10-Mbps baseband Ethernet specification using standard (thick) 50-ohm baseband coaxial cable. 10BASE5, which is part of the IEEE 802.3 baseband physical layer specification, has a distance limit of 500 meters per segment. 10BASE-F 10-Mbps baseband Ethernet specification that refers to the 10BASE-FB, 10BASE-FL, and 10BASE-FP standards for Ethernet over fiber-optic cabling. 10BASE-FB 10-Mbps baseband Ethernet specification using fiber-optic cabling. 10BASE-FB is part of the IEEE 10BASE-F specification. It is not used to connect user stations, but instead provides a synchronous signaling backbone that allows additional segments and repeaters to be connected to the network. 10BASE-FB segments can be up to 2000 meters long. 10BASE-FL 10-Mbps baseband Ethernet specification using fiber-optic cabling. 10BASE-FL is part of the IEEE 10BASE-F specification and, while able to interoperate with FOIRL, is designed to replace the FOIRL specification. 10BASE-FL segments can be up to 1000 meters long if used with FOIRL, and up to 2000 meters if 10BASE-FL is used exclusively. 10BASE-FP 10-Mbps fiber-passive baseband Ethernet specification using fiber-optic cabling. 10BASE-FP is part of the IEEE 10BASE-F specification. It organizes a number of computers into a star topology without the use of repeaters. 10BASE-FP segments can be up to 500 meters long. 10BASE-T 10-Mbps baseband Ethernet specification using two pairs of twisted-pair cabling (Category 3, 4, or 5): one pair for transmitting data and the other for receiving data. 10BASE-T, which is part of the IEEE 802.3 specification, has a distance limit of approximately 328 feet (100 meters) per segment.
- 166. Study Notes http://SlideShare.net/OxfordCambridge 166| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n N. Answers to Quizzes i Answer A server is a powerful computer that provides resources to other computers on the network, a workstation is any computer on a network that can request resources and is used to do work, and a host is any network device that has a TCP/IP address. Each host has a unique IP address on the network. Servers can be set to perform only one dedicated task. Workstations are faster and of a higher specification than personal computers. ii Answer The client/server network model has centralized management, good security, and is scalable. Option 1 is correct. A client/server network is managed from a central point, which is the server. Option 2 is incorrect. In the client/server network model, the clients cannot act as servers. They rely on servers for their resources. Option 3 is correct. A client/server network has all username and password details securely stored on a server. This information is not available to the users on the network. Option 4 is correct. The size of a client/server network is virtually unlimited. It can be continually grown by adding new clients and servers. iii Answer When compared with a peer-to-peer network, a client/server network is more efficient, more secure, and easier to manage. Option 1 is incorrect. Access rights are handled by clients in a peer-to-peer network. In a client/server network, the server is responsible for holding the resources and granting access to them. Option 2 is correct. A client/server network is easier to manage, because it is managed from a central location. Option 3 is correct. A client/server network is more efficient because all the files are stored centrally on servers, making them easier to locate and access. Option 4 is correct. Client/server networks offer greater security, because all the passwords and usernames are stored on a server and are hidden from users on the network.
- 167. Study Notes http://SlideShare.net/OxfordCambridge 167| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n iv Answer A LAN is limited to a specific area. Option 1 is correct. LANs are designed to link network devices over a small geographic area. Option 2 is incorrect. Wide area networks, or WANs, are used to create networks over large geographic areas. Option 3 is incorrect. LANs can also be peer-to-peer networks. Option 4 is incorrect. LANs can be scaled in size by adding additional workstations, servers, and peripheral devices to the network. v Answer WANs cover large geographic areas, and WAN connections are more expensive than LAN connections. Option 1 is correct. LANs are limited to specific areas, such as buildings. Option 2 is incorrect. WANs do connect cities together but they can also connect countries and continents together. Option 3 is correct. WAN connections are more expensive than LAN connections because ISP services are very expensive. Option 4 is incorrect. LANs primarily use private network transports while WANs can use public or private network transports. vi Answer Routers direct traffic on a network to the correct destination, WAN switches connect routers on a WAN, and modems provide remote access to a network. Modems convert digital signals to analog ones so that they can be transmitted over telephone lines. A router is connected to at least two networks, and it is located where the networks connect. WAN switches are used to logically connect routers on the WAN using virtual circuits. vii Answer A MAN is a network that spans a metropolitan area such as a city or suburban area. Option 1 is incorrect. A LAN connects workstations, peripherals, terminals, and other devices in a single building. Option 2 is incorrect. A WAN uses routers and other network devices to form a single logical network out of many networks.
- 168. Study Notes http://SlideShare.net/OxfordCambridge 168| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Option 3 is incorrect. A WAN is a network that serves users across a broad geographic area and often uses transmission devices provided by common carriers. Option 4 is correct. A MAN usually consists of two or more LANs and offers high-speed connections. viii Answer An extranet is available to users outside the business, and it requires security. Option 1 is correct. An extranet allows customers, suppliers, or other businesses to access a company's internal network. Option 2 is incorrect. An extranet is a network that is available to users outside the business. Option 3 is correct. An extranet requires a firewall to ensure that the communication is kept secure and that access to the internal network is reserved solely for those with access rights. ix Answer A LAN is confined to a small area, a WAN covers a large geographic area, and a MAN covers a city or suburban area. LANs are normally confined to buildings. They connect workstations, servers, and peripheral devices, such as printers, together. A MAN consists of several LANs connected together. A WAN can extend between countries and across continents. The Internet is an example of a global WAN. x Answer The OSI model facilitates compatibility between different networks, it explains how information travels through networks and defines the network functions that occur at each layer. Option 1 is correct. The OSI model outlines a set of network communication standards, which enables network compatibility. Option 2 is correct. The OSI model specifies the process by which data should be transmitted - this standardizes the way data travels over a network. Option 3 is incorrect. The OSI model was developed to resolve the problem of incompatible network communication. Option 4 is correct. The OSI model makes it easier for vendors to educate customers on how data is transmitted throughout a network.
- 169. Study Notes http://SlideShare.net/OxfordCambridge 169| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n xi Answer The application layer provides network services to applications, the presentation layer formats and structures data, and the session layer synchronizes and maintains communication between hosts. The transport layer ensures reliable data transfer between hosts while the network layer ensures data delivery and the data-link layer provides access to the network media. The application layer deals with file, print and messaging services. The data-link layer outlines how data is formatted and how network access is controlled. The network layer selects the most appropriate path for sending data, and routes data packets. The presentation layer ensures data is readable between hosts and also organizes the syntax of data transferred to the application layer. The session layer deals with the authentication, creation, management, and termination of sessions between different applications. The transport layer ensures complete data transfer and that data is received error-free. xii Answer Option Description D Presentation: The presentation layer ensures that the data transmitted between hosts is readable. This layer also manages data representation. E Session: The session layer synchronizes and maintains communication between hosts. F Transport: The transport layer ensures data communications are received error-free. B Network: The network layer ensures data delivery by providing connectivity and path selection between two host systems. A Data-link: The main function of the data-link layer is to provide access to the network media. C Physical: The physical layer outlines the functional, procedural, electrical, and mechanical specifications for controlling physical links.
- 170. Study Notes http://SlideShare.net/OxfordCambridge 170| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n xiii Answer The main similarities between the TCP/IP stack and the OSI model are that both models have an application layer, they both deal with packet-switched technology, and they have similar transport and network layer functions. Option 1 is correct. Each model has an application layer but their functions are slightly different. Option 2 is incorrect. The Internet layer is only found in the TCP/IP stack. Option 3 is correct. Both models assume that packet-switched, rather than circuit-switched technology, is being used. Option 4 is correct. The functions of the transport and network layers are comparable in each model. xiv Answer The transport layer deals with reliability, flow control, and error correction. Option 1 is incorrect. The application layer manages high-level protocols and ensures that application-related data is properly packaged for the layer below. Option 2 is incorrect. The Internet layer is responsible for the delivery of source packets from any network on the internetwork. Option 3 is incorrect. The network access layer handles the details in the OSI physical and data-link layers. Option 4 is correct. The transport layer provides for reliable network communications, ensuring the reliability of transmitted data. xv Answer The backplane allows external devices to be connected while the bus connects internal components to the CPU. Most computer calculations take place in the CPU. Additional cards can be plugged into the motherboard using an expansion slot. The CD-ROM drive can read and write to compact discs. The backplane allows external devices to be connected. It contains components such as a power cord, a serial port, a mouse port, and a parallel port. The bus connects internal components to the CPU. Data and control information is transmitted through the computer via its collection of wires. The CPU is the computer's "brain". It contains a silicon-based microprocessor that performs calculations. Extra functionality can be added to the computer by plugging in the appropriate card into an expansion slot. Some CD-ROM drives can both read and write to CDs.
- 171. Study Notes http://SlideShare.net/OxfordCambridge 171| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n xvi Answer Before you install a NIC, you must know how to configure the network card, how to use the network card diagnostics, and how to resolve hardware resource conflicts. Option 1 is correct. You need to know how the network card is configured. You should use the vendor-supplied diagnostics and loopback test. Option 2 is incorrect. You don't need to be familiar with all types of network cards. Some have specialized functions in networks and are not commonly used, or require specific technical expertise. Option 3 is correct. You must be able to resolve hardware resource conflicts with IRQs and DMA. Option 4 is correct. You need to know how to use the network card diagnostics by using jumpers, plug-and-play software, and EPROM. xvii Answer Before installing a NIC, you need to take into account the type of cable, network, and expansion slot on your computer. Option 1 is correct. Your network implementation will determine the cables and connectors used to connect to it. Option 2 is correct. Different networks are compatible with different NIC cards. For example, an Ethernet LAN requires an Ethernet NIC. Option 3 is incorrect. The type of CPU in your computer has no bearing on your choice of NIC. Option 4 is correct. Some computers, such as older computers, do not have the standard Peripheral Component Interconnect (PCI) slots. xviii Answer A hub regenerates network signals at bit level. It receives on one port and transmits on all other ports. Hubs are used as network concentration points. Option 1 is correct. A hub forwards network signals at the bit level. Option 2 is incorrect. A hub receives on one port and transmits on all other ports. Option 3 is correct. Hubs create a central connection point for network cables and increase the reliability of the network, because the failure of any single cable will not disrupt the entire network. Option 4 is incorrect. Hubs do not perform path determination or filtering and only port-switching or intelligent hubs are capable of switching. Any signal on any port is retransmitted to all the other ports.
- 172. Study Notes http://SlideShare.net/OxfordCambridge 172| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n xix Answer The advantages of using a bridge are that it allows more than one device to transmit simultaneously, it keeps track of which MAC addresses are on each side of the bridge, and it can rapidly forward data. Option 1 is correct. By creating multiple collision domains, bridges allow more than one device to transmit simultaneously without causing a collision. Option 2 is correct. Because bridges are layer 2 devices, they are not concerned with the network layer protocol, which means they can rapidly forward data. Option 3 is incorrect. A bridge must process all data received as its purpose is to ensure data only gets passed to the required segments of the network. Option 4 is correct. By keeping track of which MAC addresses are on each side of the bridge, bridges will only send data to specific segments, thereby significantly reducing the amount of unnecessary traffic. xx Answer A router establishes the destination network by examining the destination IP address of the packet. Option 1 is correct. A router uses IP addresses instead of MAC addresses to select the most efficient path for packet delivery. Option 2 is incorrect. A bridge uses MAC addresses to establish whether the destination of a packet is on the same segment or a different segment to that of the sender. Option 3 is incorrect. Multilayer switches use layer 3 network addresses as well as using layer 2 MAC addresses to establish the destination network for data. xxi Answer A gateway is best described as a combination of hardware and software used to connect dissimilar network environments. Option 1 is incorrect. E-mail programs use gateways to translate LAN-based mail messages into the SMTP format. Option 2 is correct. A gateway can connect, for example, an Ethernet LAN environment to an IBM mainframe environment. Option 3 is incorrect. In fact, a gateway performs translations at several layers of the OSI model. xxii Answer Bridges are layer 2 devices that create separate collision domains on each port. Routers use layer 3 addresses to transmit data packets between networks. Repeaters regenerate and retransmit network signals at layer 1 of the OSI model.
- 173. Study Notes http://SlideShare.net/OxfordCambridge 173| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Bridges also provide extra bandwidth by filtering local LAN traffic and maintaining connectivity on the segments directly linked to it. Repeaters are considered layer 1 devices because they operate at bit level. Routers employ IP addresses instead of MAC addresses to decide on the optimum path for data delivery. xxiii Answer Networks can have a physical and a logical topology. The physical topology defines the way in which network devices are connected together. Option 1 is incorrect. The logical topology of a network refers to the logical paths taken by a signal when it is passed between devices. Option 2 is incorrect. The physical topology of a network refers to the physical layout of the devices on the network. Option 3 is correct. Networks have both a logical and physical topology. The logical topology may or may not correspond to the physical topology. Option 4 is correct. The physical topology of a network describes the physical layout of the wire and devices. xxiv Answer When the cable between a network host and the central device fails on a star topology, only the host at the end of the cable becomes disconnected. Option 1 is incorrect. The problem host is affected, but the rest of the network remains operational. Option 2 is correct. The benefits gained by having each host connected to the central device with its own wire is the reason why almost every newly designed Ethernet LAN has a star topology. Option 3 is incorrect. The network does not need to reset itself because only the problem host is affected. Option 4 is incorrect. The fact that only the affected host is disconnected prevents the whole network from being disrupted. xxv Answer A bus topology requires a terminator device to function properly. On a ring topology, hosts attach data and a destination address to the passing token. On a star topology, each host is connected to the central connection device by its own cable. A bus topology experiences packet collisions unless it is equipped with a terminator device at the end of the cable. Data is transmitted around the ring by a token that stops at each network host. If the host wants to send data, it adds it to the token along with the destination address of the data.
- 174. Study Notes http://SlideShare.net/OxfordCambridge 174| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n If a problem occurs between one host and the central device, it is confined to that cable section only. xxvi Answer Category 3 cable can transmit data at 10 Mbps, category 5 cable can transmit data at 100 Mbps, and category 5e cable can transmit data at 1 Gbps. Category 3 cable is commonly used on older Ethernet networks. Category 5 cable is commonly used for Ethernet cabling to the desktop. Category 5e cable is comparatively expensive, but is the best choice for Gigabit Ethernet. xxvii Answer Coaxial cable can run for longer distances than either STP or UTP cable, and Thicknet was once commonly used as Ethernet backbone cable. Option 1 is correct. Because it requires fewer boosts to maintain the strength of the signal, coaxial cable can run for longer distances than either STP or UTP cable. Option 2 is incorrect. Because of its rigidity, Thicknet cable is difficult to install and, therefore, more expensive. Thicknet is only used for special-purpose installations. Option 3 is correct. Thicknet was traditionally used as Ethernet backbone cable owing to its noise rejection ability, and its ability to transmit data over great distances. xxviii Answer Fiber optic cable is used for modular light transmission, and cladding material is used to prevent light escaping from the core. Option 1 is correct. In a process called total internal reflection, cladding contains all light within the cable, while also allowing the light to travel around bends. Option 2 is incorrect. A fiber optic cable contains two parallel fibers which are both surrounded by a protective membrane. Option 3 is correct. The core fiber is made of pure glass, or high-grade plastic, capable of a high light-refraction index, and it transmits pulses of light that represent bits. Option 4 is incorrect. In fact, single-mode cable uses lasers to generate light. Multimode cable uses LEDs to generate light.
- 175. Study Notes http://SlideShare.net/OxfordCambridge 175| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n xxix Answer Coaxial cable was traditionally used to cable Ethernet backbones, fiber optic cable transmits pulses of light, and UTP cable has a maximum transmission length of 100 meters. Thicknet can transmit data over great distances, and has a strong noise reduction capacity, making it very effective on Ethernet backbones. Fiber optic cable transmits pulses of light that represent bits, instead of transmitting electrical signals. It is comparatively expensive. UTP cable is easy to work with, because it has a narrow gauge and is suitable for cabling that involves a lot of twists and turns. xxx Answer BNC is used to connect Thinnet coaxial cable. Option 1 is incorrect. AUI/DB-15 connectors are used with thick Ethernet cable. Option 2 is correct. The BNC has male and female type connectors, with the male connector always attached to the each end of a cable. Option 3 is incorrect. F-type is normally used with coaxial cable on wireless access points and bridges. Option 4 is incorrect. The RJ-45 is typically used with UTP cables and is commonly used to connect computers onto Ethernet LANs. xxxi Answer The ST connector is the most widely used fiber optic connector. It has a metal housing similar to the coaxial BNC attachment mechanism with Thinnet. Option 1 is incorrect. The LC has a plastic housing and a locking tab. Option 2 is incorrect. The MT-RJ connector has a plastic housing and metal guide pins. Option 3 is correct. The ST connector was developed by AT&T and the two versions of it are ST and ST-II. They are keyed and spring-loaded and are push-in and twist-type connectors. Option 4 is incorrect. The SC is one of the most common type of fiber optic connectors used – it is a low cost, simple, durable connector. xxxii Answer The IEEE 1394b sub-standard supports data transfer rates of up to a maximum of 800 Mbps.
- 176. Study Notes http://SlideShare.net/OxfordCambridge 176| P a g e C o m p u t e r N e t w o r k s F o u n d a t i o n Option 1 is incorrect. Data transfer rates of up to a maximum of 800 Mbps are supported by the IEEE 1394b standard. Option 2 is incorrect. The IEEE 1394b sub-standard supports data transfer rates of over 600Mbps. The maximum speed it supports is 800 Mbps. Option 3 is correct. The IEEE 1394b sub-standard supports data transfer rates of up to a maximum of 800 Mbps. xxxiii Answer You use a punchdown tool to attach a twisted pair cable to an IDC. Option 1 is incorrect. Crimpers are primarily used to attach connectors onto different types of network cables by a process known as crimping. Option 2 is incorrect. A patch panel port is connected to the hub using a patch cable. Option 3 is correct. Punchdown tools are commonly used to attach twisted pair cables to an IDC, typically used in patch panels. The tool presses the conductor against the sides of a metal "V" in the IDC. xxxiv Answer You use a wire map tester to make sure that the wires at one end of the cable are connected to the correct pins at the other end. Option 1 is correct. A wire map tester transmits signals through each wire in a copper twisted pair cable to determine if it is connected to the correct pin at the other end. Option 2 is incorrect. Continuity testers check copper cable connections for basic installation problems, such as opens, shorts, and crossed pairs. Option 3 is incorrect. Tone generators are used to locate a specific connection in a punchdown block. Option 4 is incorrect. An OLTS is a combined optical power meter and test source and is used for testing fiber optic network cables.