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Introduction to Data Communications and Networking
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Introduction to Data Communications and Networking


Data Communications and Networking Fourth Edition

Data Communications and Networking Fourth Edition

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  • 1. Chapter 1 Introduction1.1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  • 2. 1-1 DATA COMMUNICATIONS The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communication is the exchange of data between two devices via some form of transmission medium such as a wire cable. Topics discussed in this section: Components Data Representation Data Flow1.2
  • 3. 1-1 DATA COMMUNICATIONS For data communication to occur the communication devices must be part of some kind of communication system (hardware & software). Characteristics of Data Communication system: 1. Delivery 2. Accuracy 3. Timelines 4. Jitter1.3
  • 4. Figure 1.1 Five components of data communication1.4
  • 5. 1-1 Components 1. Message – data to be transferred 2. Sender – device that sends the message 3. Receiver – device that receives the message 4. Transmission Medium – a physical path by which message travels 5. Protocol – set of rules and guidelines that must be followed during the communication1.5
  • 6. 1-1 DATA REPRESENTATION 1. Text 2. Numbers 3. Images 4. Audio 5. Video1.6
  • 7. Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)1.7
  • 8. Data flow (simplex, half-duplex, and full-duplex)  Simplex  In simplex mode communication is unidirectional, as a one-way street. Only one of the two devices on a link can transmit; the other can only receive.  Examples: keyboards and traditional monitors1.8
  • 9. Data flow (simplex, half-duplex, and full-duplex)  Half Duplex  In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa.  Examples: Walkie-talkies and CB Radios1.9
  • 10. Data flow (simplex, half-duplex, and full-duplex)  Full Duplex  In full duplex mode, both stations can transmit and receive simultaneously.  It can be achieved by using two physically separate paths, one for sending and one for receiving, or by dividing the capacity of the channel between signals traveling in both directions  Examples: Telephone network1.10
  • 11. 1-2 NETWORKSA network is a set of devices (often referred to as nodes)connected by communication links. A node can be acomputer, printer, or any other device capable of sendingand/or receiving data generated by other nodes on thenetwork. Topics discussed in this section: Distributed Processing Network Criteria Physical Structures Network Models Categories of Networks Interconnection of Networks: Internetwork1.11
  • 12. 1-1 NETWORKS 1. Distributed Processing: 1. Network tasks are divided among several computers1.12
  • 13. 1-1 NETOWRKS 1. Network Criteria: 1. Performance: measured as throughput & delay 2. Reliability: frequency of failure – the time it takes for the link to recover from failure 3. Security: protection and breaches recovery 2. Physical Structures: 1. Point-to-Point: dedicated link between two devices 2. Multipoint: more than two devices share a single link1.13
  • 14. Figure 1.3 Types of connections: point-to-point and multipoint1.14
  • 15. Figure 1.4 Categories of topology1.15
  • 16. Figure 1.5 A fully connected mesh topology (five devices) Each device has a dedicated point-to-point link to every other device n(n-1)/21.16
  • 17. Figure 1.6 A star topology connecting four stations Each device has a dedicated point-to-point link only to a central controller called hub or switch1.17
  • 18. Figure 1.7 A bus topology connecting three stations One long cable acts as a backbone to link all the devices in the network1.18
  • 19. Figure 1.8 A ring topology connecting six stations Each device has a dedicated point-to-point connection with only two devices on either side of it.1.19
  • 20. Figure 1.9 A hybrid topology: a star backbone with three bus networks1.20
  • 21. Categories of Networks • LAN: Local Area Network • Its usually privately owned and links devices in a single office, building or campus. LAN can be as simple as two PC’s and a printer or it can extend throughout a company.1.21
  • 22. Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet1.22
  • 23. Categories of Networks • MAN: Metropolitan Area Network • Is a network with a size between a LAN and a WAN. It usually covers area within a town or a city.1.23
  • 24. Categories of Networks • WAN: Wide Area Network • Provides long-distance transmission of data image , audio and video information over large geographic areas that may comprise a country, a continent, or even the whole world1.24
  • 25. Figure 1.11 WANs: a switched WAN and a point-to-point WAN1.25
  • 26. Figure 1.12 A mixed network made of four WANs and two LANs1.26
  • 27. 1-3 THE INTERNETThe Internet has revolutionized many aspects of our dailylives. It has affected the way we do business as well as theway we spend our leisure time. The Internet is acommunication system that has brought a wealth ofinformation to our fingertips and organized it for our use.1.27
  • 28. Figure 1.13 Hierarchical organization of the Internet1.28
  • 29. 1-4 Protocols and Standards • For communication to occur, the communicating computers must agree an some protocol. • Protocol is a set of rules that govern data communications. The protocol, defines what is communicated, how it is communicated and when it is communicated. • Key elements: • Syntax – refers to the structure or format of data, meaning the order in which they are presented. • Semantics – refers to the meaning of each section of bits. • Timing – refers to two characteristics: when data should be sent and how fast should be sent1.29