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  1. 1. Chapter 1 Introduction 1.1
  2. 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 communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. 1.2
  3. 3. Figure 1.1 Five components of data communication 1.3
  4. 4. Data Representation 1- Text represented as a bit pattern ( code) 2- Numbers 3- Images its composed of a matrix 4- Audio it is a continuous signal 5- Video 1.4
  5. 5. Figure 1.2 Data flow (simplex, half-duplex, and full-duplex) 1.5
  6. 6. 1-2 NETWORKS A network is a set of devices (often referred to as nodes) connected by communication links(network medium). A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. Nodes use a common network protocol to share resources with each other. Topics discussed in this section: Distributed Processing Network Criteria Physical Structures Network Models Categories of Networks Interconnection of Networks: Internetwork 1.6
  7. 7. 1-2 NETWORKS Network criteria : Performance measured in transit time, response time Transit time : amount of time required for a message to travel from device to device. Response time : elapsed time between an inquiry and a response. performance is evaluated by 2 networking metrics :Throughput and Delay Reliability : Accuracy of delivery, frequency of failure, the time it takes a link to recover from failure. Security : protecting data from unauthorized access, protecting data from damage and development 1.7
  8. 8. Figure 1.3 Types of connections: point-to-point and multipoint 1.8
  9. 9. Figure 1.4 Categories of topology 1.9
  10. 10. Figure 1.5 A fully connected mesh topology (five devices) 1.10
  11. 11. Figure 1.6 A star topology connecting four stations 1.11
  12. 12. Figure 1.7 A bus topology connecting three stations 1.12
  13. 13. Figure 1.8 A ring topology connecting six stations 1.13
  14. 14. Figure 1.9 A hybrid topology: a star backbone with three bus networks 1.14
  15. 15. Categories of Networks The category into which a network falls is determined by its size Local Area Network: -LAN size is limited to a few kilometers -LAN can be as simple as 2 computers and a printer -IN addition to size, LAN is distinguished from other types of networks by transmission media and topology. - early LAN data flow rates from 4 to 6 Mbps, Now it is from 100 to 1000 Mbps Wide Area Network: 1.15
  16. 16. Figure 1.11 WANs: a switched WAN and a point-to-point WAN 1.16
  17. 17. Figure 1.12 A heterogeneous network made of four WANs and two LANs 1.17
  18. 18. 1-3 THE INTERNET The Internet has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time. The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use. Topics discussed in this section: A Brief History The Internet Today (ISPs) 1.18
  19. 19. Figure 1.13 Hierarchical organization of the Internet 1.19
  20. 20. 1-4 PROTOCOLS AND STANDARDS In this section, we define two widely used terms: protocols and standards. First, we define protocol, which is synonymous with rule. Then we discuss standards, which are agreed-upon rules. Topics discussed in this section: Protocols Standards Standards Organizations Internet Standards 1.20