1.1 Chapter 1 Introduction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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. Components Data Representation Data Flow Topics discussed in this section:

1.3 Figure 1.1 Five components of data communication

1.4 Data Representation Text Numbers Images Audio Video Voice

1.5 Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)

NETWORKS A network is a set of devices (often referred to as nodes) connected by communication links. 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. Distributed Processing Network Criteria Physical Structures Network Models Categories of Networks Interconnection of Networks: Internetwork Topics discussed in this section:

1.7 Communication Devices: Examples Bluetooth alarm clock switch Wireless router Common communication devices Non-common communication devices Bluetooth watches

1.8 Network Criteria Performance: Throughput Delay Other criteria Reliability Security becoming more important now

1.9 Figure 1.3 Types of connections: point-to-point and multipoint

1.10 Figure 1.4 Categories of topology

1.11 Figure 1.5 A fully connected mesh topology (five devices) n(n-1) half-duplex links n(n-1)/2 duplex links

1.12 Figure 1.6 A star topology connecting four stations

1.13 Figure 1.7 A bus topology connecting three stations

1.14 Figure 1.8 A ring topology connecting six stations

1.15 Figure 1.9 A hybrid topology: a star backbone with three bus networks

1.16 Categories of Networks Local Area Networks (LAN) IEEE IEEE IEEE Metropolitan Area Networks (MAN) High-speed DSL Cable TV network Wide Area Networks (WAN) Frame Relay ATM

1.17 Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet

1.18 Figure 1.11 WANs: a switched WAN and a point-to-point WAN

1.19 Figure 1.12 A heterogeneous network made of four WANs and two LANs

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. A Brief History The Internet Today (ISPs-Internet Service Providers) Topics discussed in this section:

1.21 A Brief History 1961: Kleinrock - queueing theory shows effectiveness of packet-switching 1964: Baran - packet-switching in military nets 1967: ARPAnet conceived by Advanced Research Projects Agency 1969: first ARPAnet node operational 1972: ARPAnet demonstrated publicly NCP (Network Control Protocol) first host-host protocol first program ARPAnet has 15 nodes

1.22 Figure 1.13 Hierarchical organization of the Internet now

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. Protocols – similar to human language Standards – public recognized protocols for open market Standards Organizations Internet Standards – Internet draft, Request for Comment (RFC) Topics discussed in this section: