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

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Chapter 1

Introduction

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

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1-1 DATA COMMUNICATIONS1-1 DATA COMMUNICATIONS

The term The term telecommunicationtelecommunication means communication at a means communication at a distance. distance. The word The word datadata refers to information presented in refers to information presented in whatever form is agreed upon by the parties creating and whatever form is agreed upon by the parties creating and using the data. using the data. Data communicationsData communications are the exchange of data between are the exchange of data between two devices via some form of transmission medium such two devices via some form of transmission medium such as a wire cable. as a wire cable.

ComponentsData RepresentationData Flow

Topics discussed in this section:Topics discussed in this section:

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Figure 1.1 Five components of data communication

1 Components1 Components

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•TextText•NumbersNumbers•ImagesImages•AudioAudio•VideoVideo

1 Data Representation1 Data Representation

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

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1-2 NETWORKS1-2 NETWORKS

A A networknetwork is a set of devices (often referred to as is a set of devices (often referred to as nodesnodes) ) connected by communication connected by communication linkslinks. A node can be a . A node can be a computer, printer, or any other device capable of sending computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the and/or receiving data generated by other nodes on the network.network.

Distributed ProcessingNetwork CriteriaPhysical StructuresNetwork ModelsCategories of NetworksInterconnection of Networks: Internetwork

Topics discussed in this section:Topics discussed in this section:

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1-2 NETWORKS1-2 NETWORKS

Distributed Processing

When a task is divided among multiple computers

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1-2 NETWORKS1-2 NETWORKS

Network Criteria

Performance: transit time, response time, Performance: transit time, response time, throughput and delaythroughput and delay

Reliability: frequency of failure, recovery Reliability: frequency of failure, recovery time, and robustnesstime, and robustness

Security: protection from unauthorized Security: protection from unauthorized access, data damage and unauthorized access, data damage and unauthorized developmentdevelopment

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

Physical Structures

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Figure 1.4 Categories of topology

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Figure 1.5 A fully connected mesh topology (five devices)

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Figure 1.6 A star topology connecting four stations

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Figure 1.7 A bus topology connecting three stations

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Figure 1.8 A ring topology connecting six stations

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

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

Categories of Networks

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

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

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1-3 THE INTERNET1-3 THE INTERNET

The The InternetInternet has revolutionized many aspects of our daily has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the lives. It has affected the way we do business as well as the way we spend our leisure time. The Internet is a way we spend our leisure time. The Internet is a communication system that has brought a wealth of communication system that has brought a wealth of information to our fingertips and organized it for our use. information to our fingertips and organized it for our use.

A Brief HistoryThe Internet Today (ISPs)

Topics discussed in this section:Topics discussed in this section:

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Figure 1.13 Hierarchical organization of the Internet

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1-4 PROTOCOLS AND STANDARDS1-4 PROTOCOLS AND STANDARDS

In this section, we define two widely used terms: In this section, we define two widely used terms: protocolsprotocols and and standardsstandards. First, we define protocol, which is . First, we define protocol, which is synonymous with rule. Then we discuss standards, which synonymous with rule. Then we discuss standards, which are agreed-upon rules.are agreed-upon rules.

ProtocolsStandardsStandards OrganizationsInternet Standards

Topics discussed in this section:Topics discussed in this section:

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1-4 PROTOCOLS1-4 PROTOCOLS

Syntax: structure or format

Semantics: meaning of section of bits

Timing: when data should be sent and how fast it can be sent

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1-4 STANDARDS1-4 STANDARDS

De facto

De jure