数据通信与网络教程(英文版.第2版)

The first edition of this book first appeared four years ago; much in the fields of data communications and computer networks has changed since then. Probably most visible is the emergence of the World Wide Web (WWW) and the many applications it supports. Perhaps less visible is the impact the Web has had on underlying network protocols to support these applications and the increased importance of issues involving privacy and security. In just a few years the scope of network users has changed forever. Not long ago most network users were primarily professionals,who might use email occasionally to talk to colleagues or request some vital information. Now network users number in the tens of millions and their uses range from professional needs to purely recreational activities. Although much of this book's content has changed, its purpose is still fundamentally tbe same. It is designed for junior-level students in a computer science program who have a minimum of two semesters of programming and a knowledge of precalculus and discrete mathematics. It covers standard topics found in a typical introductory course in data communications and computer networks, such as transmission media, analog and digital signals, data transmissions, compression and encryption methods, network topologies, data security, Ethernets and token ring protocols, wide area network protocols, and World Wide Web applications.

CHAPTER 1 INIRODUCTION TO COMMUNICATIONS, STANOARDS,
AND PTOTOCOLS

1 .1 WHY STUDY CoMMUNICATIONS?
A Brief History I · Applications 3 · Issues 6

1 .2 COMPUTER NETWORKS
Common Bus Topology 9 · Star Topology IO ·
Ring Topology 11· Fully Connected Topology l2 · Combined Topologies l3

1.3 STANDARDS AND STANDARDS ORGANIZATIONS
The Need for STandards 14 v Agencies l5

1.4 OPEN SYSTEMS AND THE OSI MODEL
Overview of the Model 20 · Physical Layer 23·Data Link Layer 28 · Network Layer 30· Transport
Layer 32 · Session Layer 38 · Presentation Layer 42 · Application Layer 45 · Summary 46

1.5 THE FUTURE OF DATA CoMMUNICTIONS
REVIEW QUESTIONS 51 ·EXERCISE5 53 · REFETENCES 54(HAPIER 2 IRANSMISSON FUNDAMENTALS

PURPO5E The first edition of this book first appeared four years ago; much in the fields of data communications and computer networks has changed since then. Probably most visible is the emergence of the World Wide Web (WWW) and the many applications it supports. Perhaps less visible is the impact the Web has had on underlying network protocols to support these applications and the increased importance of issues involving privacy and security. In just a few years the scope of network users has changed forever. Not long ago most ne..