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A01 STAL2052 09 SE FM.QXD6/29/105:25 PMPage iDATA AND COMPUTERCOMMUNICATIONS 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

A01 STAL2052 09 SE FM.QXD6/29/105:25 PMPage ii 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

A01 STAL2052 09 SE FM.QXD6/29/105:25 PMPage iiiDATA AND COMPUTERCOMMUNICATIONSNinth EditionWilliam StallingsPrentice HallBoston Columbus Indianapolis New York San Francisco Upper Saddle RiverAmsterdam Cape Town Dubai London Madrid Milan Munich Paris Montreal TorontoDelhi Mexico City Sao Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

A01 STAL2052 09 SE FM.QXD6/29/105:25 PMPage ivEditor in Chief: Michael HirschAcquisitions Editor: Tracy DunkelbergerAssistant Editor: Melinda HaggertyEditorial Assistant: Allison MichaelDirector of Marketing: Margaret WaplesMarketing Coordinator: Kathryn FerrantiManaging Editor: Jeffrey HolcombProject Manager: Wanda RockwellProduction Supervisor: Heather McNallyCreative and Art Director: Jayne ConteCover Designer: Suzanne BehnkeCover Art: ShutterstockMedia Editor: Daniel SandinMedia Project Manager: Katelyn BollerFull-Service Project Management: IntegraAccess the latest information about Prentice Hall titles from our World Wide Web site:http://www.pearsonhighered.com/csCredits and acknowledgments borrowed from other sources and reproduced, with permission, in this textbook appear onappropriate page within text.Microsoft and Windows are registered trademarks of the Microsoft Corporation in the U.S.A. and other countries.Screen shots and icons reprinted with permission from the Microsoft Corporation.This book is not sponsored or endorsedby or affiliated with the Microsoft Corporation.The programs and applications presented in this book have been included for their instructional value.They have been testedwith care, but are not guaranteed for any particular purpose.The publisher does not offer any warranties or representations, nordoes it accept any liabilities with respect to the programs or applications.Copyright 2011, 2007, 2004, 2000, 1997 Pearson Education, Inc., publishing as Prentice Hall, 1 Lake Street,Upper Saddle River, New Jersey, 07458. All rights reserved. Manufactured in the United States of America. Thispublication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibitedreproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical,photocopying, recording, or likewise. To obtain permission(s) to use material from this work, please submit a written requestto Pearson Education, Inc., Permissions Department, Prentice Hall, 1 Lake Street, Upper Saddle River, New Jersey, 07458.Many of the designations by manufacturers and sellers to distinguish their products are claimed as trademarks. Where thosedesignations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed ininitial caps or all caps.Library of Congress Cataloging-in-Publication DataStallings,William.Data and computer communications / William Stallings.—9th ed.p. cm.Includes bibliographical references and index.ISBN-13: 978-0-13-139205-2 (alk. paper)ISBN-10: 0-13-139205-0 (alk. paper)1. Data transmission systems. 2. Computer networks. I. Title.TK5105.S73 2011004.6--dc22201002505210 9 8 7 6 5 4 3 2 1—EB—15 14 13 11 10ISBN 10:0-13-139205-0ISBN 13: 978-0-13-139205-2 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

A01 STAL2052 09 SE FM.QXD6/29/105:25 PMPage vFor my brave, extraordinaryand fascinating wife ATS 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

A01 STAL2052 09 SE FM.QXD6/29/105:25 PMPage vi 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

A01 STAL2052 09 SE FM.QXD6/29/105:25 PMPage viiCONTENTSPrefacexvAcknowledgmentsxxiAbout the AuthorxxiiiAnimations DirectoryxxvChapter 0 Reader’s and Instructor’s Guide 10.1Outline of the Book 20.2A Roadmap for Readers and Instructors0.3Internet and Web Resources 50.4Standards 63PART ONE OVERVIEW 8Chapter 1 Data Communications, Data Networks, and the Internet 81.1Data Communications and Networking for Today’s Enterprise 91.2A Communications Model 161.3Data Communications 191.4Networks 221.5The Internet 251.6An Example Configuration 30Chapter 2 Protocol Architecture, TCP/IP, and Internet-Based Applications2.1The Need for a Protocol Architecture 332.2A Simple Protocol Architecture 342.3The TCP/IP Protocol Architecture 382.4Standardization within a Protocol Architecture 462.5Traditional Internet-Based Applications 492.6Multimedia 502.7Recommended Reading and Web Sites 532.8Key Terms, Review Questions, and Problems 54Appendix 2A The Trivial File Transfer Protocol 57PART TWO DATA COMMUNICATIONS 62Chapter 3 Data Transmission 623.1Concepts and Terminology 643.2Analog and Digital Data Transmission 753.3Transmission Impairments 833.4Channel Capacity 893.5Recommended Reading and Web Site 933.6Key Terms, Review Questions, and ProblemsAppendix 3A Decibels and Signal Strength 97Chapter 4 Transmission Media 1004.1Guided Transmission Media 1024.2Wireless Transmission 1163294 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.vii

A01 STAL2052 09 SE FM.QXDviii6/29/105:25 PMPage viiiCONTENTS4.3Wireless Propagation 1244.4Line-of-Sight Transmission 1294.5Recommended Reading and Web Sites 1334.6Key Terms, Review Questions, and Problems 134Chapter 5 Signal Encoding Techniques 1385.1Digital Data, Digital Signals 1415.2Digital Data, Analog Signals 1515.3Analog Data, Digital Signals 1625.4Analog Data, Analog Signals 1685.5Recommended Reading 1755.6Key Terms, Review Questions, and Problems 175Chapter 6 Digital Data Communication Techniques 1806.1Asynchronous and Synchronous Transmission 1826.2Types of Errors 1866.3Error Detection 1866.4Error Correction 1966.5Line Configurations 2026.6Recommended Reading 2036.7Key Terms, Review Questions, and Problems 204Chapter 7 Data Link Control Protocols 2087.1Flow Control 2107.2Error Control 2177.3High-Level Data Link Control (HDLC) 2237.4Recommended Reading 2307.5Key Terms, Review Questions, and Problems 230Appendix 7A Performance Issues 233Chapter 8 Multiplexing 2408.1Frequency Division Multiplexing 2438.2Synchronous Time Division Multiplexing 2498.3Statistical Time Division Multiplexing 2598.4Asymmetric Digital Subscriber Line 2668.5xDSL 2708.6Recommended Reading and Web Sites 2728.7Key Terms, Review Questions, and Problems 273Chapter 9 Spread Spectrum 2769.1The Concept of Spread Spectrum 2789.2Frequency-Hopping Spread Spectrum 2799.3Direct Sequence Spread Spectrum 2849.4Code Division Multiple Access 2909.5Recommended Reading and Web Site 2949.6Key Terms, Review Questions, and Problems 294 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

A01 STAL2052 09 SE FM.QXD6/29/105:25 PMPage ixCONTENTSPART THREE WIDE AREA NETWORKS 298Chapter 10 Circuit Switching and Packet Switching 29810.1Switched Communications Networks 30010.2Circuit-Switching Networks 30210.3Circuit-Switching Concepts 30510.4Softswitch Architecture 30910.5Packet-Switching Principles 31010.6Recommended Reading 32010.7Key Terms, Review Questions, and Problems 320Chapter 11 Asynchronous Transfer Mode 32311.1The Role of ATM 32511.2Protocol Architecture 32611.3ATM Logical Connections 32811.4ATM Cells 33311.5Transmission of ATM Cells 33911.6ATM Service Categories 34311.7Recommended Reading and Web Sites 34611.8Key Terms, Review Questions, and Problems 347Chapter 12 Routing in Switched Data Networks 35012.1Routing in Packet-Switching Networks 35112.2Examples: Routing in ARPANET 36112.3Least-Cost Algorithms 36712.4Recommended Reading 37212.5Key Terms, Review Questions, and Problems 373Chapter 13 Congestion Control in Data Networks 37713.1Effects of Congestion 37913.2Congestion Control 38413.3Traffic Management 38613.4Congestion Control in Packet-Switching Networks13.5ATM Traffic Management 38813.6ATM–GFR Traffic Management 40013.7Recommended Reading 40313.8Key Terms, Review Questions, and Problems 404Chapter 14 Cellular Wireless Networks 40714.1Principles of Cellular Networks 40814.2First-Generation Analog 42214.3Second-Generation CDMA 42314.4Third-Generation Systems 42914.4Fourth-Generation Systems 43314.5Recommended Reading and Web Sites 43814.6Key Terms, Review Questions, and Problems 439388 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.ix

A01 STAL2052 09 SE FM.QXDx6/29/105:25 PMPage xCONTENTSPART FOUR LOCAL AREA NETWORKS 442Chapter 15 Local Area Network Overview 44215.1Topologies and Transmission Media 44315.2LAN Protocol Architecture 44915.3Bridges 45715.4Hubs and Switches 46515.5Virtual LANs 46915.6Recommended Reading and Web Sites 47415.7Key Terms, Review Questions, and Problems 474Chapter 16 Ethernet 47716.1Traditional Ethernet 47916.2High-Speed Ethernet 48716.3IEEE 802.1Q VLAN Standard 49816.4Recommended Reading and Web Sites 50016.5Key Terms, Review Questions, and Problems 500Appendix 16A Digital Signal Encoding for LANs 503Appendix 16B Scrambling 510Chapter 17 Wireless LANs 51317.1Overview 51417.2Wireless LAN Technology 51917.3IEEE 802.11 Architecture and Services 52117.4IEEE 802.11 Medium Access Control 52617.5IEEE 802.11 Physical Layer 53317.6IEEE 802.11 Security Considerations 54117.7Recommended Reading and Web Sites 54217.8Key Terms, Review Questions, and Problems 543PART FIVE INTERNET AND TRANSPORTPROTOCOLS 545Chapter 18 Internet Protocols 54518.1Principles of Internetworking 54618.2Internet Protocol Operation 55118.3Internet Protocol 55818.4IPv6 56818.5Virtual Private Networks and IP Security 57718.6Recommended Reading and Web Sites 58018.7Key Terms, Review Questions, and Problems 581Chapter 19 Internetwork Operation 58519.1Multicasting 58619.2Routing Protocols 59619.3Mobile IP 60719.4Recommended Reading and Web Sites 61919.5Key Terms, Review Questions, and Problems 620 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

A01 STAL2052 09 SE FM.QXD6/29/105:25 PMPage xiCONTENTSChapter 20 Internetwork Quality of Service 62320.1Integrated Services Architecture 62520.2Resource Reservation Protocol 63420.3Differentiated Services 64420.4Service Level Agreements 65220.5IP Performance Metrics 65420.6Recommended Reading and Web Sites 65720.7Key Terms, Review Questions, and Problems 659Chapter 21 Multiprotocol Label Switching 66121.1The Role of MPLS 66321.2Backgrounds 66521.3MPLS Operation 66721.4Labels 67221.5FECs, LSPs, and Labels 67621.6Label Distribution 67821.7Traffic Engineering 68221.8Virtual Private Networks 68721.9Recommended Reading and Web Sites 68921.10Key Terms, Review Questions, and Problems 690Chapter 22 Transport Protocols 69222.1Connection-Oriented Transport Protocol Mechanisms22.2TCP 71222.3TCP Congestion Control 72022.4UDP 73122.5Recommended Reading and Web Sites 73222.6Key Terms, Review Questions, and Problems 733PART SIXChapter 2323.123.223.323.423.523.623.7Chapter 2424.124.224.324.424.524.624.724.8694NETWORK SECURITY 737Computer and Network Security Threats 737Computer Security Concepts 738Threats, Attacks, and Assets 740Intruders 746Malicious Software Overview 750Viruses,Worms, and Bots 754Recommended Reading and Web Sites 764Key Terms, Review Questions, and Problems 765Computer and Network Security Techniques 768Virtual Private Networks and IPsec 769SSL and TLS 772Wi-Fi Protected Access 776Intrusion Detection 779Firewalls 782Malware Defense 790Recommended Reading and Web sites 796Key Terms, Review Questions, and Problems 796 2011 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.xi