Table Of Content

Computer Networks and Internets FIFTH EDITION This page intentionally left blank Computer Networks and Internets FIFTH EDITION DOUGLAS E. COMER Cisco Research Cisco, Inc. San Jose, CA 95138 and Department of Computer Sciences Purdue University West Lafayette, IN47907 Upper Saddle River, New Jersey 07458 Library of Congress Cataloging-in Publication Data on File. Editorial Director, Computer Science and Engineering: Marcia J. Horton Editorial Assistant: Melinda Haggerty Director of Marketing: Margaret Whaples Marketing Manager:Christopher Kelly Associate Editor: ReeAnne Davies Senior Managing Editor: Scott Disanno Production Editor: Irwin Zucker Art Director: Kenny Beck Cover Art: ©Sebastian Kaulitzki/Shutterstock Art Editor: Gregory Dulles Media Editor: David Alick Manufacturing Manager: Alan Fischer Manufacturing Buyer: Lisa McDowell ©2009, 2004, 2001, 1999, 1997 by Pearson Education, Inc. Upper Saddle River, New Jersey, 07458. All rights reserved. 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Pearson Education, Upper Saddle River, New Jersey 10 9 8 7 6 5 4 3 2 1 ISBN 10: 0-13-606127-3 ISBN 13: 978-0-13-606127-4 To PacketsEverywhere This page intentionally left blank Contents Preface xxiii PART I Introduction And Internet Applications 39 Chapter1 IntroductionAndOverview 1 1.1 Growth OfComputer Networking 1 1.2 WhyNetworking SeemsComplex 2 1.3 TheFiveKeyAspectsOf Networking 2 1.4 PublicAndPrivateParts Of TheInternet 6 1.5 Networks, Interoperability,AndStandards 8 1.6 ProtocolSuites AndLayeringModels 9 1.7 How DataPassesThrough Layers 11 1.8 HeadersAndLayers 12 1.9 ISOandtheOSISevenLayerReferenceModel 13 1.10 TheInsideScoop 13 1.11 RemainderOf TheText 14 1.12 Summary 15 Chapter2 InternetTrends 17 2.1 Introduction 17 2.2 ResourceSharing 17 2.3 Growth OfTheInternet 18 2.4 FromResourceSharing To Communication 21 2.5 FromTextTo Multimedia 21 2.6 RecentTrends 22 2.7 Summary 23 viii Contents Chapter3 InternetApplicationsAndNetworkProgramming 27 3.1 Introduction 27 3.2 Two BasicInternetCommunication Paradigms 28 3.3 Connection-orientedCommunication 29 3.4 TheClient-ServerModelOfInteraction 30 3.5 Characteristics OfClients AndServers 31 3.6 ServerProgramsAndServer-ClassComputers 31 3.7 Requests,Responses,AndDirectionOfDataFlow 32 3.8 Multiple Clients AndMultiple Servers 32 3.9 ServerIdentification AndDemultiplexing 33 3.10 ConcurrentServers 34 3.11 Circular DependenciesAmongServers 35 3.12 Peer-To-PeerInteractions 35 3.13 Network ProgrammingAndTheSocketAPI 36 3.14 Sockets,Descriptors,AndNetwork I/O 36 3.15 ParametersAndThe SocketAPI 37 3.16 SocketCalls InAClient AndServer 38 3.17 SocketFunctions UsedByBoth Client AndServer 38 3.18 TheConnectionFunctionUsedOnlyByAClient 40 3.19 SocketFunctions UsedOnlyByAServer 40 3.20 SocketFunctions UsedWith TheMessageParadigm 43 3.21 OtherSocketFunctions 44 3.22 Sockets,Threads, AndInheritance 45 3.23 Summary 45 Chapter4 TraditionalInternetApplications 49 4.1 Introduction 49 4.2 Application-LayerProtocols 49 4.3 RepresentationAndTransfer 50 4.4 WebProtocols 51 4.5 DocumentRepresentationWith HTML 52 4.6 Uniform ResourceLocators AndHyperlinks 54 4.7 WebDocumentTransfer With HTTP 55 4.8 Caching InBrowsers 57 4.9 Browser Architecture 59 4.10 FileTransfer Protocol(FTP) 59 4.11 FTP Communication Paradigm 60 4.12 ElectronicMail 63 4.13 TheSimpleMail Transfer Protocol (SMTP) 64 4.14 ISPs,Mail Servers,AndMail Access 66 4.15 Mail AccessProtocols (POP,IMAP) 67 Contents ix 4.16 Email RepresentationStandards (RFC2822,MIME) 67 4.17 DomainNameSystem(DNS) 69 4.18 DomainNamesThat BeginWith www 71 4.19 TheDNS HierarchyAndServerModel 72 4.20 NameResolution 72 4.21 Caching InDNS Servers 74 4.22 TypesOfDNS Entries 75 4.23 Aliases AndCNAME ResourceRecords 76 4.24 AbbreviationsAndTheDNS 76 4.25 Internationalized DomainNames 77 4.26 ExtensibleRepresentations(XML) 78 4.27 Summary 79 PART II Data Communication Basics 83 Chapter5 Overview OfDataCommunications 85 5.1 Introduction 85 5.2 TheEssenceOfDataCommunications 86 5.3 Motivation AndScopeOfTheSubject 87 5.4 TheConceptualPiecesOf ACommunication System 87 5.5 TheSubtopics Of DataCommunications 90 5.6 Summary 91 Chapter6 InformationSourcesAndSignals 93 6.1 Introduction 93 6.2 Information Sources 93 6.3 Analog AndDigital Signals 94 6.4 PeriodicAndAperiodicSignals 94 6.5 SineWavesAndSignal Characteristics 95 6.6 Composite Signals 97 6.7 TheImportanceOfComposite Signals AndSineFunctions 97 6.8 TimeAndFrequencyDomainRepresentations 98 6.9 Bandwidth OfAnAnalog Signal 99 6.10 Digital Signals AndSignal Levels 100 6.11 BaudAndBits PerSecond 101 6.12 ConvertingADigital Signal To Analog 102 6.13 TheBandwidth OfADigital Signal 103 6.14 SynchronizationAndAgreementAbout Signals 103 6.15 Line Coding 104