数据通信与网络cha

1.1,Chapter1Introduction,CopyrightTheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.,1.2,1-1DATACOMMUNICATIONS,Thetermtelecommunicationmeanscommunicationatadistance.Theworddatareferstoinformationpresentedinwhateverformisagreeduponbythepartiescreatingandusingthedata.Datacommunicationsaretheexchangeofdatabetweentwodevicesviasomeformoftransmissionmediumsuchasawirecable.,ComponentsDataRepresentationDataFlow,Topicsdiscussedinthissection:,1.3,Figure1.1Fivecomponentsofdatacommunication,1.4,Figure1.2Dataflow(simplex,half-duplex,andfull-duplex),1.5,1-2NETWORKS,Anetworkisasetofdevices(oftenreferredtoasnodes)connectedbycommunicationlinks.Anodecanbeacomputer,printer,oranyotherdevicecapableofsendingand/orreceivingdatageneratedbyothernodesonthenetwork.,DistributedProcessingNetworkCriteriaPhysicalStructuresNetworkModelsCategoriesofNetworksInterconnectionofNetworks:Internetwork,Topicsdiscussedinthissection:,1.6,Figure1.3Typesofconnections:point-to-pointandmultipoint,1.7,Figure1.4Categoriesoftopology,1.8,Figure1.5Afullyconnectedmeshtopology(fivedevices),1.9,Figure1.6Astartopologyconnectingfourstations,1.10,Figure1.7Abustopologyconnectingthreestations,1.11,Figure1.8Aringtopologyconnectingsixstations,1.12,Figure1.9Ahybridtopology:astarbackbonewiththreebusnetworks,1.13,Figure1.10AnisolatedLANconnecting12computerstoahubinacloset,1.14,Figure1.11WANs:aswitchedWANandapoint-to-pointWAN,1.15,Figure1.12AheterogeneousnetworkmadeoffourWANsandtwoLANs,1.16,1-3THEINTERNET,TheInternethasrevolutionizedmanyaspectsofourdailylives.Ithasaffectedthewaywedobusinessaswellasthewaywespendourleisuretime.TheInternetisacommunicationsystemthathasbroughtawealthofinformationtoourfingertipsandorganizeditforouruse.,ABriefHistoryTheInternetToday(ISPs),Topicsdiscussedinthissection:,1.17,Figure1.13HierarchicalorganizationoftheInternet,1.18,1-4PROTOCOLSANDSTANDARDS,Inthissection,wedefinetwowidelyusedterms:protocolsandstandards.First,wedefineprotocol,whichissynonymouswithrule.Thenwediscussstandards,whicharea