无线通信网络-第4章TCPIP协议族

ProtocolsandtheTCP/IPSuiteChapter4KeyFeaturesofaProtocolSyntaxConcernstheformatofthedatablocksSemanticsIncludescontrolinformationforcoordinationanderrorhandlingTimingIncludesspeedmatchingandsequencingAgentsInvolvedinCommunicationApplicationsExchangedatabetweencomputers(e.g.,electronicmail)ComputersConnectedtonetworksNetworksTransfersdatafromonecomputertoanotherTCP/IPLayersPhysicallayerNetworkaccesslayerInternetlayerHost-to-host,ortransportlayerApplicationlayerTCP/IPPhysicalLayerCoversthephysicalinterfacebetweenadatatransmissiondeviceandatransmissionmediumornetworkPhysicallayerspecifies:CharacteristicsofthetransmissionmediumThenatureofthesignalsThedatarateOtherrelatedmattersTCP/IPNetworkAccessLayerConcernedwiththeexchangeofdatabetweenanendsystemandthenetworktowhichit'sattachedSoftwareuseddependsontypeofnetworkCircuitswitchingPacketswitching(e.g.,X.25)LANs(e.g.,Ethernet)OthersT:TCP/IPInternetLayerUsesinternetprotocol(IP)ProvidesroutingfunctionstoallowdatatotraversemultipleinterconnectednetworksImplementedinendsystemsandroutersTCP/IPHost-to-Host,orTransportLayerCommonlyusestransmissioncontrolprotocol(tcp)ProvidesreliabilityduringdataexchangeCompletenessOrderTCP/IPApplicationLayerLogicsupportsuserapplicationsUsesseparatemodulesthatarepeculiartoeachdifferenttypeofapplicationProtocolDataUnits(PDUs)CommonTCP/IPApplicationsSimplemailtransferprotocol(SMTP)ProvidesabasicelectronicmailfacilityFileTransferProtocol(FTP)AllowsfilestobesentfromonesystemtoanotherTELNETProvidesaremotelogoncapabilityLayersoftheOSIModelApplicationPresentationSessionTransportNetworkDatalinkPhysicalOSIApplicationLayerProvidesaccesstotheOSIenvironmentforusersProvidesdistributedinformationservicesOSIPresentationLayerProvidesindependencetotheapplicationprocessesfromdifferencesindatarepresentation(syntax)OSISessionLayerProvidesthecontrolstructureforcommunicationbetweenapplicationsEstablishes,manages,andterminatesconnections(sessions)betweencooperatingapplicationsOSITransportLayerProvidesreliable,transparenttransferofdatabetweenendpointsProvidesend-to-enderrorrecoveryandflowcontrolOSINetworkLayerProvidesupperlayerswithindependencefromthedatatransmissionandswitchingtechnologiesusedtoconnectsystemsResponsibleforestablishing,maintaining,andterminatingconnectionsOSIDatalinkLayerProvidesforthereliabletransferofinformationacrossthephysicallinkSendsblocks(frames)withthenecessarysynchronization,errorcontrol,andflowcontrolOSIPhysicalLayerConcernedwithtransmissionofunstructuredbitstreamoverphysicalmediumDealswithaccessingthephysicalmediumMechanicalcharacteristicsElectricalcharacteristicsFunctionalcharacteristicsProceduralcharacteristicsComparisonofOSIandTCP/IPTCP/IPArchitectureDominanceTCP/IPprotocolsmaturedquickerthansimilarOSIprotocolsWhentheneedforinteroperabilityacrossnetworkswasrecognized,onlyTCP/IPwasavailableandreadytogoOSImodelisunnecessarilycomplexAccomplishesinsevenlayerswhatTCP/IPdoeswithfewerlayersElementsofStandardizationwithinOSIFrameworkProtocolSpecificationFormatofprotocoldataunits(PDUs)exchangedSemanticsofallfieldsAllowablesequenceofPDUsServiceDefinitionFunctionaldescriptionthatdefineswhatservicesareprovided,butnothowtheservicesaretobeprovidedAddressingEntitiesarereferencedbymeansofaserviceaccesspoint(SAP)InternetworkingTermsCommunicationnetwork–facilitythatprovidesadatatransferserviceamongdevicesattachedtothenetworkInternet–collectionofcommunicationnetworks,interconnectedbybridges/routersIntranet–internetusedbyanorganizationforinternalpurposesProvideskeyInternetapplicationsCanexistasanisolated,self-containedinternetInternetworkingTermsEndSystem(ES)–deviceusedtosupportend-userapplicationsorservicesIntermediateSystem(IS)–deviceusedtoconnecttwonetworksBridge–anISusedtoconnecttwoLANsthatusesimilarLANprotocolsRouter-anISusedtoconnecttwonetworksthatmayormaynotbesimilarFunctionsofaRouterProvidealinkbetweennetworksProvidefortheroutinganddeliveryofdatabetweenprocessesonendsystemsattachedtodifferentnetworksProvidethesefunctionsinsuchawayasnottorequiremodificationsofthenetworkingarchitectureofanyoftheattachedsubnetworksNetworkDifferencesRoutersMustAccommodateAddressingschemesDifferentschemesforassigningaddressesMaximumpacketsizesDifferentmaximumpacketsizesrequiressegmentationInterfacesDifferinghardwareandsoftwareinterfacesReliabilityNetworkmayprovideunreliableservice