计算机网络(双语)Andrew-S.Tanenbaum第五版(第一章)CN-chapter1

COMPUTERNETWORKSTEACHER:HUANUsesofcomputernetworksNetworkhardwareNetworksoftwareReferencemodels1Usesofcomputernetworks•Sharingproblems•Piracy•Privacy•Lawproblems•Smartphone•GPS•M-commerce•Wearablecomputer•Twitter•Youtube•Facebook•Ubiquitouscomputing•Resourcesharing(VPN)•E-mail•Desktopsharing•E-commerceBusinessapplicatictionsHomeapplicationsSocialissuesMobileusersUsesofcomputernetworksNetworkhardwareNetworksoftwareReferencemodels2.1Networkhardware-transmissiontechnology•Point-to-pointlinksconnectindividualpairsofmachinesPoint-to-point•Onabroadcastnetwork,thecommunicationchannelissharedbyallthemachinesonthenetworkbroadcast2.2Networkhardware-scale2.2.1Networkhardware-scalePersonalAreaNetworks2.2.2Networkhardware-scaleLocalAreaNetworks2.2.3Networkhardware-scaleMetropolitanAreaNetworks2.2.4Networkhardware-scaleWideAreaNetworksUsesofcomputernetworksNetworkhardwareNetworksoftwareReferencemodels3NetworksoftwareNetworkarchitectureserviceConnect-orientedserviceConnectlessserviceProtocolLayer3.1Networksoftware-layerlayerToreducetheirdesigncomplexity,mostnetworksareorganizedasastackoflayersorlevels,eachonebuiltupontheonebelowit.Thepurposeofeachlayeristooffercertainservicestothehigherlayerswhileshieldingthoselayersfromthedetailsofhowtheofferedservicesareactuallyimplemented.3.2Networksoftware-protocolprotocolAprotocolisanagreementbetweenthecommunicatingpartiesonhowcommunicationistoproceed.Asananalogy,whenawomanisintroducedtoaman,shemaychoosetostickoutherhand.He,inturn,maydecidetoeithershakeitorkissit,depending,forexample,onwhethersheisanAmericanlawyeratabusinessmeetingoraEuropeanprincessataformalball.Violatingtheprotocolwillmakecommunicationmoredifficult,ifnotcompletelyimpossible.3.3Networksoftware-interfaceinterfaceInterfaceisaconnectionpointwhichexchangeofinformationbetweentheadjacentlayers.Theinterfacedefineswhichprimitiveoperationsandservicesthelowerlayermakesavailabletotheupperone.3.4Networksoftware-serviceserviceAserviceisasetofoperationsthatalayerprovidestothelayeraboveit.Aservicerelatestoaninterfacebetweentwolayers,withthelowerlayerbeingtheserviceproviderandtheupperlayerbeingtheserviceuser.Layerscanoffertwodifferenttypesofservicetothelayersabovethem:connection-orientedandconnectionless.3Networksoftware3.4Networksoftware-networkarchitecturenetworkarchitectureAsetoflayersandprotocolsiscalledanetworkarchitecture.DutchUsesofcomputernetworksNetworkhardwareNetworksoftwareReferencemodels4ReferencemodelsAlthoughtheprotocolsassociatedwiththeOSImodelarenotusedanymore,themodelitselfisactuallyquitegeneralandstillvalid,andthefeaturesdiscussedateachlayerarestillveryimportant.TheTCP/IPmodelhastheoppositeproperties:themodelitselfisnotofmuchusebuttheprotocolsarewidelyused.Sincecomputerscientistsliketohavetheircakeandeatit,too,wewillusethehybridmodelofFig.1-23astheframeworkforthisbook.4.1Referencemodels-OSI4.1Referencemodels-OSI4.2Referencemodels-TCP/IP4.3Referencemodels-UsedinThisBook目前在计算机网络领域有影响的标准化组织：1、国际电信联盟（ITU)2、国际标准化组织（ISO）3、电子工业协会（EIA）4、电气与电子工程师协会（IEEE）5、ATM论坛