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1、UnitFiveTechnologyComputerNetworksIngeneralacomputernetwork,asweknowtoday,maybesaidtohavegottenitsstartwiththeARPANETdevelopmentinthelate1960sandearly1970s.TheinitialARPANETdesignhadadefinitestructureofnetworkarchitectureandintroducedanotherkeyconcept:protocollayering.始于ARP
2、ANET：AdvancedResearchProjectAgencyNetwork阿帕网络网络体系结构，网络构架['prəutəkɔl]协议['leiəriŋ]分层TCP/IPprotocol：TransmissionControlProtocol/InternetProtocol传输控制/网络通讯协议MuchofourpresentknowledgeaboutnetworkisadirectresultoftheARPANETproject.TheISO,inthelate1970s,formulatedareferencemodeltop
3、rovideacommonbasisforthecoordinationofstandardsdevelopmentsandtoallowexistingandevolvingstandardsactivitiestobeplacedintoperspectivewithoneanother.ISO国际标准化组织（InternationalStandardizationOrganization）参考[pə'spektiv]透视的；透视Theultimateaimwastoallowanapplicationprocessinanycomput
4、erthatsupportedtheapplicablestandardstofreelycommunicatewithanapplicationprocessinanyothercomputersupportingthesamestandard,irrespectiveofitsoriginofmanufacture.ThismodelwastermedtheISOReferenceModelforOpenSystemInterconnection.不考虑，不顾ISO开放系统互联参考模型Itshouldbestressed,however,
5、thatthismodelisnotconcernedwithspecificapplicationsofcomputercommunicationnetworks.Rather,itisconcernedwiththestructuringofthecommunicationsoftwarethatisneededtoprovideareliable,datatransparentcommunicationservice(whichisindependentofanyspecificmanufacturesequipmentorconven
6、tions)tosupportawiderangeofapplications.和...有关，涉及透明的通信业务Anetworkisaseriesofpointsinterconnectedbycommunicationlines,locatedatthepointsarecomputer,switchingdevices,and/oruserterminals.Atypicalnetworkincludesthefollowingcomponents:hostcomputers,nodes,terminalcontrollers,andte
7、rminals.切换设备用户终端节点，网点Thetwobasictypesofnetworksarelocal-area(LAN)andwide-areanetwork(WAN).Alocal-areanetworkistwoormorecomputersdirectlylinkedwithinasmallareasuchasaroom,building,orgroupofcloselyplacedbuildings.Awide-areanetworkistwoormorecomputersthataregeographicallydispe
8、rsedandlinkedbycommunicationfacilitiessuchasthetelephonesystemormicrowaverelays.微波
