计网-第二章作业

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1、Chapter2注：括弧之中红色标注为与课本习题对应的编号2.1,2・2节后作业:1.(R2)Foracommunicationsessionbetweenapairofprocesses,whichprocessisthedientandwhichistheserver?答：Theprocessisalways-onhostcalledtheserver;Theprocesswhichinitiatesthecommunicationistheclient2.(R3)Whatisthedifferencebetweennetwor

2、karchitectureandapplicationarchitecture?答：Networkarchitecturereferstotheorganizationofthecommunicationprocessintolayers.Applicationarchitecture,ontheotherhand,isdesignedbyanapplicationdeveloperanddicatesthebroadstructureoftheapplication.3・(R4)Whatinformationisusedbyapr

3、ocessrunningononehosttoidentifyaprocessrunningonanotherhost?答：TheIPaddressofthedestinationhostandtheportnumberofthedestinationsocket.4.(R7)Supposeyouwantedtodoatransactionfromaremoteclienttoaserverasfastaspossible.WouldyouuseUDPorTCP?Why?答：WewoulduseUDP.WithUDP,thetran

4、sactioncanbecompletedinoneroundtriptime-theclientsendsthetransactionrequestintoaUDPsocket,andtheserversendsthereplybacktotheclientsUDPsocket.WithTCP,aminimumoftwoRTTsareneeded一onetoset-uptheTCPconnection,andanotherfortheclienttosendtherequest,andfortheservertosendbackt

5、hereply.5.(R8)Listthefourbroadclassesofservicesthatatransportprotocolcanprovide.Foreachoftheserviceclasses,indicateifeitherUDPorTCP(orboth)providessuchaservice・答:(1)ReliableDataTransfer:TCPprovidesareliablebyte-streambetweenclientandserverbutUDPdoesnot.(2)Throughput:Ag

6、uaranteethatacertainvalueforthroughputwillbemaintained;Neither.(3)Timing:Aguaranteethatdatawillbedeliveredwithinaspecifiedamountoftime;Neither.(4)Security:Neither.6.(R9)WhydoHTTP,FTP,SMTP,andPOP3runontopofTCPratherthanonUDP?答：Theapplicationsassociatedwiththoseprotocols

7、requirethatallapplicationdatabereceivedinthecorrectorderandwithoutgaps.TCPprovidesthisservicewhereasUDPdoesnot.7.(Rll)Whatismeantbyahandshakingprotocol?答：Aprotocoluseshandshakingifthetwocommunicatingentitiesfirstexchangecontrolpacketsbeforesendingdatatoeachother.SMTPus

8、eshandshakingattheapplicationlayerwhereasHTTPdoesno匸2.3,2.4节后作业8・(R15)SupposeAlice,withaWeb-basede-mailaccount(suchas