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本试卷共3页，第1页东北大学考试试卷2017—2018学年第一学期课程名称：ComputerNetworks（Test1）┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄总分一二三四五六七八学院班级学号姓名……………○……………密……………○……………封……………○…………线………………………………I.MultipleChoices(20points,2foreach)()1.Servicesprovidedbydatalinklayerprotocolsdonotinclude:A.framingB.transparenttransmissionC.congestioncontrolD.errorcontrol()2.Ethernetswitchesforwardpacketsaccordingto:A.destinationIPaddressB.destinationportnumberC.destinationMACaddressD.destinationhostdomainname()3.AccordingtothemechanismofCSMA/CDprotocol,whichofthefollowingsituationneedtoincreasetheshortestlengthofframes:A.keepthenetworktransmissionrate,andshortenthemaximumdistanceofcollisiondomain.B.keepthemaximumdistanceofcollisiondomain,andincreasethenetworktransmissionrate.C.extendthecoverageofnetworkusingbridges.D.increasethenumberofhosts.()4.Ethernetswitchesare:A.multi-portrepeatersatLayer1.B.multi-portbridgesatLayer2.C.multi-portswitchesatLayer2.D.multi-portroutersatLayer3.()5.TheservicethatEthernetdoesn’tprovideis:A.framingB.reliabledeliveryC.errordetectionD.mediumaccess()6.Whichofthefollowingisnotacomponentofnetworkprotocols:A.syntaxB.semanticsC.synchronizationD.architecture()7.TheMACprotocolusedby802.11WLANis:A.CSMA/CAB.CSMA/CDC.CSMAD.CDMA()8.Thetransmissionmediabelowwhichisnotaffectedbyelectromagneticinterferenceis:A.STPB.coaxC.fiberD.UTP()9.Whenahostismovedfromonenetworktoanother,whichofthefollowingiscorrect:A.BoththeIPaddressandMACaddressshouldbechanged.B.TheIPaddressmaybechanged,andtheMACaddressshouldnotbechanged.C.TheMACaddressmustbechanged,andtheIPaddressshouldnotbechanged.D.NeithertheIPaddressnorMACaddressshouldbechanged.()10.Concerning100BASE-T,whichofthefollowingiswrong:A.Thetransmissionrateis100Mbit/s.B.Thesignalisbasebandsignal.C.ThemediatakesType5UTP,andthemaximumdistanceis185m.D.Bothsharingandswitchingnetworkingapproachesaresupported.II.FillintheBlanks(10points,1foreachblank)1.TheMTUofEthernetisoflengthbytes.2.Computernetworkstakeswitchingapproach,whilethetraditionaltelephonenetworkstakeswitchingapproach.3.Theminimumlengthofframetransmittedby802.3Ethernetisbytes.4.ARPtableskeepthemappingfromaddressestoaddresses.5.Incomputernetworks,thetwocommunicationpartiesmustobeysomecommonrulesorconventions,whicharecalled.6.Fromthepointthattwocommunicationpartiesexchangeinformationofview,therearethreebasicways,i.e.,,and.III.TrueorFalse(10points,1foreach)()1.Ethernetswitchescanseparatecollisiondomains,soitcancontrolbroadcaststorm.()2.CSMA/CDprotocolcanonlyworkinhalf-duplexmode.()3.Ethernetprovidesconnectionless,unreliabledatatransfer.()4.Twisted-pairsisakindoftransmissionmediawhichhasbroadestbandwidth,leastsignaltransmissionattenuationandbestanti-jammingcapability.()5.Thebasicconceptofnetworkarchitectureislayering,andthecoreisthecommunicationbetweenentities.Inordertomaketheentitiescommnicatable,theymustobeysomecommonregulations,whichareprotocols.()6.TCP/IPcanbeusedforcommunicationbetweendifferentprocessesonthesamehost.()7.Eightbroadcastdomainsarecreatedwhenyousegmentanetworkwithan8-portswitch.()8.ThebasicprincipleofISOnetworkprotocollayeringisthatdifferentnodeshavedifferentlayersandthesamelayerofdifferentnodesprovidesthesamefunctions.()9.AsinEthernet,accesscollisionsmayalsohappenintokenringnetworks.()10.ThemostcommonlyusedWANtopologyisstartopology.IV.Terminology(10points,2foreach)1.ARP2.CSMA/CD3.ISP4.PPP5.PDU本试卷共3页，第2页学院班级学号姓名……………○……………密……………○……………封……………○…………线………………………………3.Considerdelayswithmultiplelinks.(12points)a.ConsiderapacketoflengthLwhichbeginsatendsystemA,travelsoveronelinktoapacketswitch,andtravelsfromthepacketswitchoverasecondlinktoadestinationendsystem.Letdi,siandRidenotethelength,propagationspeed,andtransmissionrateoflinki,fori=1,2.Thepacketswitchdelayseachpacketbydproc.Assumingnoqueuingdelays,intermsofdi,si,Ri,(i=1,2)andL,whatisthetotalend-to-enddelayforthepacket?Supposethepacketis1,000bytes,thepropagationspeedonbothlinksis2.5*108m/sthetransmissionratesofbothlinksis1Mbps,thepacketswitchprocessingdelayis1msec,thelengthofthefirstlinkis4,000km,andthelengthofthelastlinkis1,000km.Forthesevalues,whatistheend-to-enddelay?b.NowsupposeR1=R2=Randdproc=0.Furthermore,supposethepacketswitchdoesnotstore-and-forwardpacketsbutinsteadimmediatelytransmitseachbititreceivesbeforewaitingforthepackettoarrive.Whatistheend-to-enddelay?V.ComprehensiveQuestions(25point)1.ConsidertheTCP/IPprotocolsuite,providethenameofeachlayerandlistthenameofprotocoldataunitcorrespondingtoeachlayer.(5points)2.ConsidertwonodesAandBonthesameEthernetsegment,andsupposethepropagationdelaybetweenthetwonodesis225bittimes.Supposeattimet=0bothnodesAandBbegintotransmitaframe.Atwhattime(inbittimes)dotheydetectthecollision?Assumingbothnodestransmita48-bitjamsignalafterdetectingacollision,atwhattime(inbittimes)donodesAandBsenseanidlechannel?Howmanysecondsisthisfora10MbpsEthernet?(8points)本试卷共3页，第3页学院班级学号姓名……………○……………密……………○……………封……………○…………线………………………………2.Inthedatalinklayer,westudiedanumberofmultipleaccessprotocols,includingTDMA,CSMA,slottedAloha,tokenpassing,etc.(15poi