(完整版)川大软院计网选择题答案Chapter3(含答案)

CHAPTER3:TRANSPORTLAYER1.Atransport-layerprotocolprovidesforlogicalcommunicationbetween___C_.A.RoutersB.HostsC.ApplicationprocessesD.Endsystems2.Transport-layerprotocolsrunin__D__.A.ServersB.ClientsC.RoutersD.Endsystems3.Intransportlayer,thesendsidebreaksapplicationmessagesinto___B_,passestonetworklayer.A.FramesB.SegmentsC.Data-gramsD.bitstreams4.Thereceivesideoftransportlayerreassemblessegmentsintomessages,passesto__A__layer.A.ApplicationB.NetworkingC.PhysicalD.MAC5.Servicesprovidedbytransportlayerinclude__C__.A.HTTPandFTPB.TCPandIPC.TCPandUDPD.SMTP6.WhichofthefollowingservicesisnotprovidedbyTCP?DA.In-orderdatatransfersB.ReliabledatatransfersandflowcontrolsC.CongestioncontrolsD.Delayguaranteesandbandwidthguarantees7.Thesetwominimaltransport-layerservices----___A_and____----aretheonlytwoservicesthatUDPprovidesA.process-to-processdatadelivery,errorcheckingB.congestioncontrol,reliabledatatransferC.flowcontrol,congestioncontrolD.In-orderdatatransfer,errorchecking8.UDPofferswhichofthefollowingbenefitsrelativetoTCP?CA.UDPguaranteesthatIndividualpacketsofatransmissionwillarriveinorderB.UDPsupportsaself-regulatingthrottlefeaturethatpreventsnetworksaturationC.UDPconsumesfewercomputerresourcesbynotmaintainingconnectionstateD.Noneoftheabove9.WhichofthefollowingapplicationsnormallyusesUDPservices?BA.SMTPB.StreamingmultimediaC.FTPD.HTTP10.Thejobofgatheringdatachunks,encapsulatingeachdatachunkwithheaderinformationtocreatesegmentsandpassingthesegmentstothenetworkiscalled__A__.A.multiplexingB.de-multiplexingC.forwardingD.routing11.Thisjobofdeliveringthedatainatransport-layersegmenttothecorrectsocketiscalled_B___.A.multiplexingB.de-multiplexingC.forwardingD.routing12.Portnumbersscopeis___B_to____.A.0,1023B.0,65535C.0,127D.0,25513.Theportnumbersrangingfrom__C__to____arecalledwell-knownportnumberandarerestricted.A.0,127B.0,65535C.0,1023D.0,25514.TheUDPheaderhasonlyfourfields,theyare__A__.A.Sourceportnumber,destinationportnumber,lengthandchecksumB.Sourceportnumber,destinationportnumber,sourceIPanddestinationIPC.sourceIP,destinationIP,sourceMACaddressanddestinationMACaddressD.sourceIP,destinationIP,sequencenumberandACKsequencenumber15.ThefieldofLengthinUDPsegmentspecifiesthelengthof___B_.A.theUDPsegment,notincludingtheheaderB.theUDPsegment,includingtheheaderC.theUDPsegmentsheaderD.theLengthfield16.WhichofthefollowingaboutTCPconnectionisnotcorrect?AA.ItisabroadcastconnectionB.Itisapoint-to-pointconnectionC.ItisapipelinedconnectionD.Itisafullduplexconnection17.InthefollowingfourdescriptionsaboutMSSandMTU,whichoneisnotcorrect?CA.TheMSSistypicallysetbyMTUB.TheMSSisthemaximumsizeoftheTCPsegmentincludingheadersC.TheMSSisthemaximumamountofapplication-layerdatainthesegmentD.TheMTUmeansthelargestlink-layerframe18.__A__isthebytestreamnumberoffirstbyteinthesegment.A.SequencenumberB.ACKnumberC.ChecksumD.portnumber19.__B__isthebytesequencenumbersofnextbyteexpectedfromotherside.A.SequencenumberB.ACKnumberC.ChecksumD.portnumber20.Inthefollowingfouroptions,whichoneiscorrect?DA.SupposethatthelastSampleRTTinaTCPconnectionisequalto1sec.ThenthecurrentvalueofTimeoutIntervalwillnecessarilybe1secB.ThetimeoutshouldbelessthantheconnectionsRTTC.SupposethatthelastSampleRTTinaTCPconnectionisequalto1sec.ThenthecurrentvalueofTimeoutIntervalwillnecessarilybe1secD.ThevariationsintheSampleRTTaresmoothedoutinthecomputationoftheEstimatedRTT21.Therearetwo16-bitintegers:1110011001100110,1101010101010101.Theirchecksumis__A__.A.0100010001000011B.1011101110111100C.1111111111111111D.100000000000000022.SupposehostAsendshostBoneTCPsegmentwithsequencenumber418,acknowledgementnumber571,and4bytesofdata.Thenthesequencenumberintheacknowledgementtothissegmentis_____C____A.422B.418C.571D.57523.BecauseTCPonlyacknowledgesbytesuptothefirstmissingbyteinthestream,TCPissaidtoprovide__D__.A.positiveACKsB.SelectiveacknowledgementsC.3duplicateACKsD.Cumulativeacknowledgements24.IfwedefineNtobethewindowsize,basetobethesequencenumberoftheoldestunacknowledgedpacket,andnext-seq-numtobethesmallestunusedsequencenumber,thentheinterval[nextseqnum,base+N-1]correspondstopacketthat__A__.A.canbesentimmediatelyB.havealreadybeentransmittedandacknowledgedC.cannotbeusedD.havebeensentbutnotyetacknowledged25.Whichofthefollowingisnotapipeliningprotocol.AA.Rdt1.0B.Go-Back-NC.SelectiverepeatD.TCP26.Whatisthemaindifferencebetweenstop-and-waitandpipelinedreliabledatatransferprotocol?BA.ThepipelinedprotocolusestheNAKpackets,whereasinthestop-and-waitprotocolsendersalwayswaitforACKpackets.B.Withthepipelinedprotocol,thesendercansendseveralpacketsinrow,whereasinthestop-and-waitprotocolthesendercannotsendthepacketsinrow.C.Withthepipelinedprotocol,thereceivermustsendoneACKforseveralpackets(cumulativeACK),whereasinthestop-and-waitprotocolthereceivercannotsendthecumulativeACK.D.Thepipelinedprotocolusestimeouts,whereasthestop-and-waitprotocoldoesnotusethetimeout.27.Fastretransmitmeansinthecasethat__D__duplicateACK-sarereceived,theTCPsenderresendsegmentbeforetimerexpires.A.6B.5C.4D.328.__B__isaspeeding-matchingservice-