（完整版）川大软院计网选择题答案Chapter1（含答案）

（完整版）川大软院计网选择题答案Chapter1（含答案）1.1Inthefollowingoptions,whichdoesnotdefineinprotocol?(D)AtheformatofmessagesexchangedbetweentwoormorecommunicatingentitiesBtheorderofmessagesexchangedbetweentwoormorecommunicatingentitiesCtheactionstakenonthetransmissionofamessageorothereventDthetransmissionsignalsaredigitalsignalsoranalogsignals1.2Inthefollowingoptions,whichisdefinedinprotocol?(A)Atheactionstakenonthetransmissionand/orreceiptofamessageorothereventBtheobjectsexchangedbetweencommunicatingentitiesCthecontentintheexchangedmessagesDthelocationofthehosts1.3Anapplicationcanrelyontheconnectiontodeliverallofitsdatawithouterrorandintheproperorder.Thesentencedescribes(C).AflowcontrolBcongestion-controlCreliabledatatransferDconnection-orientedservice1.4TheInternet’sconnection-orientedservicehasaname,itis(A).ATCPBUDPCTCP/IPDIP1.5TheInternet’sconnectionlessserviceiscalled(B).ATCPBUDPCTCP/IPDIP1.6Whichofthefollowingnodesbelongstothenetworkcore?CA.aWebServerB.aHostwithWin2003ServerC.aRouterwithNATserviceD.aSupernodeonSkypeNetwork1.7IntheInternet,theequivalentconcepttoendsystemsis()A.AhostsBserversCclientsDrouters1.8IntheInternet,endsystemsareconnectedtogetherby(C).AcopperwireBcoaxialcableCcommunicationlinksDfiberoptics1.9EndsystemsaccesstotheInternetthroughits(C).AmodemsBprotocolsCISPDsockets1.10Inthefollowingoptions,whichbelongstothenetworkcore?(B)AendsystemsBroutersCclientsDservers1.11Endsystems,packetswitches,andotherpiecesoftheInternet,run(D)thatcontrolthesendingandreceivingofinformationwithintheInternet.AprogramsBprocessesCapplicationsDprotocols1.12Theinternetallows(D)runningonitsendsystemstoexchangedatawitheachother.AclientsapplicationsBserverapplicationsCP2PapplicationsDdistributedapplications1.13Theprotocolsofvariouslayersarecalled(A).AtheprotocolstackBTCP/IPCISPDnetworkprotocol1.14IntheOSIreferencemodel,theupperlayersoftheOSImodelare,incorrectorderDASession,application,presentationBSession,presentation,applicationCSession,application,presentation,physicalDApplication,presentation,session1.15ThelowerlayersoftheOSImodelare,incorrectorderDAphysical,system,network,logicalBphysical,logical,network,systemCphysical,transport,network,datalinkDphysical,datalink,network,transport1.16TheInternetProtocol(IP)generallycorrespondstowhichOSIlayer?AANetwork(layerthree)BTransport(layerfour)CDatalink(layertwo)DSession(layerfive)1.17WhatlayeroftheOSImodelisdesignedtoperformerrordetectionfunctions?BAPhysicalBDatalinkCNetworkDtransport1.18WhichofthefollowingprotocollayersisnotexplicitlypartoftheInternetProtocolStack?_____B____A.applicationlayerB.sessionlayerC.datalinklayerD.transportlayer1.19The5-PDUiscalled__A_A.messageB.segmentC.datagramD.frame1.20TheInternet’snetworklayerisresponsibleformovingnetwork-layerpacketsknownasB()fromonehosttoanother.AframeBdatagramCsegmentDmessage1.21Transport-layerpacketsarecalled:BA.messageB.segmentC.datagramD.frame1.22Theunitsofdataexchangedbyalink-layerprotocolarecalled(A).AFramesBSegmentsCDatagramsDbitstreams1.23Therearetwofundamentalapproachestobuildinganetworkcore,(B)andpacketswitching.AelectricalcurrentswitchingBcircuitswitchingCdataswitchingDmessageswitching1.24Datagramnetworksandvirtual-circuitnetworksdifferinthat(C).Adatagramnetworksarecircuit-switchednetworks,andvirtual-circuitnetworksarepacket-switchednetworks.Bdatagramnetworksarepacket-switchednetworks,andvirtual-circuitnetworksarecircuit-switchednetworks.Cdatagramnetworksusedestinationaddressesandvirtual-circuitnetworksuseVC.numberstoforwardpacketstowardtheirdestination.DdatagramnetworksuseVC.numbersandvirtual-circuitnetworksusedestinationaddressestoforwardpacketstowardtheirdestination.1.25(A)meansthattheswitchmustreceivetheentirepacketbeforeitcanbegintotransmitthefirstbitofthepacketontotheoutboundlink.AStore-and-forwardtransmissionBFDMCEnd-to-endconnectionDTDM1.26In(C)networks,theresourcesneededalongapathtoprovideforcommunicationbetweentheendsystemarereservedforthedurationofthecommunicationsession.Apacket-switchedBdata-switchedCcircuit-switchedDmessage-switched1.27In(A)networks,theresourcesarenotreserved;asession’smessagesusetheresourcesondemand,andasaconsequence,mayhavetowaitforaccesstocommunicationlink.Apacket-switchedBdata-switchedCcircuit-switchedDmessage-switched1.28Inacircuit-switchednetwork,ifeachlinkhasncircuits,foreachlinkusedbytheend-to-endconnection,theconnectiongets(A)ofthelink’sbandwidthforthedurationoftheconnection.Aafraction1/nBallC1/2Dntimes1.29For(C),thetransmissionrateofacircuitisequaltotheframeratemultipliedbythenumberofbitsinaslot.ACDMABpacket-switchednetworkCTDMDFDM1.30Thenetworkthatforwardspacketsaccordingtohostdestinationaddressesiscalled(D)network.Acircuit-switchedBpacket-switchedCvirtual-circuitDdatagram1.31Thenetworkthatforwardspacketsaccordingtovirtual-circuitnumbersiscalled(C)network.Acircuit-switchedBpacket-switchedCvirtual-circuitDdatagram1.32Thetimerequiredtopropagatefromthebeginningofthelinktothenextrouteris(C).AqueuingdelayBprocessingdelayCpropagationdelayDtransmissiondelay1.33Processingdelaydoesnotincludethetimeto(B).Aexaminethepacket’sheaderBwaittotransmitthepacketontothelinkCdeterminewheretodirectthepacketDcheckbit-errorinthepacket1.34Inthefollowingfourdescriptions,whichoneiscorrect?(C)AThetrafficintensitymustbegreaterthan1.BThefractionoflostpacketsincreasesasthetrafficintensitydecreases.CIfthetrafficintensityisclosetozero,theaveragequeuingdelaywillbeclosetozero.DIfthetrafficintensityisclosetoone,theaveragequeuingdelaywillbeclosetoone.1.35Suppose,aistheaveragerateatwhichpacketsarriveatthequeue,Risthetransmissionrate,andallpacketsconsistofLbits,thenthetrafficintensityis(B),ALR／aBLa／RCRa／LDLR／a1.36Supposethereisexactlyonepacketswitchbetweenasendinghostandareceivinghost.ThetransmissionratesbetweenthesendinghostandtheswitchandbetweentheswitchandthereceivinghostareR1andR2,respectively.Assumingthattheswitchusesstore-and-forwardpacketswitching,whatisthetotalend-to-enddelaytosendapacketoflengthL?(Ignorequeuingdelay,propagationdelay,andprocessingdelay.)(A)AL/R1＋L/R2BL/R1CL/R2Dnoneoftheabove1.37Wearesendinga30MbitMP3filefromasourcehosttoadestinationhost.Supposethereisonlyonelinkbetweensourceanddestinationandthe