2023-2024第二学期计算机网络试卷1A.docx

天津理工高校考试试卷20232023学年度第2学期计算机网络技术期末考试试卷课程代码：0600100试卷编号:1-A命题日期：2023年5月20日答题时限：120分钟考试形式：闭卷笔试PARTI:SingleChoice(1pointperquestion-total:20points)IiIStnIetiOns:SeIeCtoneofthelettersbesidethechoicethatisthebestanswerforeachquestion.得分Q1234567891011121314151617181920A1. WhichofthefollowingservicesdoestheInternetnetworklayerprovidefortheInternettransportlayer?a) In-orderdeliveryofdatasegmentsbetweenprocessesb) Besteffortdeliveryofdatasegmentsbetweencommunicatinghostsc) Multiplexinganddemultiplexingoftransportlayersegmentsd) Congestioncontrol2. ThemaintaskoftheIntemet,sDomainNameSystem(DNS)isto:a) TranslateportnumberstoIPaddressesb) SpecifythestandardsforInternetdomainnamesc) Provideanauthorityforregisteringdomainnamesd) TranslatemnemonicnamestoIPaddresses3. RDT3.0,sreceiverFSMissameto:a)RDTLOb)RDT2.1c)RDT2.2d)RDT2.04. TheTransmissionControlProtocol(TCP)provideswhichofthefollowingservices?a) End-to-endstationaddressingb) Applicationmultiplexingc) Internetworkroutingd) Mediumaccesscontrol(MAC)5. Whenadestinationhosttransportlayerreceivesdatafromthenetworklayer,itunambiguouslyidentifiestheappropriateprocesstopassthedatatobyusingatripletconsistingof:a) Sourceport#,destinationIPaddress,andsourceIPaddressb) Destinationport#,sourceport#,processID#a)Destinationport#,sourceport#,destinationIPaddressc) Destinationport#,sourceport#,sourceIPaddress6. Giventhattherequestedinformationisnotavailableatanyintermediatedatabases,anon-iteratedDNSqueryfromarequestinghostwouldfollowthepath:a) Rootnameserver,localnameserver,authoritativenameserverb) Authoritativenameserver,rootnameserver,hostnameserverc) 1.ocalnameserver,rootnameserver,localnameserver,authoritativenameserverd) 1.ocalnameserver,rootnameserver,authoritativenameserver7. Fromthelistbelow,selecttheitemsfoundintheTCPsegmentstructurethatarenotfoundintheUDPsegmentstructure:a) ApplicationGeneratedDatab) DestinationPort#c) SourcePort#a)Sequence#8. Selectthefouressentialsteps,brieflydescribed,forterminatingaTCPconnectionbetweenaclientandaserver,assumingthattheinitiatinghostistheclient:(1) ClientsendsTCPsegmentwithACKOandfinalsequencenumber(2) ClientsendsTCPsegmentwithFIN=1andgoesintoFIN_WAITstate(3) ServersendsTCPsegmenttoACKtheclient,sFINrequestandentersCLOSEWAITstate(4) ServersendsTCPsegmentwithFIN=O(5) ServersendsTCPsegmentwithFIN=I(6) ClientsendsTCPsegmentwithtoACKserver'sFINandenterssecondFINWAITstate(7) ClientsendsTCPsegmentwithFIN=Oa)2,3,5,6b)5,1,2,3c)1,3,5,7d)2,3,4,69. TheRIProutingprotocolisbasedonanalgorithmthatis:a) Basedoninformationreceivedonlyfromlink“neighbors”b) Alinkstatealgorithmc) AnOSPFalgorithmd) Acentralizedroutingalgorithm10. Whencompensatingforlinkcostchangesinthedistancevectoralgorithm,itcangenerallybesaidthat:a) Increasedcostsarepropagatedquickly,i.e.,ubadnewsntravelsfastb) Decreasedcostsarepropagatedrapidly,i.e.,4tgoodnews,*travelsfastc) Decreasedcostsdonotconverged) Noneoftheabovea) TwoimportantreasonsthattheInternetisorganizedasahierarchyofnetworksforthepurposesofroutingare:b) 1.eastcostandmaximumfreecircuitavailabilityc) Scaleandadministrativeautonomyd) Messagecomplexityandspeedofconvergencee) 1.inkcostchangesandlinkfailure11. Withanexteriorroutingprotocol,whichofthefollowingissuesgenerallydominatestheroutingdecisions?a) GeographicaldistancebetweenAS,sb) Policyc) NumberofAS,straversedd) CurrentcongestionlevelsintheAS,s12. ThehostcomponentofaCIDRaddressoftheformcancontainaddressesfor:a) 2(32-22)hosts(minusttspeciaF,hosts)b) 512hosts(minususpecia,hosts)c) dtimes22hostsd) 10hosts(minus4specia,hosts)13. AsanIPdatagramtravelsfromitssourcetoitsdestination:a) thesourceIPaddressischangedateachroutertoidentifythesendingrouterb) therouterusesthedestinationIPaddresstoconsultitsroutingtablec) therouterdoesnotusetheIPaddressesinthedatagramd) thedestinationIPaddressischangedateachroutertoreflectthenexthop14. Fromthelistbelow,choosethebitpatternwhichcouldbeavalidgeneratorvaluefortheCRCcode(R)11010:a)HlOb) OllOlOc) 100101d) 1001115. Theprimaryfunctionoftheaddressresolutionprotocol(ARP)thatresidesinInternethostsandroutersis:a) ToprovideLANrouterfunctionsb) TotranslatebetweenLANaddressesandphysicalinterfaceaddressesc) TotranslatebetweenIPaddressesandLANaddressesd) TocalculatetheshortestpathbetweentwonodesonaLAN16. Considersendinga1300byteIPv4datagramintoalinkthathasanMTUof500bytes:a) Threefragmentsarecreated.b) Fourfragmentsarecreated.c) Threefragmentsarecreatedwithoffsets0,5001000d) Thelastfragmentconsistsofexactly300bytesofdatafromtheoriginaldatagram17. SupposeoneIPv6routerwantstosendadatagramtoanotherIPv6router,butthetwoareconnectedtogetherviaaninterveningIPv4router.Ifthetworoutersusetunneling,then:a) ThesendingIPv6routercreatesanIPv4datagramandputsitinthedatafieldofanIPv6datagram.b) ThesendingIPv6routercreatesoneormoreIPv6fragments,noneofwhichislargerthanthemaximumsizeofanIPv4datagram.c) ThesendingIPv6routercreatesanIPv6datagramandputsitinthedatafieldofanIPv4datagram.d) ThesendingIPv6routercreatesanIPv6datagramandinterveningIPv4routerwillrejecttheIPv6datagram18. WhichofthefollowingwasanimportantconsiderationinthedesignofIPv6a) fixedlength40-byteheaderandspecifiedoptionstodecreaseprocessingtimeatIPv6nodesb) 128-bitaddressestoextendtheaddressspacec) differenttypesofservice(flows)definedd) alloftheabove19. Anetworkbridgetableisusedtoperformthefollowing:a) MappingMACaddressestobridgeportnumbersb) ForwardingframesdirectlytooutboundportsforMACaddressesithandlesc) Filtering(discarding)framesthatarenotdestinedforMACaddressesithandlesd) AlloftheabovePARTII:True/False(1pointsperquestion-total:15points)Instructions:Markthesymbolfctv,(forTrue)ifthestatementiscorrect,orthesymbol4,*(forFalse)ifthestatementisincorrect.得分Q123456789101112131415A1. TheInternet'sTransportLayerprotocolprovidesreliabledatatransferbetweenendsystems.2. NetworksshouldbedesignedsuchthattheTrafficIntensityvalueforeachnetworknodeislessthan1.3. ThemaximumsizeofasingleUDPsegmentislimitedto2,6-lbits.4. FTPusestwoseparateTCPconnections,onetoport20andonetoport21,andissaidtosenditscommands“outofband”.5. DuringthefirststepofaTCPconnectionhandshakebetweenaclientandaserver,theserverreceivesaTCPsegmentwithanullsequencenumberandtheSYNbitsetto1.6. TCPcongestioncontrolisdesignedtopreventbufferoverflowinnetworkend-systems.7. Duetothecharacteristicsofitscongestionavoidancealgorithm,TCPcanbesaidtobeatfaif,protocolwithregardtosharingavailablebandwidthamongusersofacommontransmissionlink.8. IntheInternet,interiorroutersinthesameautonomoussystemexecutethesameroutingalgorithmtocomputeroutingpaths.9. AlllinklayerprotocolsthatsupportIPhavethesameframestructure(i.e.,lengthofframe,numberandlengthofheaderfields).10. Routerssometimesusetransportlayerprotocols,suchasTCPorUDP,toexchangeroutingtableinformationwitheachother.11. AnynodeintheIPnetworkdefinedbywouldberequiredtohaveanIPaddressoftheform.12. PureAlohaismoreefficientthanSlotted-Aloha.13. Theentriesinabridgetableneedtobeconfiguredbythenetworkadministrator.14. 1.ayer-2switchescanbeusedtoisolateoneLANsegment,scollisiondomainfromthatofanotherLANsegment.15. TheTimeDivisionMultiplexing(TDM)channelpartitioningprotocolisappealingbecauseiteliminatescollisionsandisperfectlyfairwithregardtobandwidthavailability.PARTI11:Brieflyanswereachofthefollowingquestions.(1pointsperquestion-total:20points)得分1. Explainthedifferencebetweenconnection-orientedmessagingserviceandconnectionlessmessagingservice.2. Explainthedifferencebetweengo-back-Nandselectiverepeat.3. Wherecanqueuingoccurinarouter?Brieflyexplaintheconditionsthatleadtosuchqueuing.4. Satellitelinksoftenexhibithighpropagationtimesandlowtransmissionspeed.Whatdoesthismean?5. ThedifferencebetweenUDPandIPpacketsisminimal.Whyshouldn,tapplicationsuseIPdirectly?6. Cantwocomputersthathaveadifferentimplementationofthesameprotocolexchangemessages?Explainyouranswer.7. VVhatarethedifferencesbetweenroutingandforwarding?Brieflyexplaineachofthem.8. BrieflyexplaintheformulawlastByteSent-lastByteAcked<minCongWin,RcvWin,Ifnecessary,youcandrawafiguretodescribeyouranswer9. EthernetfollowsaCSMA/CDprotocolscheme.Explainhowthisschemeworks.10. Foraslidingwindowprotocol,itisnecessarytohavethewindowsizeatmosthalfoftherangeofsequencenumbers.Why?得分1. (total:6points)Considerthenetworkshownbelow.RunDijkstra,salgorithmtocomputetheshortestpathsfromAtoallothernodesinthenetwork.Whileselectingthenextnode,ifseveralnodeshavethesamemincost,selecttheonewithlowestid,(e.g.,ifBandDhavethesamemincost,thenselectB).Determinetheroutingtable(destination,next-node,andcost)atnodeA.DestinationNextNodeCostBCDEFGIJKLM2. (total:6points)Renocongestioncontrolalgorithm.ConsiderTCPReno(theonethatusesbothtimeoutand3duplicateACKstodetectpacketlosses).RememberthereceiversendscumulativeACKwheneverasegmentisreceivedandassumethatourTCPimplementationdiscardsout-of-ordersegments,soasinGo-Back-N,thesendershouldre-transmitallpacketsstartingfrombasewhenapacketlossisdetected.Remembercongestionwindowneedstobeadjustedbeforeretransmission.Aserverapplicationhas26TCPsegments(packets)(thatarenumberedas1,2,3.26)tosendtothereceiversite.Assumethatthesenderstartedfromslowstartwithacongestionwindowof1andcontinuedaccordingtoTCPRenocongestioncontrolalgorithm.TheinitialThresholdvaluewas4.ThetimeoutdurationatthesenderissettoRTT.AssumethatthesendersendsanumberofTCPsegmentsandreceivesallACKsjustbeforethenextRTT(ignorethetimebetweenback-to-backsentsegments).Finally,assumethat15lhand2tsegmentsgotlostduringtheirfirsttransmission.Now,byusingtheaboveinformation,yourtaskistocompletetheblankentriesinthebelowtableuntilallthesegmentsaresentandalltheACKsaresuccessfullyreceived.Ifyouwant,youcanusethechartbelowtoworkoutyoursolutionbeforefillinginthetablebelow.Cong.Win.CHART.Ol234567891011RTTTABLERTTThresholdCongestionWindowSegmentsthataresent04111422,32345678910113. (5points)Matchthetermswiththeirbestcorrespondingdefinitionorconcepts.Jointhemtogetherwithlines.SYN,ACKAlayer4protocolSpanningTreeAlgorithmOneoftheirprimaryjobsinvolvesRFCsrepeaterTechniquestoefficientlyuseIPaddressesIETFThismodellacksasetupandteardownphaseVLSM,CIDRThislayer2technologyhelpspreventbridgeloopsinEthernetLANsandalsointokenringLANsconnectionlessYoumightthislayer2technologyintokenringLANs,butnotinEthernetLANsFull-duplexSomethingyoumightfindinthe3-wayhandshakeUDPAnexampleofawirelinktechnologySourceroutebridgingTheabilitytotalkandlistenatthesametimeOpticalfibercablingThisdevicemovesbitsfromonedatalinknetworktoanotherwithoutinspectingtheframe,scontents4. (total:8points)Cachinganddelays.Considerthenetworksshowninthefigurebelow.Therearetwousermachinesml.aandm2.ainthenetworka.Supposetheuseratml.atypesintheURLb/bigfile.htmintoabrowsertoretrieveaIGbit(1000Mbit)filefromb.www.b.mAuthoritative DNS server for a)(5points)ListthesequenceofDNSandHTTPmessagessent/receivedfrom/byml.aaswellasanyothermessagesthatleave/entertheanetworkthatarenotdirectlysent/receivedbyml.afromthepointthattheURLisenteredintothebrowseruntilthefileiscompletelyreceived.Indicatethesourceanddestinationofeachmessage.YoucanassumethateveryHTTPrequestbyml.aisfirstdirectedtotheHTTPcacheinaandthatthecacheisinitiallyempty,andthatallDNSrequestsareiteratedqueries.b)(3points)Nowassumethatmachinem2.amakesarequesttoexactlythesameURLthatml.amade.ListthesequenceofDNSandHTTPmessagessent/receivedfrom/bym2.aaswellasanyothermessagesthatleave/entertheanetworkthatarenotdirectlysent/receivedbym2.afromthepointthattheURLisenteredintothebrowseruntilthefileiscompletelyreceived.Indicatethesourceanddestinationofeachmessage.Hint:makesureyouconsidercachinghere5. (total:11points)Addressing,andfollowingthedataConsiderthesimplenetworkshownbelow:111.111.Illa)WritedownanIPaddressforallinterfacesatallhostsandroutersinthenetwork.TheIPaddressesforAandEareasgiven.YoushouldassignIPaddressessothatinterfacesonthesamenetworkhavethesamenetwork-partoftheirIPaddress.Indicatethenumberofbitsinthenetwor<-partofthisaddress.BRlCR2Db)Choosephysicaladdresses(LANaddresses)foronlythoseinterfacesonthepathfromAtoE.AEBRlCR2DCantheseaddressesbethesameasinparta)?Why?c) NowfocusontheactionstakenatboththenetworkanddatalinklayersatsenderA,theinterveningrouter,anddestinationEinmovinganIPdatagramfromAtoE:®HowdoA,EandtherouterdeterminetheIPaddressesneededfortheIPdatagram?WhaLspecifically,aretheaddressesintheIPdatagramthatflowsfromAtotherouter?SourceIPDestinationIPWhat,specifically,aretheaddressesintheIPdatagramthatflowsfromtheroutertoE.?SourceIPDestinationIP(3)WhatarethreeotherfieldsfoundinanIPdatagram?HoWdoA,Eandtherouterdeterminethephysical(LAN)addressesneededforthedatalinklayerframe?d) Supposethattherouterinthefigurebelowisreplacedbyabridge.HowwouldtheIPaddresseschangeinthiscase?HoWwouldthephysical(LAN)addresseschangeinthiscase?(3)HowwoulddoesalearningbridgelearnthephysicaladdressesoftheattachedhostsPARTV:(total:6points)Aboutthelabs.ThefollowingtranscriptisamailtransfersessionbetweenhostsAandBusingTCP/IP.Accordingtothesession,answerthetuestions.A: 220umass.edusimplemailtransferservicereadyB: HELOsanfan.eduA: 250umass.govHellosanfan.edu,pleasetomeetyouB: MAILFROM:<aliccsanfan.cdu>A: 250mailacceptedB: RCPTTO:<bobumass.edu>A: 250recipientacceptedB: RCPTTO:<tomumass.edu>A: 550nosuchuserhereB: RCPTTO:<lucyumass.edu>A: 250recipientacceptedB: DATAA: 354startmailinput;endwith<CR><LF>.<CR><LF>B: Date:Sat14June202313:26:31BJ8: From:alicesanfan.cduB:B:B:B:.A: 250OKB: QUITA:221umass.eduserviceclosingtransmissionchannel.Questions:1. Whatisthewholenameofthesender,shost?Whatistheusernameofthesender?2. HowmanyusersdoesthesenderwanttosendtheE-mail?3. Whatisthewholenameofthereceiver,shost?4. WhichuserscanreceivetheE-mail?5. Forreceivingthemail,whatistheportnumberwaitingfortheconnectiononthereceiverhost?6. Whatisthenameofthetransportlayerprotocol?OptionalQuestion(NoPointsforthisexam)：Thisfinalexaminationwas:a.EasierthanIexpectedb.AboutwhatIexpectedc.HarderthanIexpected