华南理工软件学院2015期末考试-计算机网络B卷

《ComputerNetworks《ComputerNetworks》试卷（B）第页共9页姓姓《ComputerNetworks》试卷(B)第1页共9页注意事项：.业—专NO.123注意事项：.业—专NO.123456789101112131415solution题答不内线封密（(1)SupposeHostAwantstosendafiletoHostB.ThepathfromHostAtoHostBhasthreelinks,theirrates耳：=E二：久=：;方，总：=IE：汽二芦,and耳：=1.Assumingnoothertrafficinthenetwork,whatisthethroughputforthefiletransfer?()A.£护B.-KC.15：S:庐D../5：i：:茁(2)Thetransferofawebdocumentfromonehosttoanotheris:()A.B.loss-intolerantand廿meinsensitiveloss-tolerantand廿mesensitive诚信应考,考试作弊将带来严重后果！华南理工大学期末考试《ComputerNetworks》试卷(B)考前请将密封线内填写清楚；所有答案请答在答题纸上（注：选择题答案请填入题目前面的表格中）;考试形式：闭卷；本试卷共5大题，满分100分，考试时间120分钟。题号12345总分得分评卷人Selectthecorrectchoice.(30scores,everyoneis2scores)C.D.noneoftheaboveC.D.noneoftheaboveloss-intolerantand廿mesensitiveEthernetinterfaceaddresses()areassignedatmanufacturingtime.B.areassignedmanuallyorbyDNSC.aregeneratedrandomlyandcheckedforuniquenessbybroadcastingamessageD.sharethesamehighorderbits,whichdeterminethenetworkorsubnetinaninternetwork.BasedonTCP/IParchitecture,whichofthefollowingprotocolbelongstodata-linklayer?

A.HTTPB.IPC.UDPD.PPPA.HTTPB.IPC.UDPD.PPPTwoimportantreasonsthattheInternetisorganizedasahierarchyofnetworksforthepurposesofroutingare()LeastcostandmaximumfreecircuitavailabilityMessagecomplexityandspeedofconvergenceScaleandadministrativeautonomyLinkcostchangesandlinkfailureWithanexteriorroutingprotocol,whichofthefollowingissuesgenerallydominatetheroutingdecisions?()GeographicaldistancebetweenAS'sPolicyNumberofAS'straversedCurrentcongestionlevelsintheAS'sWhichrangeofportnumberarereservedforservicesthatarecommonlyusedbyapplicationsthatrunonserves?()0to255.B.0to1023.C.1024to49151.D.49152to65535.WhichinformationiscontainedintheheaderofNetworkLayertohelpdatadelivery?()portnumberB.DevicephysicaladdressC.Destinationhost'sIPaddressD.VirtualconnectionidentifierIninternetcommunication,IPdatagramwillgothroughthesourcehostandrouterstoreachthedestinationhost,usually()bothsourcehostandroutersallknowthecompletepathtothedestinationhostthatwillbereachedbyIPdatagram.sourcehostknowsthecompletepathtodestinationhostthatwillbereachedbyIPdatagram,butnonetheintermediaterouters.theintermediateroutersknowthecompletepathtodestinationhostthatwillbereachedbyIPdatagram,butnonethesourcehost.neithersourcehostnortheintermediateroutersknowthecompletepathtodestination

hostthatwillbereachedbyIPdatagram.WhichcombinationofnetworkidandsubnetmaskcorrectlyidentifiesallIPaddressformthrough55?(2424B.B.C.C.D.D.92WhathappenswhenanodeonanEthernetnetworkiscreatingaframeanditdoesnothavethedestinationMACaddress?(A.Thenodedropstheframe.Thenodesendsoutalayer3broadcastmessages.C.Thenodesendsamessagedirectlytotherouterfortheaddress.D.ThenodesendsoutanARPrequestwiththedestinationIPaddress.Supposeanapplicationgenerateschunksof120bytesofdataeverysecond,andeachchunkgetsencapsulatedinaTCPsegmentandthenanIPdatagram(nooptionsfields).Whatpercentageofeachdatagramwillcontainapplicationdata?(A.80%75%60%A.80%75%60%25%WhichstatementistrueabouttheCSMA/CDaccessmethodthatisusedinEthernet?()A.whenadevicehearsacarriersignalandtransmits,acollisioncannotoccur.Ajammingsignalcausesonlydevicesthatcausedthecollisiontoexecuteabackoffalgorithm.Allnetworkdevicesmustlistenbeforetransmitting.Devicesinvolvedinacollisiongetprioritytotransmitafterthebackoffperiod.IntheEthernettwo-layerswitches,howistheforwardingtableestablished?()A.ManualconfigurationB.Self-learningRoutingalgorithmD.DestinationaddresslearningConsidersendinga999bytedatagramintoalinkthathasanMTUof500bytes,()A.2fragmentsarecreatedwithoffsetfieldvalue0,500,respectively3fragmentsarecreatedwithoffsetfieldvalue0,480,960,respectively3fragmentsarecreatedwithoffsetfieldvalue0,60,120,respectivelyNoneoftheseaboveFilltheblank.(10scores,everyblankis1score)TOC\o"1-5"\h\zThemostimportantkindsofdelayateachnodealongthepathisnodalprocessingdelay,queuingdelay,,.Thetaskofthedatalinklayerisprovidingdatatransmissionservicesbetween;Thetaskofthenetworklayerisprovidingdatatransmissionservicesbetween;andthetaskoftransportlayerisprovidingdatatransmissionservicesbetween.IntheTCP,connectionestablishmentoftransportlayerusemethodof.TheheadofIPdatagramhasafield,whenthevalueofthefieldis0,thedatagramtransmittedwillbediscarded.TheroutingprotocolOSPFisrecommendedforaintraAS,whichisbasedonroutingalgorithm,andtheroutingprotocolBGPisrecommendedforinterAS.TheroutingprotocolRIPisbasedonroutingalgorithm.RIPusecountasacostmetric;thatis,eachlinkhasacostof1.Judgethefollowingquestionsastrueorfalse.(10scores,everyoneis1scores)NO.12345678910Solution(TorF)TheTracerouteprograminthesourcehostwillsentaseriesofICMPmessagetodeterminetheroutebetweensourcehostanddestinationhost.Attheheartofrdt3.0'sperformanceproblemisthefactthatitisastop-and-waitprotocol.WhenauserrequestaWebpagethatconsistsofsometextandtwoimages.Forthispage,theclientwillsendonerequestmessageandreceivethreeresponsemessage.UDPisthepreferredoverTCPfortransferringareal-timevoiceoverIPnetworks.Withawindowsizeof1,SR,GBNarefunctionallyequivalent.Whenusingdistaneevectorroutealgorithm,thecompletenetworktopologyinformationmustbeknownbyarouter.Emailsaredeliveredtoreceiver'sserverusingPOP3protocol.CollisionswillnotoccurunderCSMA/CDMACprotocol.WhenaTCPsegmentarrivestoahost,thesockettowhichthesegmentisdirecteddependsonthedestinationportnumberandthedestinationIPaddressofthedatagramencapsulatedthesegment.IfanAutonomoussystemlearnsof5differentroutestoadestinationprefixitwillannounceall5routestoitsneighbors.Answerthefollowingquestionsbriefly・(24scores)Whatarethe5layersintheInternetprotocolstack?Whataretheprincipalresponsibilitiesofeachoftheselayers?(5scores)Themessage二=_=istransmittedusingtheCRCmethoddescribedinclassusingthegeneratorpolynomial二=二：二二二l.Pleaseanswerthefollowingquestions.(5scores)SupposeHostAsends4TCPsegmentsbacktoHostBoveraTCPconnection.Thefirstsegmenthassequencenumber56;thesecondhassequencenumber216;thethirdhassequence296;thefourthhassequencenumber346with40byteofdatainit.(5scores)HowmuchbyteofdataareinthethirdTCPsegment?SupposethatthefirstandthefourthsegmentarriveatBinturn,butthesecondandthethirdsegmentsarelost.WhatwillbetheacknowledgmentnumberrespectivelythatHostBsendstoHostAforeacharrivingsegment?WhenHostBreceivesthesecondsegmentandthethirdsegmentre-sendingbyHostAinturn,whatwillbetheacknowledgmentnumberthatHostBsendstoHostAforeacharrivingsegment.Considerarouterthatinterconnectsthreesubnets:Subnet1,Subnet2,andSubnet3.Supposealloftheinterfacesineachofthesethreesubnetsarerequiredtobelongto/24.AlsosupposethatSubnet1isrequiredtosupportatleast20interfaces,Subnet2istosupportatleast60interfaces,andSubnet3istosupportat

least90interfaces.Providethreenetworkaddresses(offorma.b.c.d/x)thatsatisfytheseconstraints.(9scores)ComprehensiveQuestions(26scores)ConsideranIPdatagrambeingsentfromAtoB.HF-E-Z-01-DE-73-A5C46-3^-38-9C-9E-E6K：.119.169.51HF-E-Z-01-DE-73-A5C46-3^-38-9C-9E-E6K：.119.169.51GivetheserviceanddestinationEthernetaddressaswellasthesourceanddestinationaddressoftheIPdatagramencapsulatedwithintheEthernetatpoints(1)