华南理工软件学院2015期末考试-计算机网络B卷

《ComputerNetworks》试卷(B)第5页共9页姓名学号学院姓名学号学院专业座位号(密封线内不答题)……………………密………………封………线……线………_____________________…华南理工大学期末考试《ComputerNetworks》试卷(B)注意事项：1.考前请将密封线内填写清楚；2.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)；3．考试形式：闭卷；4.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)NO.123456789101112131415solutionSupposeHostAwantstosendafiletoHostB.ThepathfromHostAtoHostBhasthreelinks,theirratesR1=500kbps,R2=250kbpsA.500kbpsB.1MbpsC.250kbpsD.1.75MbpsThetransferofawebdocumentfromonehosttoanotheris:()loss-intolerantandtimeinsensitiveloss-tolerantandtimesensitiveloss-intolerantandtimesensitivenoneoftheaboveEthernetinterfaceaddresses()A.areassignedatmanufacturingtime.B.areassignedmanuallyorbyDNSC.aregeneratedrandomlyandcheckedforuniquenessbybroadcastingamessageD.sharethesamehighorderbits,whichdeterminethenetworkorsubnetinaninternetwork.BasedonTCP/IParchitecture,whichofthefollowingprotocolbelongstodata-linklayer?() A.HTTPB.IPC.UDPD.PPPTwoimportantreasonsthattheInternetisorganizedasahierarchyofnetworksforthepurposesofroutingare()A.LeastcostandmaximumfreecircuitavailabilityB.MessagecomplexityandspeedofconvergenceC.ScaleandadministrativeautonomyD.LinkcostchangesandlinkfailureWithanexteriorroutingprotocol,whichofthefollowingissuesgenerallydominatetheroutingdecisions?()GeographicaldistancebetweenAS’sPolicyNumberofAS’straversedCurrentcongestionlevelsintheAS’sWhichrangeofportnumberarereservedforservicesthatarecommonlyusedbyapplicationsthatrunonserves?()A.0to255.B.0to1023.C.1024to49151.D.49152to65535.WhichinformationiscontainedintheheaderofNetworkLayertohelpdatadelivery?()A.portnumberB.DevicephysicaladdressC.Destinationhost’sIPaddressD.VirtualconnectionidentifierIninternetcommunication,IPdatagramwillgothroughthesourcehostandrouterstoreachthedestinationhost,usually()A.bothsourcehostandroutersallknowthecompletepathtothedestinationhostthatwillbereachedbyIPdatagram.B.sourcehostknowsthecompletepathtodestinationhostthatwillbereachedbyIPdatagram,butnonetheintermediaterouters.C.theintermediateroutersknowthecompletepathtodestinationhostthatwillbereachedbyIPdatagram,butnonethesourcehost.D.neithersourcehostnortheintermediateroutersknowthecompletepathtodestinationSupposeHostAsends4TCPsegmentsbacktoHostBoveraTCPconnection.Thefirstsegmenthassequencenumber56;thesecondhassequencenumber216;thethirdhassequence296;thefourthhassequencenumber346with40byteofdatainit.(5scores)HowmuchbyteofdataareinthethirdTCPsegment?SupposethatthefirstandthefourthsegmentarriveatBinturn,butthesecondandthethirdsegmentsarelost.WhatwillbetheacknowledgmentnumberrespectivelythatHostBsendstoHostAforeacharrivingsegment?WhenHostBreceivesthesecondsegmentandthethirdsegmentre-sendingbyHostAinturn,whatwillbetheacknowledgmentnumberthatHostBsendstoHostAforeacharrivingsegment.Considerarouterthatinterconnectsthreesubnets:Subnet1,Subnet2,andSubnet3.Supposealloftheinterfacesineachofthesethreesubnetsarerequiredtobelongto/24.AlsosupposethatSubnet1isrequiredtosupportatleast20interfaces,Subnet2istosupportatleast60interfaces,andSubnet3istosupportatleast90interfaces.Providethreenetworkaddresses(offorma.b.c.d/x)thatsatisfytheseconstraints.(9scores)ComprehensiveQuestions(26scores)ConsideranIPdatagrambeingsentfromAtoB.GivetheserviceanddestinationEthernetaddressaswellasthesourceanddestinationaddressoftheIPdatagramencapsulatedwithintheEthernetatpoints(1),(2),(3).AssumethefollowinggraphshowsthebehaviorofaTCPcongestioncontrolanswereachquestionwithashortdiscussionjustifyingyouranswer.IdentitytheintervalsoftimewhenTCPshowstartisoperating.IdentitytheintervalsoftimewhenTCPcongestionavoidanceisoperating.After14thtransmissionroundissegmentlossdetectedbytripleduplicateACKorbyatimeout?AndwhichversionofTCPprotocol(RenoorTahoe)isusedbaseonthisinformation?Duringwhattransmissionroundisthe50thsegmentsent?Assumingapacketlossisdetectedafterthe23rdroundbyreceiptofatripleduplicateACKs,whatwillbethevalueof