2008春夏学期计算机网络基础期末试卷含答案-非final

浙江大学2007–2008学年春夏季学《计算机网络基础》课程期末考试试开课学院：计算机学院，考试形式：闭卷，允许带计算器_考试时间：_08_年_7月_1_日,所需时间：120分钟，任课教 考生 学号 —二三四五六七八注意：请把答案写在第1页、第2页的答题纸对应的题号内，只有答题纸内的答案将作为评一、(10题 得(50题 得三、(21(1).Theoriginaldatagrambreaksinto fragments,thelengthofthefirstfragment’sdatapartisbytes,andthelengthofthelastone’sdatapartisthefirstfragment: ,,,,,thesecondfragment: ,,,,,thelast ,,,,四、(10

(2)

(3)

(4)

(5) 五、(9

一、Pleasechoosetrueorfalseforthefollowingquestions(write√inthetableiftrue,otherwisewrite×)(10points) ephoneisahighbandwidthwirelesssystem.Anotebookcomputerwitha802.11networkadapterconnectingtotheInternetisawirelessandcomputer.Amaycontainuptofivefields,oneofthemissecurity.SLIPandPPPdonotprovideanyformofauthentication.Inadatagramsubnet,therouteischosenonlywhentheconnectionisestablished.In802.11LAN,ifstationXreceivedRTS,butdidnotreceiveCTS,thenXcantransmititsdataandwillnotinterferewithotherstations.ThebasicfunctionofRTPistomultiplexseveralreal-timedatastreamsontoUDPpackets.Thebase64encodingcanbeusedforconvertinganon-ASCIItoanASCII,whichoperatesbybreakingthree8-bitbytesintofour6-bitbytes.PGP(PettyGoodPrivacy)encryptsdatabyusingablockciphercalledAES.Largeamountsofsecretdataarenormallyencryptedusingsecret-key(sessionkey)cryptography,althoughpublic-keycryptograph(suchasRSA),iswidelyusedfortheauthenticationprotocolandforestablishthesessionkey.二、Pleaseselectthebestchoiceforfollowingquestionsandfilltheanswerintothetable(50points)ThePDUforthetransportlayerofTCP/IPisalsocalled Therearetwotypesoftransmissiontechnologythatareinwidespreaduse.TheyareasBroadcastlinksandpoint-to-pointEthernetandEthernetandtokenEnd-to-endlinksandpoint-to-pointWirelessnetworkscanbedividedintothreemaincategories:system BluetoothandBluetoothandwirelessLANsandwireless802.5andWhichofthefollowingstatementsbestdescribesaItconnectsLANsthatareseparatedbyalargegeographicareasuchasseveralItisaprivay-ownednetworkwithinasinglebuildingorItisaprivay-ownednetworkwithinasinglebuildingoruptoafewkilometersinsize.ItcoversaWhichtypeofnetworkdoesFrameRelaybelongscircuitmessagepacketfrequencyFullnameofP2P PeertotoPeopletoProtocoltoInoriginalARPANET,thesubnetwouldconsist puters ==========================physicallayerAsignalconsistsof8discretelevels,itissentoveralow-passnoiselesschannelofbandwidth4kHz,whatistheumachievabledatarate?120002400032000ItcanbeIfadigitalsignalismodulatedandsentoverachannelwhosesignal-to-noiseratiois63:1,anditspassedsignalfrequenciesare2to18KHZ,whatistheumachievabledatarate?96009600019200192000Whichisnotthecomponentoftransmissionsystemusingsignal-modeopticalopticalfibersemiconductorWhatisthecablebetweentwoephoneswitchesthathaveadistanceof4SubscriberlocalInpacketswitching,circuitswitchingandmessageswitching,whichonedoesnotutilizestore-and-forwardtransmissiontechnology?packetcircuitmessagenoneofInpacketswitching,circuitswitchingandmessageswitching,whichonehasthesmallesttransmissiondelayfordataunit?packetcircuitmessagebothmessageswitchingandpacket DatalinklayerAbitstring,101111110111110,needstobetransmittedatthedatalinklayer.Whatisthestringactuallytransmittedafterbitstuffing?A.)10111110101B.)1011111101C.)10111111001D.)Noneofthe -basedflowcontrol,thereceiversendsbackinformationtothesenderitpermissiontosendmoreWhatistheremainderwhendividingx7+x5+1bythegeneratorpolynomialx3+A.)X4+x2+X2+x+X2+X2+AssumethatGo-Back-Nprotocoland3-bitsequencenumberareused,thesendingwindowsizeis5.Afterastationhassenttheframewithsendingsequencenumber6,itreceivesanACKframewithACKsequencenumber4,thenthesendingsequencenumberofthefinalframethatthestationcansendwithinsendingwindow A.)B.)C.)D.)Fortheabovequestion,ifthesendingwindowsizeis3,thenthesendingsequenceofthefinalframe A.)B.)C.)D.)AdatalinkprotocolusesGo-Back-n,and4bitsareusedforsequencenumber,whichisnotallowedassendingwindowsize?18 MAClayerWhenPCF(PointCoordinationFunction)isemployed,usersof802.11useacalled Whichusesthethincoaxial10Base-WhichofthefollowingcanbeasubstitutionforADSLinA.)B.)C.)D.)WhichisnottheresultofabroadcastTheentireLANcapacityisoccupiedbytheseAllthemachinesonalltheinterconnectedLANsarebusyingwithprocessinganddiscardingallthebroadcastframes.ThebandwidthfornormaltrafficisAloopwillbeWhichisthebroadcastaddressofEthernetMACNoneoftheWhichdescriptionisfalseabouttheforwardingprocedureofaIfdestinationandsourceLANsarethesame,discardtheIfthedestinationandsourceLANsaredifferent,forwardtheEveryentryofthebridge’sforwardingtablewillneverbeIfthedestinationLANisunknown,useWhichdevicewillextendthesizeofLAN’scollision networklayerWhichofthefollowingstatementsaboutIPv4headerfieldsisIHLfieldlshowlongtheheaderTheTimetolivefieldisacounterusedtolimitpacketTheProtocolfieldlsnetworklayerwhichupper-layerprotocolprocesstogivedatagramto.TheTotallengthfieldindicatesthepayloadlengthoftheWhichisnottheprivateaddressthatwillnotappearinInternetA.)B.)C.)D.)Thesubnetmaskis48.Howmanyhostsareavailableinthis628WhichofthefollowingstatementsaboutdefaultrouteisInroutetable,adefaultrouteisanentrywiththedestinationnetworkandsubnetmask.Inroutetable,adefaultrouteisanentrywiththedestinationnetworkandsubnetmask55.Ifdefaultrouteexists,itwillbefirstselectedandDefaultrouteprovidestheshortestWhichoneisnotapartoflink-stateroutingArouterdiscoversitsneighborsandlearntheirnetworkArouterexchangesroutetablewithitsAroutermeasuresthedelayorcosttoeachofitsArouterconstructsapacketlingallithasjustTheproblemofrunningoutofIPaddressesisnotatheoreticalproblemthatmightoccuratsomepointinthedistantfuture.SomepeoplefeltthataquickfixwasneededfortheshorttermundercurrentIPv4environment.Thisquickfixcameintheformof WhichisanillegalIPV6A.)B.)3400::4443:89AB:C.)3400:0:0:C0E4:0:4443:89AB:D.)::3400:89AB: transportlayerTwo-armyproblemlsus Three-wayhandshakeisneededtoestablishaDesigningaperfectprotocoltocloseaconnectionisextremelyThree-wayhandshakeisneededtocloseaTwo-wayhandshakeisneededtocloseaTimestampisused Whichprotocoldoesnotmatchitswellknown WhichprotocolusesIfthecongestionwindowsizeis30KB,andthereceivewindowsizeis50KB,whatistheumbytestheTCPentitycantransmitbeforeACKcomesback? applicationlayerWhichoneisnotalegalresourcerecordinDNS starboss RedhatLinux Whichoneisnotacommonprotocol(orscheme)usedinWhichonerepresentsacorrectHTMLtagfor<form /cgi- <form /cgi-bin/scpu” <form /cgi- method=post<form /cgi- method=push-sidedynamicwebpagegenerationmayusefollowing:JavaScript,Javaapplet,Activexcontrol.Whichofthefollowingstatementsisincorrect?JavaScriptprogramshavethebestportabilityamongJavaScriptprogramsareeasiertoJavaappletsexecuteActiveXcontrolsrunfasterofWhenauserclicksonahyperlink,http /lib/index.html,thebrowsercarriesoutaseriesofstepsinordertofetchthepagepointedto.Whichoneisnotinthesesteps?ThebrowserdeterminestheThebrowserasksDNSfortheIPaddressThebrowsersendsaUDPrequestaskingforfileThebrowserdisysallthetextinAmaycontainfivefields,Whichoneisnotinthese fieldwhichindicatesthe Thepathfieldthatidentifieswhichpartsoftheserver’sfiletreemayuse Theexpirefieldthatspecifieswhen TheprotocolfieldthatspecifieswhatprotocolisCommonGatewayInterface(CGI)isastandardizedinterfacetoallowWebServertotalktoback-endprogramsandscripts,thisWebServersends pagestobrowser. networksecurityThepurpose istopreventadversaryfrommodifyingoralteringIntegrity eachletterorgroupoflettersisrecedbyanotherletterorgroupofletterstodisguiseit.TranspositionsubstitutionSHA-isbasedonGaloisfieldtheory,itusessubstitution,permutations,andmultipleroundsofcalculations.TheDiffie-mankeyexchangeprotocolallowstwostrangerstoestablishasharedsecretkey;however,itcanbedefeatedby.bucketbrigadereflectiondenialofattackofelectroniccodebookVariousschemeshavebeendevisedfordigitalsignatures,usingbothsymmetric-key -keyone三、(21pointsInaTCP/IPnetwork,anoriginalIPdatagramcontains1500bytesofdata(i.e.payload)and36bytesofheader.Whenitpassesthrougharouterwiththeumdatagramlength(header+data)of420bytes,itbreaksintomultiplefragments.Intheformat(headerlength,totallength,Identification,DF,MF,offset),thevaluesoforiginaldatagram’sheaderfieldsare(9,1536,13762,0,0,0).Theoriginaldatagrambreaksinto fragments,thelengthofthefirstfragment’sdatapartisbytes,andthelengthofthelastone’sdatapartisPleasefillthesefragment’sheaderfieldvalueswiththe(headerlength,totallength,Identification,DF,MF,offset)infollowingblanks:thefirstfragment: ,,,,,thesecond thelast answer:(1).Theoriginaldatagrambreaksinto4fragments,thelengthofthefirstfragment’sdatapartis384bytes,andthelengthofthelastone’sdatapartis348(2).Pleasefillthesefragment’sheaderfieldvaluesina(headerlength,totallength,Identification,DF,MF,offset)infollowing1# 2# 4# 四、(10points)ConsiderbuildingaCSMA/CDnetworkrunningat100Mbpsovera800-mcablewithoutrepeater.Thesignalspeedinthecableis200,000km/sec,andstationAandBarelocatedinthetwoendofthecable.Pleasefillvaluesinfollowingblanks.Thetimetotransmit1byteisnotedasT,T=metersalongthecableinintervalT.

s,aframecan

TheroundtriptimebetweenAandBis(4)

s,theminimumframesizeshouldIfthedata es1Gbpsandthecable es200meters,theframesizeshouldbe(5)answer(1).Thetimetotransmit1byteisnotedasT,T=_0.08_s,aframecanrun16metersalongthecableinintervalT.TheroundtriptimebetweenAandB100

s,theminimumframesizeshouldIfthedata es1Gbpsandthecable es200meters,theframesizeshouldbe250 (9points)HDLCandTCParedifferentprotocols,somefeaturesarediscussedasfollows,pleasechooseappropriatewordfromtheoptionalwordslistandfillitintheThesendingsequencenumberofHDLCPDUsincrementsby100when100 aresent,whilethesendingsequencenumberofTCPPDUsincrementsby100when aresent.HDLC’ssendingwindowusesa value;TCP’ssendingwi