计算机网络英文题库附答案chapter3解析.docx
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计算机网络英文题库附答案chapter3解析.docx
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计算机网络英文题库附答案chapter3解析
计算机网络英文题库
(附答案)chapter3解
析
-CAL-FENGHAI.-(YICAI)-CompanyOne1
Chapter3TransportLayer
1.Atransport-layerprotocolprovidesforlogicalcommunicationbetween・
AApplicationprocesses
BHosts
CRouters
DEndsystems
2.Transport-layerprotocolsrunin・
AServers
BClients
CRouters
DEndsystems
3.Intransportlayer,thesendsidebreaksapplicationmessagesinto,passesto
networklayer.
AFrames
BSegments
CData-grams
Dbitstreams
4.Servicesprovidedbytransportlayerinelude・
AHTTPandFTP
BTCPandIP
CTCPandUDP
DSMTP
5.WhichofthefollowingservicesisnotprovidedbyTCP
ADelayguaranteesandbandwidthguarantees
BReliabledatatransfersandflowcontrols
CCongestioncontrols
DIn-orderdatatransfers
6.Thesetwominimaltransport-layerservices——and——aretheonlytwo
servicesthatUDPprovides!
Aprocess-to-processdatadelivery,errorchecking
Bcongestioncontrol,reliabledatatransfer
Cflowcontrol,congestioncontrol
DIn-orderdatatransfer,errorchecking
7.Portnumber'sscopeisto・
A0,1023
B0.65535
C0,127
D0,255
8.Theportnumbersrangingfromtoarecalledwell-knownportnumber
andarerestricted・
A0,1023
B0,65535
C0,127
D0,255
9.UDPsocketidentifiedbytwocomponents,theyare・
AsourceIPaddressesandsourceportnumbers
BsourceIPaddressesanddestinationIPaddresses
CdestinationIPaddressanddestinationportnumbers
Ddestinationportnumbersandsourceportnumbers
10.TCPsocketidentifiedbya(an)・
A1-tuple
B2-tuple
C3-tuple
D4-tuple
11.WhichofthefollowingapplicationsnormallyusesUDPservices
ASMTP
BStreamingmultimedia
CFTP
DHTTP
12.Reliabledatatransferprotocoloveraperfectlyreliablechannelis・
Ardt1.0Brdt2.0Crdt3.0Drdt2.1
13.Reliabledatatransferprotocoloverachannelwithbiterrorsandpacketlossesis
Ardt1.0Brdt2.0Crdt3.0Drdt2.1
14.WhichofHiefollowingaboutreliabledatatransferoverachannelwithbiterrorsisnotcorrect?
ARDT2.0:
assumingACKandNAKwillnotbecornipted
BRDT2.1:
assumingACKandNAKcanbecorrupted
CRDT2.2:
onlyuseACK-s
DRDT2.2:
usebothACK-sandNAK-s
15.Whichofthefollowingprotocolsisnotpipeliningprotocols?
ATCPBrdt3.0
CGO-BACK-NDselectiverepeat
16.WhichofthefollowingisnotcorrectaboutGBNprotocol?
AOnlyusingACK-s
BUsingcumulativeACK-s
CReceiverdiscardsallout-of-orderpackets
DItisnotpipelinedprotocol
17.WhichofthefollowingisnotcorrectaboutSRprotocol?
Areceiverindividuallyacknowledgesallcorrectlyreceivedpackets
BsenderonlyresendspacketsforwhichACKnotreceived
CItlimitssequencenumberofsentbutun-ACK-edpackets
DItisnotapipelinedprotocol
18.WhichofthefollowingaboutTCPconnectionisnotcorrect
AItisabroadcastconnection
BItisapoint-to-pointconnection
CItisapipelinedconnection
DItisafullduplexconnection
19.TheSYNsegmentisusedfor・
ATCPconnectionsetup
BTCPflowcontrol
CTCPcongestioncontrol
DClosingaTCPconnection
20.TheFINsegmentisusedfor・
ATCPconnectionsetup
BTCPflowcontrol
CTCPcongestioncontrol
DClosingaTCPconnection
21・HowdoesTCPsenderperceivecongestion
AThroughatimeoutevent
BThroughareceivingduplicateACK-sevent
CBothAandB
DEitherAorB
22.Extendinghost-to-hostdeliverytoprocess-to-processdeliveryiscalledtransportlayerand_.
Amultiplexingandde-multiplexing
Bstoringandforwarding
Cforwardingandfiltering
Dswitchingandrouting
23.UDPisasendeewhileTCPisaconnection-orientedservice・
AConnectionless
BReliable
CConnection-oriented
DIn-order
24.TheUDPheaderhasonlyfourfields,theyare・
ASourceportnumbei;destinationportnumber,lengthandchecksum
BSourceportnumber,destinationportnumber,sourceIPanddestinationIP
CsourceIP,destinationIP,sourceMACaddressanddestinationMACaddress
DsourceIP,destinationIP,sequencenumberandACKsequencenumber
25.Therearetwo16七itintegers:
1110011001100110,1101010101010101.Their
checksumis・
010*********
B1011101110111100
C111111*********1
D1000000000000000
26.Themaximumamountofdatathatcanbegrabbedandplacedinasegmentis
limitedbythe・
AMaximumsegmentsize(MSS)
BMTU
CChecksum
DSequencenumber
27.TheMSSistypicallysetbyfirstdeterminingthelengthofthelargestlinklayerframethatcanbesentbythelocalsendinghost——theso-called・
AMaximumtransmissionunit(MTU)
BMSS
CChecksum
DSequencenumber
2&AFilesizeof500,000bytes5MSSequalslOOObytes.WhenwewanttotransmitthisfilewithTCP,thesequencenumberofthefirstsegmentis0,andthesequencenumberofthesecondsegmentis・
A1000
B999
C1001
D500000
29.BecauseTCPonlyacknowledgesbytesuptothefirstmissingbyteinthe
stream,TCPissaidtoprovide・
ACumulativeacknowledgements
BSelectiveacknowledgements
C3duplicateACKs
DpositiveACKs
30.Provideda=0・125,currentvalueofEstimated-RTTis0.4s,Saniple-RTTis0.8s,
thenthenewvalueofEstimated-RTTiss.
A0.45
B0.6
C0.7
D0.8
31.ProvidedRcvBuffer=20,LastByteRcvd=20,LastByteRead=15,then
RevWindow二・
A14
B15
C16
D10
32.TCPservicedoesnotprovide・
AReliabledatatransferBFlowcontrol
CDelayguaranteeDCongestioncontrol
33.TherearetwostatesinTCPcongestioncontrol,whichare・
Aslowstartandcongestionavoidance
Bsafestartandcongestionavoidance
Cslowstartandcongestionabandon
Dsafestartandcongestionabandon
34.Thetransport-layerprotocolprovideslogicalcommunicationbetween,and
thenetwork-layerprotocolprovideslogicalcommunication・
Ahosts,processes
Bprocesses,hosts
Cthreads,processes
Dprocesses,threads
35.ToimplementthemulticastservicestheInternetemploystheprotocol.
AFTPBTCPCIGMPDUDP
36.Ifanapplicationdeveloperchoosesprotocol,thentheapplicationprocessis
almostdirectlytalkingwithIP.
AHTTP
BRIP
CCSMA/CD
DUDP
37.maintainsconnection-stateintheendsystems.Thisconnectionstate
includesreceiveandsendbuffers,congestion-controlparameters,andsequenceandacknowledgmentnumberparameters・
AUDPBTCPCDNSDHTTP
38.ThehostthatinitiatesthesessionintheInternetislabeledas.
AserverBuseragentCclientDrouter
39.WithTCPthereisnobetweensendingandreceivingtransport-layer
entities・
AflowcontrolBhandshaking
C・congestioncontrolDVCsetup
40.TlieInternet'sservicehelpspreventtheIntenietfi*omenteringastateof
gridlock・
AdatagramBcongestioncontrol
CslidingwindowDtimeoutevent
41・Connectionsetupatthetransportlayerinvolves・
AserverBonlythetwoendsystems
CclientDrouter
42.Alayerprotocolprovidesforlogicalcommunicationbetweenapplications.
Atransport
Bapplication
Cnetworking
DMAC
43.Instaticcongestionwindow,ifitsatisfiesW*S/R>RTT+S/R,theLatencyis
AW*S/R-(RTT+S/R)
B2RTT+O/R
C2RTT+O/R+(k-1)[W*S/R-(RTT+S/R)]
D2RTT+S/R
44.Thereceivesideoftransportlayerreassemblessegmentsintomessages,passestolayer.
AApplication
BNetworking
CPhysical
DMAC
45.Inthefollowingfouroptions,whichoneiscorrect?
AThevariationsintheSampIeRTTaresmoothedoutinthecomputationoftheEstimatedRTT
BThetimeoutshouldbelessthantheconnection'sRTT
CSupposethatthelastSampIeRTTinaTCPconnectionisequalto1sec.ThenthecurrentvalueofTimeoutintervalwillnecessarilybe>lsec
DSupposethatthelastSampIeRTTinaTCPconnectionisequalto1sec.ThenthecurrentvalueofTimeoutintervalwillnecessarilybe 46.TheportnumberusedbyHTTPis. A80 B25 C110 D53 47.TheportnumberusedbySMTPis. A80 B25 C110 D53 4&Theportnumberusedbypop3is A80 B25 C110 D53 49.TheportnumberusedbyDNSis A80 B25 C110 D53 50.TheportnumberusedbyFTPis. A20and21 B20 C21 D53 51.AUDPsocketidentifiedbyatuple(s). A2 B4 C1 D3 52.ATCPsocketidentifiedbyatuple(s). A2 B4 C1 D3 53.ATCPsocketdoesnotinclude. ASourceMACaddress BSourceportnumber CDestinationIPaddress DDestinationportnumber 54.WhichoffollowingaboutUDPisnotcorrect. AItisareliabledatatransferprotocol BItisconnectionless CnohandshakingbetweenUDPsender,receiver Ditisabesteffortserviceprotocol 55.DNSusesservice・ ATCP BUDP CBothTCPandUDP DNoneofabove 56.WhichoffollowingaboutUDPiscorrect AFinerapplication-levelcontroloverwhatdataissent,andwhen BNoconnectionestablishment(whichcanadddelay),sonodelayforestablisha connection CNoconnectionstate(so,UDPcantypicallysupportmanyactiveclients) DLargepacketheaderoverhead(16・B) 57.Streamingmediausesaservicenormally・ ATCP BUDP CBothTCPandUDP DNoneofabove 58.TheUDPheaderhasonlyfields. A2 B4 C1 D3 59.WhichofthefollowingdoesnotincludedinUDPheader. ASourceportnumber BDestinationportnumber CChecksum DSequencenumber 60.WhichofHiefollowingisnotapipeliningprotocol. ARdtl.O BGo-Back-N CSelectiverepeat DTCP 61.InthefollowingfourdescriptionsaboutMSSandMTU,whichoneisnotcorrect ATheMSSisthemaximumamountofapplication-layerdatainthesegment BTheMSSisthemaximumsizeoftheTCPsegmentincludingheaders CTheMSSistypicallysetbyMTU DTheMTUmeansthelargestlink-layerframe 62.Thejobofgatheringdatachunks,encapsulatingeachdatachunkwithheader informationtocreatesegmentsandpassingHiesegmentstothenetworkiscalled Amultiplexing Bde-multiplexing Cforwarding Drouting 63.Inthefollowingfourdescrip
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