计算机网络英文试题库附答案chapter3解析.docx

计算机网络英文试题库附答案chapter3解析.docx

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计算机网络英文试题库附答案chapter3解析

Chapter3TransportLayer

1.Atransport-layerprotocolprovidesforlogicalcommunicationbetween____.

AApplicationprocesses

BHosts

CRouters

DEndsystems

2.Transport-layerprotocolsrunin____.

AServers

BClients

CRouters

DEndsystems

3.Intransportlayer,thesendsidebreaksapplicationmessagesinto____,passestonetworklayer.

AFrames

BSegments

CData-grams

Dbitstreams

4.Servicesprovidedbytransportlayerinclude____.

AHTTPandFTP

BTCPandIP

CTCPandUDP

DSMTP

5.WhichofthefollowingservicesisnotprovidedbyTCP?

ADelayguaranteesandbandwidthguarantees

BReliabledatatransfersandflowcontrols

CCongestioncontrols

DIn-orderdatatransfers

6.Thesetwominimaltransport-layerservices----____and____----aretheonlytwoservicesthatUDPprovides!

Aprocess-to-processdatadelivery,errorchecking

Bcongestioncontrol,reliabledatatransfer

Cflowcontrol,congestioncontrol

DIn-orderdatatransfer,errorchecking

7.Portnumber’sscopeis____to____.

A0,1023

B0,65535

C0,127

D0,255

8.Theportnumbersrangingfrom____to____arecalledwell-knownportnumberandarerestricted.

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. Reliable data transfer protocol over a perfectly reliable channel is____.  

A  rdt1.0   B  rdt2.0 C  rdt3.0   D  rdt2.1 

13. Reliable data transfer protocol over a channel with bit errors and packet losses is ____. 

 A  rdt1.0  B  rdt2.0 C  rdt3.0   D  rdt2.1 

14. Which of the following about reliable data transfer over a channel with bit errors is not correct?

A  RDT2.0:

 assuming ACK and NAK will not be corrupted 

B  RDT2.1:

 assuming ACK and NAK can be corrupted 

C  RDT2.2:

 only use ACK-s 

D  RDT2.2:

 use both ACK-s and NAK-s 

15. Which of the following protocols is not pipelining protocols?

 A  TCP B  rdt3.0 

C  GO-BACK-N D  selective repeat 

16. Which of the following is not correct about GBN protocol?

A  Only using ACK-s 

B  Using cumulative ACK-s  

C  Receiver discards all out-of-order packets 

D  It is not pipelined protocol 

17. Which of the following is not correct about SR protocol?

A  receiver individually acknowledges all correctly received packets 

B  sender only resends packets for which ACK not received 

C  It limits sequence number of sent but un-ACK-ed packets 

D  It is not a pipelined protocol

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-processdeliveryiscalledtransport-layer____and.

Amultiplexingandde-multiplexing

Bstoringandforwarding

Cforwardingandfiltering

Dswitchingandrouting

23.UDPisa____servicewhileTCPisaconnection-orientedservice.

AConnectionless

BReliable

CConnection-oriented

DIn-order

24.TheUDPheaderhasonlyfourfields,theyare____.

ASourceportnumber,destinationportnumber,lengthandchecksum

BSourceportnumber,destinationportnumber,sourceIPanddestinationIP

CsourceIP,destinationIP,sourceMACaddressanddestinationMACaddress

DsourceIP,destinationIP,sequencenumberandACKsequencenumber

25.Therearetwo16-bitintegers:

1110011001100110,1101010101010101.Theirchecksumis____.

A00011

B11100

C11111

D00000

26.Themaximumamountofdatathatcanbegrabbedandplacedinasegmentislimitedbythe____.

AMaximumsegmentsize（MSS）

BMTU

CChecksum

DSequencenumber

27.TheMSSistypicallysetbyfirstdeterminingthelengthofthelargestlink-layerframethatcanbesentbythelocalsendinghost----theso-called____.

AMaximumtransmissionunit（MTU）

BMSS

CChecksum

DSequencenumber

28.AFilesizeof500,000bytes,MSSequals1000bytes.WhenwewanttotransmitthisfilewithTCP,thesequencenumberofthefirstsegmentis0,andthesequencenumberofthesecondsegmentis____.

A1000

B999

C1001

D500000

29.BecauseTCPonlyacknowledgesbytesuptothefirstmissingbyteinthestream,TCPissaidtoprovide____.

ACumulativeacknowledgements

BSelectiveacknowledgements

C3duplicateACKs

DpositiveACKs

30.Providedα=0.125,currentvalueofEstimated-RTTis0.4s,Sample-RTTis0.8s,thenthenewvalueofEstimated-RTTis____s.

A0.45

B0.6

C0.7

D0.8

31.ProvidedRcvBuffer=20,LastByteRcvd=20,LastByteRead=15,thenRcvWindow=____.

A14

B15

C16

D10

32.TCPservicedoesnotprovide____.

AReliabledatatransferBFlowcontrol

CDelayguaranteeDCongestioncontrol

33.TherearetwostatesinTCPcongestioncontrol,whichare____.

Aslowstartandcongestionavoidance

Bsafestartandcongestionavoidance

Cslowstartandcongestionabandon

Dsafestartandcongestionabandon

34.Thetransport-layerprotocolprovideslogicalcommunicationbetween____,andthenetwork-layerprotocolprovideslogicalcommunication____.

Ahosts,processes

Bprocesses,hosts

Cthreads,processes

Dprocesses,threads

35. To implement the multicast services the Internet employs the ____ protocol.  

A  FTP   B  TCP   C  IGMP  D  UDP 

36.Ifanapplicationdeveloperchooses____protocol,thentheapplicationprocessisalmostdirectlytalkingwithIP.

AHTTP

BRIP

CCSMA/CD

DUDP

37.____maintainsconnection-stateintheendsystems.Thisconnectionstateincludesreceiveandsendbuffers,congestion-controlparameters,andsequenceandacknowledgmentnumberparameters.

AUDPBTCPCDNSDHTTP

38.ThehostthatinitiatesthesessionintheInternetislabeledas____.

AserverBuseragentCclientDrouter

39.WithTCPthereisno_____betweensendingandreceivingtransport-layerentities.

AflowcontrolBhandshaking

C.congestioncontrolDVCsetup

40.TheInternet’s____servicehelpspreventtheInternetfromenteringastateofgridlock.

AdatagramBcongestioncontrol

CslidingwindowDtimeoutevent

41.Connectionsetupatthetransportlayerinvolves____.

AserverBonlythetwoendsystems

CclientDrouter

42.A____layerprotocolprovidesforlogicalcommunicationbetweenapplications.

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,passesto____layer.

AApplication

BNetworking

CPhysical

DMAC

45.Inthefollowingfouroptions,whichoneiscorrect?

AThevariationsintheSampleRTTaresmoothedoutinthecomputationoftheEstimatedRTT

BThetimeoutshouldbelessthantheconnection’sRTT

CSupposethatthelastSampleRTTinaTCPconnectionisequalto1sec.ThenthecurrentvalueofTimeoutIntervalwillnecessarilybe≥1sec

DSupposethatthelastSampleRTTinaTCPconnectionisequalto1sec.ThenthecurrentvalueofTimeoutIntervalwillnecessarilybe≤1sec

46.TheportnumberusedbyHTTPis____.

A80

B25

C110

D53

47.TheportnumberusedbySMTPis____.

A80

B25

C110

D53

48.Theportnumberusedbypop3is____.

A80

B25

C110

D53

49.TheportnumberusedbyDNSis____.

A80

B25

C110

D53

50.TheportnumberusedbyFTPis____.

A20and21

B20

C21

D53

51.AUDPsocketidentifiedbya____tuple（s）.

A2

B4

C1

D3

52.ATCPsocketidentifiedbya____tuple（s）.

A2

B4

C1

D3

53.ATCPsocketdoesnotinclude____.

ASourceMACaddress

BSourceportnumber

CDestinationIPaddress

DDestinationportnumber

54.WhichoffollowingaboutUDPisnotcorrect.

AItisareliabledatatransferprotocol

BItisconnectionless

CnohandshakingbetweenUDPsender,receiver

Ditisabesteffortserviceprotocol

55.DNSuses____service.

ATCP

BUDP

CBothTCPandUDP

DNoneofabove

56.WhichoffollowingaboutUDPiscorrect?

AFinerapplication-levelcontroloverwhatdataissent,andwhen

BNoconnectionestablishment（whichcanadddelay）,sonodelayforestablishaconnection

CNoconnectionstate（so,UDPcantypicallysupportmanyactiveclients）

DLargepacketheaderoverhead（16-B）

57.Streamingmediausesa____servicenormally.

ATCP

BUDP

CBothTCPandUDP

DNoneofabove

58.TheUDPheaderhasonly____fields.

A2

B4

C1

D3

59.WhichofthefollowingdoesnotincludedinUDPheader.

ASourceportnumber

BDestinationportnumber

CChecksum

DSequencenumber

60.Whichofthefollowingisnotapipeliningprotocol.

ARdt1.0

BGo-Back-N

CSelectiverepeat

DTCP

61.InthefollowingfourdescriptionsaboutMSSandMTU,whichoneisnotcorrect?

ATheMSSisthemaximumamountofapplication-layerdatainthesegment

BTheMSSisthemaximumsizeoftheTCPsegmentincludingheaders

CTheMSSistypicallysetbyMTU

DTheMTUmeansthe