计算机网络英文题库(附答案)chapter3.doc
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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____.
A0100010001000011
B1011101110111100
C1111111111111111
D1000000000000000
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.
AUDP BTCP CDNS DHTTP
38.ThehostthatinitiatesthesessionintheInternetislabeledas____.
Aserver Buseragent Cclient Drouter
39.WithTCPthereisno_____betweensendingandreceivingtransport-layerentities.
Aflowcontrol Bhandshaking
C.congestioncontrol DVCsetup
40.TheInternet’s____servicehelpspreventtheInternetfromenteringastateofgridlock.
Adatagram Bcongestioncontrol
Cslidingwindow Dtimeoutevent
41.Connectionsetupatthetransportlayerinvolves____.
Aserver Bonlythetwoendsystems
Cclient Drouter
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
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