CHAPTER3:TRANSPORTLAYER

Atransport-layerprotocolprovidesforlogicalcommunicationbetweenC_.

Routers

Hosts

Applicationprocesses

Endsystems

Transport-layerprotocolsrunin—D—.

Servers

Clients

Routers

Endsystems

Intransportlayer,thesendsidebreaksapplicationmessagesintoB_,passesto

networklayer.

Frames

Segments

Data-grams

bitstreams

Thereceivesideoftransportlayerreassemblessegmentsintomessages,passesto

—A—layer.

Application

Networking

Physical

MAC

Servicesprovidedbytransportlayerinclude—C—.

HTTPandFTP

TCPandIP

TCPandUDP

SMTP

WhichofthefollowingservicesisnotprovidedbyTCP?D

In-orderdatatransfers

Reliabledatatransfersandflowcontrols

Congestioncontrols

Delayguaranteesandbandwidthguarantees

Thesetwominimaltransport-layerservices——A_and——aretheonlytwoservicesthatUDPprovides

process-to-processdatadelivery,errorchecking

congestioncontrol,reliabledatatransfer

flowcontrol,congestioncontrol

In-orderdatatransfer,errorchecking

UDPofferswhichofthefollowingbenefitsrelativetoTCP?C

A.UDPguaranteesthatIndividualpacketsofatransmissionwillarrive“inorder”B.UDPsupportsaself-regulating“throttle”featurethatpreventsnetworksaturation

C.UDPconsumesfewercomputerresourcesbynotmaintainingconnectionstateD.Noneoftheabove

WhichofthefollowingapplicationsnormallyusesUDPservices?B

SMTP

Streamingmultimedia

FTP

HTTP

Thejobofgatheringdatachunks,encapsulatingeachdatachunkwithheaderinformationtocreatesegmentsandpassingthesegmentstothenetworkiscalled__A__.

multiplexing

de-multiplexing

forwarding

routing

Thisjobofdeliveringthedatainatransport-layersegmenttothecorrectsocketiscalled_B.

multiplexing

de-multiplexing

forwarding

routing

Portnumber,sscopeisB_to.

A.0,1023

B.0,65535

C.0,127

D.0,255

Theportnumbersrangingfrom_C_toarecalledwell-knownportnumber

andarerestricted.

A.0,127

B.0,65535

C.0,1023

D.0,255

TheUDPheaderhasonlyfourfields,theyare—A—.

Sourceportnumber,destinationportnumber,lengthandchecksum

Sourceportnumber,destinationportnumber,sourceIPanddestinationIP

sourceIP,destinationIP,sourceMACaddressanddestinationMACaddressD.sourceIP,destinationIP,sequencenumberandACKsequencenumber

ThefieldofLengthinUDPsegmentspecifiesthelengthofB_.

theUDPsegment,notincludingtheheader

theUDPsegment,includingtheheader

theUDPsegment,sheader

theLengthfield

WhichofthefollowingaboutTCPconnectionisnotcorrect?A

Itisabroadcastconnection

Itisapoint-to-pointconnection

Itisapipelinedconnection

Itisafullduplexconnection

InthefollowingfourdescriptionsaboutMSSandMTU,whichoneisnotcorrect?CA.TheMSSistypicallysetbyMTU

TheMSSisthemaximumsizeoftheTCPsegmentincludingheaders

TheMSSisthemaximumamountofapplication-layerdatainthesegment

TheMTUmeansthelargestlink-layerframe

—A_isthebytestreamnumberoffirstbyteinthesegment.

Sequencenumber

ACKnumber

Checksum

portnumber

—B_isthebytesequencenumbersofnextbyteexpectedfromotherside.

Sequencenumber

ACKnumber

Checksum

portnumber

Inthefollowingfouroptions,whichoneiscorrect?D

SupposethatthelastSampleRTTinaTCPconnectionisequalto1sec.ThenthecurrentvalueofTimeoutIntervalwillnecessarilybeW1sec

Thetimeoutshouldbelessthantheconnection,sRTT

SupposethatthelastSampleRTTinaTCPconnectionisequalto1sec.ThenthecurrentvalueofTimeoutIntervalwillnecessarilybeN1sec

ThevariationsintheSampleRTTaresmoothedoutinthecomputationoftheEstimatedRTT

Therearetwo16-bitintegers:1110011001100110,1101010101010101.Theirchecksumis—A—.

A.0100010001000011

B.1011101110111100

C.1111111111111111

D.1000000000000000

SupposehostAsendshostBoneTCPsegmentwithsequencenumber418,acknowledgementnumber571,and4bytesofdata.ThenthesequencenumberintheacknowledgementtothissegmentisC

A.422

B.418

C.571

D.575

BecauseTCPonlyacknowledgesbytesuptothefirstmissingbyteinthestream,TCPissaidtoprovide—D—.

positiveACKs

Selectiveacknowledgements

3duplicateACKs

Cumulativeacknowledgements

IfwedefineNtobethewindowsize,basetobethesequencenumberoftheoldestunacknowledgedpacket,andnext-seq-numtobethesmallestunusedsequencenumber,thentheinterval[nextseqnum,base+N-1]correspondstopacketthat__A__.

canbesentimmediately

havealreadybeentransmittedandacknowledged

cannotbeused

havebeensentbutnotyetacknowledged

Whichofthefollowingisnotapipeliningprotocol.A

Rdt1.0

Go-Back-N

Selectiverepeat

TCP

Whatisthemaindifferencebetweenstop-and-waitandpipelinedreliabledatatransferprotocol?B

ThepipelinedprotocolusestheNAKpackets,whereasinthestop-and-waitprotocolsendersalwayswaitforACKpackets.

Withthepipelinedprotocol,thesendercansendseveralpacketsinrow,whereasinthestop-and-waitprotocolthesendercannotsendthepacketsinrow.

Withthepipelinedprotocol,thereceivermustsendoneACKforseveralpackets(cumulativeACK),whereasinthestop-and-waitprotocolthereceivercannotsendthecumulativeACK.

Thepipelinedprotocolusestimeouts,whereasthestop-and-waitprotocoldoesnotusethetimeout.

Fastretransmitmeansinthecasethat—D_duplicateACK-sarereceived,theTCPsenderresendsegmentbeforetimerexpires.

6

5

4

3

—B_isaspeeding-matchingservice-matchingtheratewhichthesenderissendingagainsttherateatwhichthereceivingapplicationisreading.

congestioncontrol

flowcontrol

sliding-windowcontrol

variablecontrol

TCPprovidesflowcontrolbyhavingthesendermaintainavariablecalledthe__D__.

buffer

Congestionwindow

Slidingwindow

Receivewindow

ProvidedRcvBuffer=20,LastByteRcvd=20,LastByteRead=15,thenRcvWindow二—B—.

14

15

16

10

InthefollowingfourdescriptionsaboutTCPconnectionmanagement,whichoneisnotcorrect?D

EitherofthetwoprocessesparticipatinginaTCPconnectioncanendtheconnection

IftheFINbitissetto1,itmeansthatitwantstoclosetheconnection

Inthefirsttwostepofthethree-wayhandshake,theclientandserverrandomlychooseaninitialsequencenumber

Inthethreesegmentsofthethree-wayhandshake,theSYNbitmustbesetto1

HowdoesTCPsenderperceivecongestion?D

Throughatimeoutevent

Throughareceiving