外文翻译--拥塞控制中的算法

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1、译文2TheAlgorithmofCongestionControl1．TahoeTCPModernTCPimplementationscontainanumberofalgorithmsaimedatcontrollingnetworkcongestionwhilemaintaininggooduserthroughput.EarlyTCPimplementationsfollowedago-back-n.modelusingcumulativepositiveacknowledgmentandrequiringaretransmittimerexpirationtore-senddata

2、lostduringtransport.TheseTCPsdidlittletominimizenetworkcongestion.TheTahoeTCPimplementationaddedanumberofnewalgorithmsandrefinementstoearlierimplementations.ThenewalgorithmsincludeSlow-Start,CongestionAvoidance,andFastRetransmit.Therefinementsincludeamodificationtotheround-triptimeestimatorusedtose

3、tretransmissiontimeoutvalues.Allmodificationshavebeendescribedelsewhere.TheFastRetransmitalgorithmisofspecialinterestinthispaperbecauseitismodifiedsubsequentversionsofTCP.WithFastRetransmit,afterreceivingasmallnumberofduplicateacknowledgmentsforthesameTCPsegment(dupACKs),thedatasenderinfersthatapac

4、kethasbeenlostandretransmitsthepacketwithoutwaitingforaretransmissiontimertoexpire,leadingtohigherchannelutilizationandconnectionthroughput.2．RenoTCPTheRenoTCPimplementationretainedtheenhancementsincorporatedintoTahoe,butmodifiedtheFastRetransmitoperationtoincludeFastRecovery.Thenewalgorithmprevent

5、sthecommunicationpath(“pipe”)fromgoingemptyafterFastRetransmit,therebyavoidingtheneedtoSlow-Starttorefillitafterasinglepacketloss.FastRecoveryoperatesbyassumingeachdupACKreceivedrepresentsasinglepackethavingleftthepipe.Thus,duringFastRecoverytheTCPsenderisabletomakeintelligentestimatesoftheamountof

6、outstandingdata.InReno,thesender'susablewindowbecomesothergatewaysthatfailtomonitortheaveragequeuesize)untilthenumberofdupACKsreachestcprexmtthresh,andthereaftertracksthenumberofduplicateACKs.Thus,duringFastRecoverythesender“inflate”itswindowbythenumberofdupACKsithasreceived,accordingtotheobservati

7、onthateachdupACKindicatessomepackethasbeenremovedfromthenetworkandisnowcachedatthereceiver.AfterenteringFastRecoveryandretransmittingasinglepacket,thesendereffectivelywaitsuntilhalfawindowofdupACKshavebeenr