外文翻译--拥塞控制中的算法

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1、译文2TheAlgorithmofCongestionControl1．TahoeTCPModernTCPimplementationscontainanumberofalgorithmsaimedatcontrollingnetworkcongestionwhilemaintaininggooduserthroughput.EarlyTCPimplementationsfollowedago-back-n.modelusingcumulativepositiveacknowledgmentandrequiringar

2、etransmittimerexpirationtore-senddatalostduringtransport.TheseTCPsdidlittletominimizenetworkcongestion.TheTahoeTCPimplementationaddedanumberofnewalgorithmsandrefinementstoearlierimplementations.ThenewalgorithmsincludeSlow-Start,CongestionAvoidance,andFastRetrans

3、mit.Therefinementsincludeamodificationtotheround-triptimeestimatorusedtosetretransmissiontimeoutvalues.Allmodificationshavebeendescribedelsewhere.TheFastRetransmitalgorithmisofspecialinterestinthispaperbecauseitismodifiedsubsequentversionsofTCP.WithFastRetransmi

4、t,afterreceivingasmallnumberofduplicateacknowledgmentsforthesameTCPsegment(dupACKs),thedatasenderinfersthatapackethasbeenlostandretransmitsthepacketwithoutwaitingforaretransmissiontimertoexpire,leadingtohigherchannelutilizationandconnectionthroughput.2．RenoTCPTh

5、eRenoTCPimplementationretainedtheenhancementsincorporatedintoTahoe,butmodifiedtheFastRetransmitoperationtoincludeFastRecovery.Thenewalgorithmpreventsthecommunicationpath(“pipe”)fromgoingemptyafterFastRetransmit,therebyavoidingtheneedtoSlow-Starttorefillitafteras

6、inglepacketloss.FastRecoveryoperatesbyassumingeachdupACKreceivedrepresentsasinglepackethavingleftthepipe.Thus,duringFastRecoverytheTCPsenderisabletomakeintelligentestimatesoftheamountofoutstandingdata.InReno,thesender'susablewindowbecomesothergatewaysthatfailtom

7、onitortheaveragequeuesize)untilthenumberofdupACKsreachestcprexmtthresh,andthereaftertracksthenumberofduplicateACKs.Thus,duringFastRecoverythesender“inflate”itswindowbythenumberofdupACKsithasreceived,accordingtotheobservationthateachdupACKindicatessomepackethasbe

8、enremovedfromthenetworkandisnowcachedatthereceiver.AfterenteringFastRecoveryandretransmittingasinglepacket,thesendereffectivelywaitsuntilhalfawindowofdupACKshavebeenr