體驗(yàn)性學(xué)習(xí)在小學(xué)低年級語文教學(xué)中 ..

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1、15-441ComputerNetworkingLecture18–MoreTCP&CongestionControlGoodIdeasSoFar…FlowcontrolStop&waitParallelstop&waitSlidingwindow(e.g.,advertisedwindows)LossrecoveryTimeoutsAcknowledgement-drivenrecovery(selectiverepeatorcumulativeacknowledgement)CongestioncontrolAIMD?fa

2、irnessandefficiencyHowdoesTCPactuallyimplementthese?10-31-20062Lecture18:TCPDetailsOutlineTHESPOOKYPARTSofTCPIfitdoesn’tscareyounow…itwillontheFinal!TCPconnectionsetup/datatransferTheCandy-exchangeProtocol(TCP)TCPreliabilityHowtorecoveryourDEADpacketsTCPcongestionav

3、oidanceAvoidingthedeath-trapsofoverloadedrouters10-31-20063Lecture18:TCPDetailsSequenceNumberSpaceEachbyteinbytestreamisnumbered.32bitvalueWrapsaroundInitialvaluesselectedatstartuptimeTCPbreaksupthebytestreamintopackets.PacketsizeislimitedtotheMaximumSegmentSizeEach

4、packethasasequencenumber.Indicateswhereitfitsinthebytestreampacket8packet9packet101345014950160501755010-31-20064Lecture18:TCPDetailsEstablishingConnection:Three-WayhandshakeEachsidenotifiesotherofstartingsequencenumberitwilluseforsendingWhynotsimplychose0?Mustavoi

5、doverlapwithearlierincarnationSecurityissuesEachsideacknowledgesother’ssequencenumberSYN-ACK:Acknowledgesequencenumber+1CancombinesecondSYNwithfirstACKSYN:SeqCACK:SeqC+1SYN:SeqSACK:SeqS+1ClientServer10-31-20065Lecture18:TCPDetailsTCPConnectionSetupExampleClientSYNSe

6、qC:Seq.#4019802004,window65535,max.seg.1260ServerSYN-ACK+SYNReceive:#4019802005(=SeqC+1)SeqS:Seq.#3428951569,window5840,max.seg.1460ClientSYN-ACKReceive:#3428951570(=SeqS+1)09:23:33.042318IP128.2.222.198.3123>192.216.219.96.80:S4019802004:4019802004(0)win65535

7、60,nop,nop,sackOK>(DF)09:23:33.118329IP192.216.219.96.80>128.2.222.198.3123:S3428951569:3428951569(0)ack4019802005win5840(DF)09:23:33.118405IP128.2.222.198.3123>192.216.219.96.80:.ack3428951570win65535(DF)10-31-20066Lecture18:TCPDetailsTCPSta

8、teDiagram:ConnectionSetupCLOSEDSYNSENTSYNRCVDESTABLISTENactiveOPENcreateTCBSndSYNcreateTCBpassiveOPENdeleteTCBCLOSEdeleteTCBCLOSEsndSYNSEN