tcp ip 协议族15章new

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1、CHAPTER15TransmissionControlProtocol(TCP)Exercises1.SeeTable15.E1.Table15.E1SolutiontoExercise1FieldsUDPTCPPurposeSourcePortNumber√√TodefinethesourceportnumberDestinationPortNumber√√TodefinethedestinationportnumberChecksum√√ForerrorcontrolTotalLength√Itis

2、notactuallyneededeveninUDPSequenceNumber√ForflowcontrolAcknowledgmentNumber√ForflowcontrolHeaderLength√TodefinevariableheaderlengthinTCPControlBits√TodefinedifferenttypeofsegmentsUrgentPointer√TodefinetheendofurgentdataOptionsAndPadding√TomakeTCPtousediff

3、erentoptionsNotethattheonlyfieldthatexistsinUDP,butismissinginTCP,isthetotallengthfield.ThedesignerofTCPdidnotfeelthatthisfieldisneededbecausethesizeoftheTCPsegmentcanbedeterminedfromthesizeoftheIPdatagramthatcarriesit.3.Theportisnotlistedinthetransmissio

4、ncontrolblock,whichmeansnoprocessisrunningassociatedtothisport.5.a.ThemaximumsizeoftheTCPheaderis60bytes(20bytesofheaderandamaximum40bytesofoptions).b.TheminimumsizeoftheTCPheaderis20bytes.1SECTION27.SeeFigure15.E7.Figure15.E7SolutiontoExercise75200120or2

5、114532785751501100020000040bytesofdata9.a.Thesourceportnumberis0532inhexand1330indecimal.b.Thedestinationportnumberis0017inhexand23indecimal.c.Thesequencenumberis00000001inhexand1indecimal.d.Theacknowledgmentnumberis00000000inhexand0indecimal.e.TheHLEN=5.

6、Theheaderis5×4=20byteslong.f.Thecontrolfieldis002inhex.ThisindicatesaSYNsegmentusedforconnec-tionestablishment.g.Thewindowsizefieldis07FFinhexand2047indecimal.Thewindowsizeis2047bytes.11.Everysecondthecounterisincrementedby64,000×2=128,000.Thesequencenumb

7、erfieldis32bitslongandcanholdonly232−1.Soittakes(232−1)/(128,000)or33,554secondstowraparound.13.Thewindowsizeisthesmaller(3000,5000)=3000.Since2000bytesisalreadysent,only3000−2000=1000morebytescanbesent.15.Thedatasectionisonly16bytes.TheTCPheaderis20bytes

8、.IPheaderis20bytes.Theheaderandtraileris19bytes(withoutpreamble).Wecancalculatetheefficiencyateachlayer:a.AtTCPlevel:(16)/(16+20)=0.444→44.4%b.AtIPlevel:(16)/(16+20+20)=28.57→28.57%c.Atdatalinklevel:(16)/(16+20+20+1