计算机网络实验三参考答案

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1、1.WhatistheIPaddressandTCPportnumberusedbytheclientcomputer(source)thatistransferringthefiletogaia.cs.umass.edu?Toanswerthisquestion,it’sprobablyeasiesttoselectanHTTPmessageandexplorethedetailsoftheTCPpacketusedtocarrythisHTTPmessage,usingthe“detailsoftheselectedpacketheaderwindow”(refertoFig

2、ure2inthe“GettingStartedwithWireshark”Labifyou’reuncertainabouttheWiresharkwindows).Ans:IPaddress:192.168.1.102TCPport:11612.WhatistheIPaddressofgaia.cs.umass.edu?OnwhatportnumberisitsendingandreceivingTCPsegmentsforthisconnection?Ans:IPaddress:128.119.245.12TCPport:80Ifyouhavebeenabletocreat

3、eyourowntrace,answerthefollowingquestion:3.WhatistheIPaddressandTCPportnumberusedbyyourclientcomputer(source)totransferthefiletogaia.cs.umass.edu?ANS:IPaddress:10.211.55.7TCPport:492654.WhatisthesequencenumberoftheTCPSYNsegmentthatisusedtoinitiatetheTCPconnectionbetweentheclientcomputerandgai

4、a.cs.umass.edu?WhatisitinthesegmentthatidentifiesthesegmentasaSYNsegment?ANS:sequencenumber:0SynSet=1identifiesthesegmentasaSYNsegment5.WhatisthesequencenumberoftheSYNACKsegmentsentbygaia.cs.umass.edutotheclientcomputerinreplytotheSYN?WhatisthevalueoftheACKnowledgementfieldintheSYNACKsegment?

5、Howdidgaia.cs.umass.edudeterminethatvalue?WhatisitinthesegmentthatidentifiesthesegmentasaSYNACKsegment?ANS:Thesequencenumber:0ACKnowledgementnumber:1whichissequencenumberplus1BoththesequenceflagandtheACKnowledgementflagbeensetas1,identifiesthesegmentasSYNACKsegment.6.Whatisthesequencenumberof

6、theTCPsegmentcontainingtheHTTPPOSTcommand?NotethatinordertofindthePOSTcommand,you’llneedtodigintothepacketcontentfieldatthebottomoftheWiresharkwindow,lookingforasegmentwitha“POST”withinitsDATAfield.Ans:Thesequencenumber:17.ConsidertheTCPsegmentcontainingtheHTTPPOSTasthefirstsegmentintheTCPcon

7、nection.WhatarethesequencenumbersofthefirstsixsegmentsintheTCPconnection(includingthesegmentcontainingtheHTTPPOST)?Atwhattimewaseachsegmentsent?WhenwastheACKforeachsegmentreceived?GiventhedifferencebetweenwheneachTCPsegmentwassent,andwhenitsa