计算机网络实验报告-实验五 探索TCP协议.doc -- 6 元

－1－陕西师范大学计算机网络实验报告实验五探索TCP协议一、实验目的1.熟悉并掌握wireshark的操作。2.通过实验分析并掌握TCP是如何进行数据传输的，及其如何实现拥塞控制、流量控制等二、实验器材1.PC机电脑一台。2．下载wireshark软件并安装三、实验内容通过实验分析并掌握TCP是如何进行数据传输的，及其如何实现拥塞控制、流量控制等四、问题回答1.CapturingabulkTCPtransferfromyourcomputertoaremoteServerGothehttp//gaia.cs.umass.edu/wiresharklabs/alice.txtandretrieveanASCIIcopyofAliceinWonderland.Storethisfile.somewhereonmycomputer.Nextgotohttp//gaia.cs.umass.edu/wiresharklabs/TCPwiresharkfile1.html.ThenIcanseeascreenthatlookslike－2－,startupWiresharkandbeginpacketcapture.Returningtobrowser,presstheUploadalice.txtfilebuttontouploadthefiletothegaia.cs.umass.eduserver.StopWiresharkpacketcapture.TheWiresharkwindowlikethisThenopeningtheWiresharkcapturedpacketfiletcpetherealtrace1inhttp//gaia.cs.umass.edu/wiresharklabs/wiresharktraces.zip－3－2.Afirstlookatthecapturedtrace1.WhatistheIPaddressandTCPportnumberusedbytheclientcomputersourcethatistransferringthefiletogaia.cs.umass.eduToanswerthisquestion,itsprobablyeasiesttoselectanHTTPmessageandexplorethedetailsoftheTCPpacketusedtocarrythisHTTPmessage,usingthedetailsoftheselectedpacketheaderwindowrefertoFigure2intheGettingStartedwithWiresharkLabifyoureuncertainabouttheWiresharkwindows.答clientcomputersourceIPaddress192.168.1.102ipaddressTcpportnumber－4－TCPportnumber11612.WhatistheIPaddressofgaia.cs.umass.eduOnwhatportnumberisitsendingandreceivingTCPsegmentsforthisconnection答theIPaddressofgaia.cs.umass.eduIPaddress128.119.245.12portnumber803.Ifyouhavebeenabletocreateyourowntrace,answerthefollowingquestionWhatistheIPaddressandTCPportnumberusedbyyourclientcomputersourcetotransferthefiletogaia.cs.umass.eduipaddressportnumber－5－答MyclientcomputerIPaddress10.2.136.30ipaddressTcpportnumberThenWiresharkdothis,selectAnalyzeEnabledProtocols.ThenunchecktheHTTPboxandselectOK.nowseeanWiresharkwindowthatlookslike－6－3.TCPBasicsAnswerthefollowingquestions4.WhatisthesequencenumberoftheTCPSYNsegmentthatisusedtoinitiatetheTCPconnectionbetweentheclientcomputerandgaia.cs.umass.eduWhatisitinthesegmentthatidentifiesthesegmentasaSYNsegment答sequencenumber0syn被设置为1说明是syn段。SequencenumberSynis1－7－5.WhatisthesequencenumberoftheSYNACKsegmentsentbygaia.cs.umass.edutotheclientcomputerinreplytotheSYNWhatisthevalueoftheACKnowledgementfieldintheSYNACKsegmentHowdidgaia.cs.umass.edudeterminethatvalueWhatisitinthesegmentthatidentifiesthesegmentasaSYNACKsegment答ThesequencenumberoftheSYNACKsegmentsentbygaia.cs.umass.eduis0SYNACKsegment中ACKnowledgement的值为1ACKnowledgementnumber的值为SYN消息中sequencenumber加上1所得SYN和Acknowledgementf都置为1说明这是一个SYNACKsegment.6.WhatisthesequencenumberoftheTCPsegmentcontainingtheHTTPPOSTcommandNotethatinordertofindthePOSTcommand,youllneedtodigintothepacketcontentfieldatthebottomoftheWiresharkwindow,lookingforasegmentwithaPOSTwithinitsDATAfield.SequencenumberThevalueoftheACKnowledgementfield