计算机网络实验：Ethernet and ARP

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1、实用标准Lab7EthernetandARP1.CapturingandanalyzingEthernetframesSTEPS•First,makesureyourbrowser’scacheisempty.(TodothisunderNetscape7.0,selectEdit->Preferences->Advanced->Cacheandclearthememoryanddiskcache.ForInternetExplorer,selectTools->InternetOptions->DeleteFiles.ForFi

2、refoxselectTools->ClearPrivateData.•StartuptheWiresharkpacketsniffer•EnterthefollowingURLintoyourbrowserhttp://gaia.cs.umass.edu/wireshark-labs/HTTP-ethereal-lab-file3.htmlYourbrowsershoulddisplaytheratherlengthyUSBillofRights.•StopWiresharkpacketcapture.First,findthe

3、packetnumbers(theleftmostcolumnintheupperWiresharkwindow)oftheHTTPGETmessagethatwassentfromyourcomputertogaia.cs.umass.edu,aswellasthebeginningoftheHTTPresponsemessagesenttoyourcomputerbygaia.cs.umass.edu.Youshouldseeascreenthatlookssomethinglikethis(wherepacket4inthe

4、screenshotbelowcontainstheHTTPGETmessage)•SincethislabisaboutEthernetandARP,we’renotinterestedinIPorhigherlayerprotocols.Solet’schangeWireshark’s“listingofcapturedpackets”windowsothatitshowsinformationonlyaboutprotocolsbelowIP.TohaveWiresharkdothis,selectAnalyze->Enab

5、ledProtocols.ThenunchecktheIPboxandselectOK.QUESTIONS1.Whatisthe48-bitEthernetaddressofyourcomputer?文案大全实用标准The48-bitEthernetaddressofyourcomputeris3c:97:0e:ff:69:021.Whatisthe48-bitdestinationaddressintheEthernetframe?IsthistheEthernetaddressofgaia.cs.umass.edu?(Hint

6、:theanswerisno).WhatdevicehasthisasitsEthernetaddress?[Note:thisisanimportantquestion,andonethatstudentssometimesgetwrong.Re-readpages468-469inthetextandmakesureyouunderstandtheanswerhere.]The48-bitdestinationaddressintheEthernetframeis38:22:d6:e6:0e:0d.Thisisn’ttheEt

7、hernetaddressofgaia.cs.umass.edu.ItistheEthernetaddressofmydefaultgateway.Thatistosay,it’stheaddressofmyrouter,whichisthelinkusedtogetoffthesubnet.文案大全实用标准1.Givethehexadecimalvalueforthetwo-byteFrametypefield.Whatdothebit(s)whosevalueis1meanwithintheflagfield?Thehexad

8、ecimalvalueforthetwo-byteFrametypefieldis0x0800.Thebit(s)whosevalueis1withintheflagfieldmeanthefragmenthasnotbeenfragmented.