二章课后习题及答案.docx

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1、第二章1.(Q2)Foracommunicationsessionbetweenapairofprocesses,whichprocessistheclientandwhichistheserver?Answer:Theprocesswhichinitiatesthecommunicationistheclient。theprocessthatwaitstobecontactedistheserver..2.(Q3)Whatisthedifferencebetweennetworkarchitectureandapplicationarchite

2、cture?Answer:Networkarchitecturereferstotheorganizationofthecommunicationprocessintolayers(e.g.,thefive-layerInternetarchitecture).Applicationarchitecture,ontheotherhand,isdesignedbyanapplicationdeveloperanddictatesthebroadstructureoftheapplication(e.g.,client-serverorP2P)3.(

3、Q4)Whatinformationisusedbyaprocessrunningononehosttoidentifyaprocessrunningonanotherhost?Answer:TheIPaddressofthedestinationhostandtheportnumberofthedestinationsocket.4.(Q6)ReferringtoFigure2.4,weseethatnoneoftheapplicationlistedinFigure2.4requiresbothnodatalossandtiming.Cany

4、ouconceiveofanapplicationthatrequiresnodatalossandthatisalsohighlytime-sensitive?Answer:Therearenogoodexampleofanapplicationthatrequiresnodatalossandtiming.Ifyouknowofone,sendane-mailtotheauthors5.(Q9)WhydoHTTP,FTP,SMTP,andPOP3runontopofTCPratherthanonUDP?Answer:Theapplicatio

5、nsassociatedwiththoseprotocolsrequirethatallapplicationdatabereceivedinthecorrectorderandwithoutgaps.TCPprovidesthisservicewhereasUDPdoesnot.6.(Q11)Whatismeantbyahandshakingprotocol?Answer:Aprotocoluseshandshakingifthetwocommunicatingentitiesfirstexchangecontrolpacketsbefores

6、endingdatatoeachother.SMTPuseshandshakingattheapplicationlayerwhereasHTTPdoesnot.7.(Q13)TelnetintoaWebserverandsendamultilinerequestmessage.IncludeintherequestmessagetheIf-modified-since:headerlinetoforcearesponsemessagewiththe304NotModifiedstatuscode.6/6Answer:Issuedthefollo

7、wingcommand(inWindowscommandprompt)followedbytheHTTPGETmessagetothe“utopia.poly.edu”webserver:>telnetutopia.poly.edu80Sincetheindex.htmlpageinthiswebserverwasnotmodifiedsinceFri,18May200709:23:34GMT,thefollowingoutputwasdisplayedwhentheabovecommandswereissuedonSat,19May2007.N

8、otethatthefirst4linesaretheGETmessageandheaderlinesinputbytheuserand