2.+第二章课后习题及答案

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

2、pplicationarchitecture?Answer:Networkarchitecturereferstotheorganizationofthecommunicationprocessintolayers(e.g.,thefive-layerInternetarchitecture).Applicationarchitecture,ontheotherhand,isdesignedbyanapplicationdeveloperanddictatesthebroadstructureoftheappli

3、cation(e.g.,client-serverorP2P)3.(Q4)Whatinformationisusedbyaprocessrunningononehosttoidentifyaprocessrunningonanotherhost?Answer:TheIPaddressofthedestinationhostandtheportnumberofthedestinationsocket.4.(Q6)ReferringtoFigure2.4,weseethatnoneoftheapplicationli

4、stedinFigure2.4requiresbothnodatalossandtiming.Canyouconceiveofanapplicationthatrequiresnodatalossandthatisalsohighlytime-sensitive?Answer:Therearenogoodexampleofanapplicationthatrequiresnodatalossandtiming.Ifyouknowofone,sendane-mailtotheauthors5.(Q9)WhydoHT

5、TP,FTP,SMTP,andPOP3runontopofTCPratherthanonUDP?Answer:Theapplicationsassociatedwiththoseprotocolsrequirethatallapplicationdatabereceivedinthecorrectorderandwithoutgaps.TCPprovidesthisservicewhereasUDPdoesnot.6.(Q11)Whatismeantbyahandshakingprotocol?Answer:Ap

6、rotocoluseshandshakingifthetwocommunicatingentitiesfirstexchangecontrolpacketsbeforesendingdatatoeachother.SMTPuseshandshakingattheapplicationlayerwhereasHTTPdoesnot.7.(Q13)TelnetintoaWebserverandsendamultilinerequestmessage.IncludeintherequestmessagetheIf-mo

7、dified-since:headerlinetoforcearesponsemessagewiththe304NotModifiedstatuscode.Answer:Issuedthefollowingcommand(inWindowscommandprompt)followedbytheHTTPGETmessagetothe“utopia.poly.edu”webserver:>telnetutopia.poly.edu80Sincetheindex.htmlpageinthiswebserverwasno

8、tmodifiedsinceFri,18May200709:23:34GMT,thefollowingoutputwasdisplayedwhentheabovecommandswereissuedonSat,19May2007.Notethatthefirst4linesaretheGETmessageandheaderlinesinputbytheuserandthe