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1、第一章1.(Q1)Whatisthedifferencebetweenahostandanendsystem?Listthetypesofendsystems.IsaWebserveranendsystem?Answer:Thereisnodifference.Throughoutthistext,thewords“host”and“endsystem”areusedinterchangeably.EndsystemsincludePCs,workstations,Webservers,mailservers,Internet-connectedPDAs,WebTVs,etc.2.
2、(Q2)Thewordprotocolisoftenusedtodescribediplomaticrelations.Giveanexampleofadiplomaticprotocol.Answer:SupposeAlice,anambassadorofcountryAwantstoinviteBob,anambassadorofcountryB,overfordinner.Alicedoesn’tsimplyjustcallBobonthephoneandsay,cometoourdinnertablenow”.Instead,shecallsBobandsuggestsad
3、ateandtime.Bobmayrespondbysayinghe’snotavailablethatparticulardate,butheisavailableanotherdate.AliceandBobcontinuetosend“messages”backandforthuntiltheyagreeonadateandtime.Bobthenshowsupattheembassyontheagreeddate,hopefullynotmorethan15minutesbeforeoraftertheagreedtime.Diplomaticprotocolsalsoal
4、lowforeitherAliceorBobtopolitelycanceltheengagementiftheyhavereasonableexcuses.3.(Q3)Whatisaclientprogram?Whatisaserverprogram?Doesaserverprogramrequestandreceiveservicesfromaclientprogram?Answer:Anetworkingprogramusuallyhastwoprograms,eachrunningonadifferenthost,communicatingwitheachother.The
5、programthatinitiatesthecommunicationistheclient.Typically,theclientprogramrequestsandreceivesservicesfromtheserverprogram.4.(Q4)Listsixaccesstechnologies.Classifyeachoneasresidentialaccess,companyaccess,ormobileaccess.Answer:1.Dial-upmodemovertelephoneline:residential;2.DSLovertelephoneline:re
6、sidentialorsmalloffice;3.CabletoHFC:residential;4.100MbpsswitchedEtherent:company;5.WirelessLAN:mobile;6.Cellularmobileaccess(forexample,3G/4G):mobile5.(Q5)Listtheavailableresidentialaccesstechnologiesinyourcity.Foreachtypeofaccess,providetheadvertiseddownstreamrate,upstreamrate,andmonthlypric
7、e.Answer:Currentpossibilitiesinclude:dial-up(upto56kbps);DSL(upto1Mbpsupstream,upto8Mbpsdownstream);cablemodem(upto30Mbpsdownstream,2Mbpsupstream.6.(Q7)WhataresomeofthephysicalmediathatEthernetcanrunover?Answer:Ethernetmostcommonlyrunso
