全套英文版《计算机网络》ppt电子课件教案

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1、Chapter2:ApplicationLayerChaptergoals:conceptual+implementationaspectsofnetworkapplicationprotocolsclientserverparadigmservicemodelslearnaboutprotocolsbyexaminingpopularapplication-levelprotocolsMorechaptergoalsspecificprotocols:httpftpsmtppopdnsprogrammin

2、gnetworkapplicationssocketprogramming12:ApplicationLayerApplicationsandapplication-layerprotocolsApplication:communicating,distributedprocessesrunninginnetworkhostsin“userspace”exchangemessagestoimplementappe.g.,email,filetransfer,theWebApplication-layerpr

3、otocolsone“piece”ofanappdefinemessagesexchangedbyappsandactionstakenuserservicesprovidedbylowerlayerprotocolsapplicationtransportnetworkdatalinkphysicalapplicationtransportnetworkdatalinkphysicalapplicationtransportnetworkdatalinkphysical22:ApplicationLaye

4、rNetworkapplications:somejargonAprocessisaprogramthatisrunningwithinahost.Withinthesamehost,twoprocessescommunicatewithinterprocesscommunicationdefinedbytheOS.Processesrunningindifferenthostscommunicatewithanapplication-layerprotocolAuseragentisaninterface

5、betweentheuserandthenetworkapplication.Web:browserE-mail:mailreaderstreamingaudio/video:mediaplayer32:ApplicationLayerClient-serverparadigmTypicalnetworkapphastwopieces:clientandserverapplicationtransportnetworkdatalinkphysicalapplicationtransportnetworkda

6、talinkphysicalClient:initiatescontactwithserver(“speaksfirst”)typicallyrequestsservicefromserver,forWeb,clientisimplementedinbrowser;fore-mail,inmailreaderServer:providesrequestedservicetocliente.g.,WebserversendsrequestedWebpage,mailserverdeliverse-mailre

7、questreply42:ApplicationLayerApplication-layerprotocols(cont).API:applicationprogramminginterfacedefinesinterfacebetweenapplicationandtransportlayersocket:InternetAPItwoprocessescommunicatebysendingdataintosocket,readingdataoutofsocketQ:howdoesaprocess“ide

8、ntify”theotherprocesswithwhichitwantstocommunicate?IPaddressofhostrunningotherprocess“portnumber”-allowsreceivinghosttodeterminetowhichlocalprocessthemessageshouldbedelivered…lotsmoreonthislater.52:Applicatio