高级网络技术-upper_layers(思科教材)

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1、UpperLayers(上层)Objectives（目标）RolesoftheTransportLayer（传输层的角色）TheTCPProtocol–CommunicatingwithReliability（TCP协议-可靠传输）MostusedApplicationLayerProtocols（常用应用层协议）ARealCase（实例）RolesoftheTransportLayerTwoDifferentTransportServicesTCPandUDPTCPConnection-oriented(面向连接)Reliabledelivery(可靠传输)Flow

2、control(流控)ApplicationsthatuseTCP:WebBrowsers;E-mailFileTransfersUDPSimpleConnectionless(无连接)Lowoverhead(低开销)Besteffort(尽力而为)ApplicationsthatuseUDP:DomainNameSystem(DNS);VideoStreaming;VoiceoverIP(VoIP)PortAddressingUsedforIdentifyingtheConversationsPortAddressingTypesofportnumbersPortA

3、ddressingnetstatCommandTheTCPProtocol–CommunicatingwithReliabilityTCP–MakingConversationsReliableTCPsegment(分割)TCPServerProcessTCPConnectionEstablishment(确定)andTermination（终止）EstablishmentofTCPsessionsTCPConnectionEstablishmentandTerminationTerminationofTCPsessionsApplicationLayerProtoc

4、olsandServicesTCP/IPapplicationlayerprotocolsfitroughlyintotheframeworkofthetopthreelayersoftheOSImodel:Application,PresentationandSessionlayers.OSIandTCP/IPModelComparisonMostWidely-knownTCP/IPApplicationLayerProtocolsTheClient-SeverModelIntheclient/servermodel,thedevicerequestingthein

5、formationiscalledaclientandthedevicerespondingtotherequestiscalledaserver.Domainnameswerecreatedtoconvert（转换）thenumeric（数字的）addressintoasimple,recognizablename.DNSServicesandProtocolDNSServicesandProtocolnslookupcommandDNSServicesandProtocolTheDNSserverstoresdifferenttypesofresourcereco

6、rdsusedtoresolvenames.Theserecordscontainthename,address,andtypeofrecord.DNSServicesandProtocolAhierarchyofDNSserverscontainstheresourcerecordsthatmatchnameswithaddresses.WWWServiceandHTTPEntering‘http://www.cisco.com’intheaddressbarofawebbrowsergeneratestheHTTP‘GET’Message.WWWServicean

7、dHTTPInresponsetotherequest,theHTTPserverreturnscodeforawebpage.WWWServiceandHTTPThebrowserinterpretstheHTMLcodeanddisplaysawebpage.E-mailServicesandSMTP/POPProtocolsClientssende-mailstoaserverusingSMTPandreceivee-mailsusingPOP3.E-mailServicesandSMTP/POPProtocolsE-mailServer–MT