计算机概论Cha

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1、Chapter4:NetworkingandtheInternet4.1NetworkFundamentals4.2TheInternet4.3TheWorldWideWeb4.4InternetProtocols4.5Security1NetworkClassificationsScopeLocalAreaNetwork(LAN,局域网)MetropolitanAreaNetwork(MAN,城域网)WideAreaNetwork(WAN,广域网)OwnershipClosedvs.Open(封闭式网络vs.开放式网络)Topology(thepatternin

2、whichthemachinesareconnected)Bus(总线型)EthernetStar(星型)WirelessnetworkswithcentralAccessPoint2Figure4.1Networktopologies3Figure4.1Networktopologies(continued)4ProtocolsCSMA/CD（CarrierSense,MultipleAccesswithCollisionDetection,带冲突检测的载波侦听多路访问）UsedinEthernetSilentbusprovidesrighttointroduc

3、enewmessageCSMA/CA（CarrierSense,MultipleAccesswithCollisionAvoidance,带冲突避免的载波侦听多路访问）UsedinWiFiHiddenterminalproblem5Figure4.2Communicationoverabusnetwork6Figure4.3Thehiddenterminalproblem7ConnectingNetworksRepeater（中继器）:ExtendsanetworkBridge（网桥）:ConnectstwocompatiblenetworksSwitch（交换机

4、）:ConnectseveralcompatiblenetworksRouter（路由器）:Connectstwoincompatiblenetworksresultinginanetworkofnetworkscalledaninternet8Figure4.4Buildingalargebusnetworkfromsmallerones9Figure4.5RoutersconnectingtwoWiFinetworksandanEthernetnetworktoformaninternet10Inter-processCommunicationClient-s

5、erver（客户机/服务器模型）Oneserver,manyclientsServermustexecutecontinuouslyClientinitiatescommunicationPeer-to-peer(P2P，对等模型)TwoprocessescommunicatingasequalsPeerprocessescanbeshort-lived11Figure4.6Theclient/servermodelcomparedtothepeer-to-peermodel12DistributedSystems（分布式系统）Systemswithpartsth

6、atrunondifferentcomputersInfrastructurecanbeprovidedbystandardizedtoolkitsExample:EnterpriseJavaBeans（企业级JavaBeans）fromSunMicrosystemsExample:.NETframework（.NET框架）fromMicrosoft13TheInternetTheInternet:AninternetthatspanstheworldOriginalgoalwastodevelopameansofconnectingnetworksthatwou

7、ldnotbedisruptedbylocaldisasters.Todayithasshiftedfromanacademicresearchprojecttoacommercialundertaking.14InternetArchitectureInternetServiceProvider(ISP,应特网服务提供商）Tier-1Tier-2AccessISP(因特网接入服务提供商):ProvidesconnectivitytotheInternetTraditionaltelephone(dialupconnection)CableconnectionsD

8、SL（Di