教学材料《计算机》-2-5 Protocols

2-5ProtocolsAttheclassificationofnetworksfordatatransmissiontobesuccessful,senderandreceivermustfollowasetofcommunicationrulesfortheexchangeofinformation.Theserulesforexchangingdatabetweencomputersareknownastheprotocol.Therulescanbeunderstoodasakindofcommonlanguagecanunderstandeachother.分类组建网络时，为了成功传输数据，发送方和接收方必须遵循用以交换信息的一套规则。这些计算机间交换数据的规则被称之为协议。这套规则可以理解为一种彼此都能听得懂的公用语言。Keywords:receiver[rɪ'siːvə]n.接收器exchange

[ɪks'tʃendʒ]n.交换protocol

['prəʊtəkɒl]n.协议2-5ProtocolsTherearetowkindsofprotocolaboutthenetwork:"internalagreement"and"externalagreement".Internalagreement：in1978,theinternationalorganizationforstandardization(ISO)setastandardfornetworkcommunicationModel,calledtheOSI/RM(OpenSystemInterconnect/ReferenceModel).网络中的协议有两类：“内部协议”和“外部协议”。内部协议：1978年，国际标准化组织（ISO）为网络通信制定了一个标准模式，称为OSI/RM（OpenSystemInterconnect/ReferenceModel，开放系统互联/参考模型）体系结构。Expandedvocabulary:referenceModel参考模型2-5ProtocolsThestructureisdividedintosevenlayers,whichfromlowtohighrespectivelyisthephysicallayer,datalinklayer,networklayer,transportlayer,sessionlayer,presentationlayer

andapplicationlayer.Anynetworkdeviceoftheupperandlowerlayer,hasitsspecificagreement.同时在两个设备（如工作站与服务器）的同层之间也有协议约定。该结构共分七层，从低到高分别是物理层、数据链路层、网络层、传输层、会话层、表示层和应用层。任何一个网络设备的上下层之间都有其特定的协议形式。Expandedvocabulary:physicallayer物理层datalinklaye数据链路层networklayer网络层transportlayer传输层sessionlayer会话层presentationlayer表示层applicationlayer应用层2-5ProtocolsAtthesametime,thesamelayerbetweenthetwodevices,suchasworkstationsandserversalsohasitsagreement.Here,theseagreementsaredefinedas"internalagreement".Externalprotocol:externalnetworkformationmustbeselectedbyagreement.Becauseitisdirectlyresponsibleforthecomputertocommunicatewitheachother,externalprotocolissooftenreferredtoasanetworkcommunicationprotocol.同时在两个设备（如工作站与服务器）的同层之间也有协议约定。在这里，这些协议全部定义为“内部协议”。外部协议即组网时所必须选择的协议。它由于直接负责计算机之间的相互通信，所以通常称为网络通信协议。Expandedvocabulary:referredtoas被称为2-5ProtocolsAtfirstthedevelopmentagreementofeachcompanyistofittheirownnetworkcommunication,butwiththepopularityofnetworkapplications,requirementsofinterconnectionbetweendifferentnetworkshavebecomemoreandmoreurgent,sothecommunicationprotocolhasbecomethekeytechnologiestosolveproblemsbetweenthenetworkinterconnection.最初每家公司开发的协议，都是为了满足自己的网络通信，但随着网络应用的普及，不同网络之间进行互联的要求越来越迫切，因此通信协议就成为解决网络之间互联的关键技术。Keywords:interconnection

[,ɪntɚkə'nɛkʃən]n.[计]互连urgent

[ˈɜːdʒənt]adj.紧急的2-5ProtocolsLikeusingadifferentmotherlanguageneedacommonlanguagetotalkwitheachother,networkcommunicationalsoneedsakindofcommonlanguage,whichisacommunicationprotocol.Atpresent,thelocalareanetwork(LAN)thatiscommonlyusedinexternalprotocolsmainlyincludeNetBEUI,IPX/SPXanditscompatibleprotocolandTCP/IP.就像使用不同母语的人与人之间需要一种通用语言才能交谈一样，网络之间的通信也需要一种通用语言，这种通用语言就是通信协议。目前，局域网中常用的外部协议主要有NetBEUI、IPX/SPX及其兼容协议和TCP/IP三类。Keywords:compatible[kəm'pætɪb(ə)l]adj.兼容的2-5ProtocolsNetBEUI:NetBEUIagreement(NetBIOSExtendedUserInterface,UserextensionInterface)developedbyIBMin1985,itisasmallvolume,highefficiency,highspeedcommunicationprotocol.NetBEUI协议NetBEUI(NetBIOSExtendedUserInterface，用户扩展接口)由IBM于1985年开发完成，它是一种容量小、效率高、速度快的通信协议。Keywords:volume

['vɒljuːm]adj.大量的2-5ProtocolsTheearlyproductinMicrosoft,suchasDOS,LANManager,Windows3.xandWindowsforaWorkgroup,choosetheNetBEUIasacommunicationprotocol.Today,inthemainstreamproductsofMicrosoft,suchasWindowsXPandWindowsNT,NetBEUIhasbecomeitsinherentdefaultprotocol.微软在其早期产品，如DOS、LANManager、Windows3.x和WindowsforWorkgroup中主要选择NetBEUI作为自己的通信协议。在微软如今的主流产品，如WindowsXP和WindowsNT中，NetBEUI已成为其固有的缺省协议。Keywords:mainstream

['meɪnstriːm]n.主流inherent

[ɪn'hɪrənt]adj.固有的2-5ProtocolsIPX/SPXagreement:IPX/SPX(InternetworkPacketeXchange/SequencesPacketeXchange)isasetofcommunicationprotocolsfromNovell.TheobviousdifferencebetweenitandNetBEUIisthatIPX/SPXismuchlarger,andthatithasastrongadaptabilityincomplexenvironment.Butinthenon-Novellnetworkenvironment,generallytheIPX/SPXisnottobeused.IPX/SPX协议IPX/SPX(InternetworkPacketeXchange/SequencesPacketeXchange，网际包交换/顺序包交换)是Novell公司的通信协议集。与NetBEUI的明显区别是，IPX/SPX显得比较庞大，在复杂环境下具有很强的适应性。但在非Novell网络环境中，一般不使用IPX/SPX。2-5ProtocolsTCP/IPProtocol:TCP/IP(TransmissionControlProtocol/InternetProtocol)isoneofthemostcommonlyusedcommunicationprotocolscurrently,whichisageneralProtocolinthecomputerworld.InLAN,TCP/IPappearedonUnixsystemsatfirst,nowalmostallthemanufacturersandtheoperatingsystemsupportit.TCP/IP协议TCP/IP（TransmissionControlProtocol/InternetProtocol，传输控制协议/网际协议）是目前最常用到的一种通信协议，它是计算机世界里的一个通用协议。在局域网中，TCP/IP最早出现在Unix系统中，现在几乎所有的厂商和操作系统都开始支持它。Keywords:manufacturer[,mænju'fæktʃərɚ]n.制造商2-5ProtocolsAtthesametime,itisalsothefoundationprotocoloftheInternet.TCP/IPhasahighflexibilitytosupportnetworkofanysize,andalmostalloftheserversandtheworkstationscanbeconnected.Butitsflexibilityisalsobroughtalotofinconvenienceforusingit,andtheTCP/IPprotocolneedtobesetcomplicatedconfigurationbeforeused.同时，TCP/IP也是Internet的基础协议。TCP/IP具有很高的灵活性，支持任意规模的网络，几乎可连接所有的服务器和工作站。但其灵活性也为它的使用带来了许多不便，TCP/IP协议在使用时首先要进行复杂的设置。Keywords:flexibility

[,fleksɪ'bɪlɪtɪ]n.灵活性，适应性configuration[kən,fɪɡjə'reʃən]n.配置2-5ProtocolsEachnodeneedsone"IPaddress","subnetmask",a"defaultgateway"anda"hostname"atleast.However,WindowsNTprovidesatoolcalleddynamichostconfigurationprotocol(DHCP),whichcanautomaticallydistributetheinformationtotheclientforconnectingthenetwork,reducethenetworkburden,andavoidtheerror.每个节点至少需要一个“IP地址”、一个“子网掩码”、一个“默认网关”和一个“主机名”。不过，在WindowsNT中提供了一个称为动态主机配置协议（DHCP）的工具，它可自动为客户机分配连入网络时所需的信息，减轻了联网工作上的负担，并避免了出错。Expandedvocabulary:IPaddressIP地址subnetmask子网掩码defaultgateway默认网关hostname主机名OralpracticeQ:Howmanykindsofprotocoldoyouknow?A:Towkinds,theyare"internalagreement"and"externalagreement".Q:What’sthedifferentbetweenthem?A:Internalagreementsrarelyinvolvedinthenetwork,itismostlyusedforwebdevelopers,ifonlyyouwanttoformanetwork,justignoretheinternalagreement.Q:Howmanyexternalprotocolsdoyouknow?A:ExternalprotocolsmainlyincludeNetBEUI,IPX/SPXandTCP/IP.ExercisesShort-answerQuestions：1．Whatistheprotocolincomputer?2．PleaselistsevenlayersoftheOSI/RM?3．HowtosettheconfigurationaboutTCP/IP?4．Whichcommunicationprotocoliswidelyusedtoday?ExercisesTranslatethefollowingsentence