教学材料《计算机》-2-1 Local area network

2-1LocalareanetworkIntroduction:Nowpeople'slivesbecomeincreasinglydependentonthenetwork,Wecanreadthenewsandknowtheworldthroughthenetwork.Thereareallkindsofnetworkinourlife,suchastransportationnetwork,telecommunicationnetwork,televisionnetwork,electricitynetwork,postalnetworketc..导读：现在人的生活越来越离不开网络，通过网络我们可以读新闻、知天下。我们的生活中有各种各样的网络，如交通网、通信网、电视网、电力网、邮政网等。Expandedvocabulary:telecommunication[ˌtelɪkəˌmju:nɪ'keɪʃn]n.电信；电通信2-1LocalareanetworkLocalAreaNetwork(LAN)isacomputernetworkcoveringonlyasmallphysicalarea,likeahome,anoffice,orasmallgroupofbuildings.Itsgeographicalscopeisbetween10mand1kmandthetransmissionrateisusuallyfrom1Mbpsto20Mbps.局域网的地理范围小，分布在诸如一个家庭、一个办公室或小建筑群。通常，它的地域范围在10～1000M之间，传输率在1～20Mbps之间。Expandedvocabulary:physical[ˈfɪzɪkl]adj.物理的；物质的geographical[ˌdʒi:ə'græfɪkl]adj.地理学的，地理的scope[skəʊp]n.范围；适用范围；作用域transmission[trænsˈmɪʃn]n.播送；传送；传输2-1LocalareanetworkThedefiningcharacteristicsofLANs,incontrasttoWANs,usuallyincludehigherdata-transferrates,smallerdistanceingeographicareasandlesscostintelecommunicationlines.和广域网相比较，局域网的特点是传输速度快、分布距离近、连接费用低。Expandedvocabulary:incontrastto与相反；与……形成对照；与……成对比2-1LocalareanetworkLANconsistsmainlyofnetworkhardwareandsoftware.Hardwaresystemsincludecomputers(severs,minicomputers,terminals),InterConnectionEquipments(ICEs),andtransmittingmedia.局域网中主要由网络硬件和网络软件组成。网络硬件系统包括计算机（服务器、小型机、终端）、互联设备和传输介质等。Keywords:minicomputers小型机terminal[ˈtɜ:mɪnl]n.终端；终点站interconnectionequipment互联设备transmittingmedia传输设备2-1LocalareanetworkThecomputeristhemainequipmentofnetwork,differentcomputersbeardifferenttasksinnetwork.Theserverisdesignedtoprovideservicestoclients.Itaffectstheoverallperformanceofthenetwork,whileaterminalisanelectromechanicalhardwaredevicethatisusedforenteringdatainto,anddisplayingdatafromacomputeroracomputingsystem.计算机是构成网络的主要设备，不同的计算机在网络中担负着不同的工作任务。服务器的作用是为客户提供服务，它影响网络的整体性能；而终端则是一台电子计算机或者计算机系统，用来让用户输入数据并显示计算结果的机器。Keywords:client[ˈklaɪənt]n.客户端；顾客；客户Expandedvocabulary:performance[pəˈfɔ:məns]n.性能；表演；演出；绩效electromechanical[ɪ'lektrəʊmɪ'kænɪkəl]adj.电动机械的，机电的，电机的2-1LocalareanetworkYoucanmanuallyconfiguretheIPaddressforthePC，YoucanalsoautomaticallyassignanappropriateaddressviaDynamicHostConfigurationProtocol(DHCP)foreachhost.可以通过手动方式为pc机配置IP地址，也可以通过动态主机配置协议（DHCP）为各主机自动分配一个合适的地址。Keywords:assign[əˈsaɪn]vt.分派，指定；指派；(过去式：assigned过去分词：assigned现在分词：assigning第三人称单数：assigns)Expandedvocabulary:appropriate[əˈprəʊpriət]adj.适当的；恰当的；合适的v.盗用；侵吞(过去式：appropriated过去分词：appropriated现在分词：appropriating第三人称单数：appropriates)2-1LocalareanetworkICESareusedtoconnectdifferentcomputersornetwork-relatedaccessories,suchasnetworkinterfacecards,integrateddevices,switches,repeaters,routers,modems.互联设备是用于连接网络中不同计算机或者网路的相关配件，主要包括网络接口卡、集线器、交换机、中继器、路由器、调制解调器等。Keywords:accessories[ək'sesərɪz]n.(accessory的名词复数)

附属设备；配件的2-1LocalareanetworkTherearemanydifferenttypesofLANs,EthernetsbeingthemostcommonforPCs.EachLANhasitsownuniquetopology(thegeometric

arrangementofdevicesonanLAN),orgeometricarrangement.Picturesbelowshowthreebasictopologies:bus,ring,andstar:有多种不同类型的局域网。以太网是PC机最常使用的一种。每一个局域网都有它自己的拓扑结构或几何分布。图1为三种基本的拓扑结构：总线型、星型以及环形：Keywords:Ethernet[ˈi:θənet]n.以太网；以太网络topology[tə'pɒlədʒɪ]n.拓扑结构；拓扑bus总线型star星型Expandedvocabulary:geometric[ˌdʒi:əˈmetrɪk]adj.几何学的；几何体arrangement[əˈreɪndʒmənt]n.安排；排列；布置2-1LocalareanetworkInbusnetworktopology,eachcomputerorserverisconnectertothesinglebuscablethroughsomekindofconnector.Inlocalareanetworkswherethestartopologyisused,eachmachineisconnectedtoacentralhub.Incontrasttothebustopology,thestartopologyallowseachmachineonthenetworktohaveapointtopointconnectiontothecentralhub.在总线拓扑结构中，可以通过一些连接器将每台计算机或服务器连接到单总线电缆。通常，星型拓扑结构用在局域网中。在这种结构中，网络中的每台机器通过中央集线器进行连接。Keywords:cable电缆hub集线器Expandedvocabulary:connecter[kə'nektə]n.连结者，连结物2-1LocalareanetworkInringnetworktopology,eachcomputerisconnectedtothenetworkinaclosedlooporring.Eachmachineorcomputerhasauniqueaddressthatisusedforidentificationpurpose.Thesignalpassesthrougheachmachineorcomputerconnectedtotheringinonedirection.Tokenringisthemostfamousringnetworktopology.在环型拓扑结构中，每台计算机连接到闭合环路。每一台机器或计算机都有一个唯一的识别地址。信号通过每台计算机按单一方向流动。令牌环是最著名的环形拓扑结构。Keywords:ring环形Expandedvocabulary:identification[aɪˌdentɪfɪˈkeɪʃn]n.识别；认同；鉴别；标识OralpracticeQ:Whatareyoudoingnow?A:Iamoninternet.Q:Isthatinteresting?A:Surely,youcanfindalotofthingsonit.Q:Whatdoseinternetusedfor?A:Icanuseittomakefriends,watchmoviesorshopping.Q:Howamazingitis!A:Yes,youcantryityourself.ExercisesChoices：1．____isusedtocommunicatewithanothercomputerovertelephonelines.A．keyboardB．modemC．mouseD．Printer2.Alicereceivedaninvitationfromherboss,

cameasasurprise.A．itB．thatC．whichD．He3.Theweatherturnedouttobeverygood,

wasmorethanwecouldexpect.A．whatB．whichC．thatD．itExercises4.Idon'tlike______asyouread.A.thenovelsB.thesuchnovelsC.suchnovelsD.samenovels5.Thisisoneofthebestfilms_______.A.thathavebeenshown