计算机专业英语 Unit 8 Computer Network Knowledge.ppt

1、Unit 8 Computer Network Knowledge,I. New Words,distributionn.分布，分配 distribute v. channeln.通道,信道 privatelyadv.私下地，秘密地 geographicadj地理的 scopen范围，广度 carriern.载体,搬运人,运载工具 configurationn.配置 network configuration 网络配置 layoutn.规划，(页面)布局，布置(图)；版面，(打印)格式； topologyn拓扑学，地志学 bus topology stracture 总线型拓扑结构 ring

2、topology stracture 环型拓扑结构 star topology stracture 星型拓扑结构 tree topology stracture 树型拓扑结构 mesh topology stracture 网状拓扑结构 cellular topology stracture 蜂窝拓扑结构 busn.总线 bus network 总线形网络 ringn.环 ring network 环形网络 token ring 令牌环,noden网络节点，连接到网络上的设备 multi-dropn多分支，多点（网络） multi-drop line 多分支 reservationn保留，保留

3、品 reserve v. inquiryv质询，探索 disadvantagen缺点 disabledadj.禁止的，屏蔽的，停用的，无效的 permissible adj. 允许的 detachv使分离，分遣 disturbv.扰动，干扰 personneln.人事部门 updatev更新 gatewayn网关 bridge 网桥,I. New Words,II. Phrases & Expressions,be classified as分为 communication channel通信信道 common carriers公用通信企业 refer to as称作 point-to-poi

4、nt点到点,III. Abbreviations,LAN （local area network）局域网 WAN （wide area network）广域网 WAN (metropolitan area network) 城域网,IV. Text Paragraph 1,Network establishes communication among computersThis system is especially helpful when people work in different placesIt improves the speed and accuracy of commun

5、ication，prevents messages from being misplaced and automatically ensures total distribution of key information 网络建立了计算机之间的通信。当人们在不同的地方工作时，网络是特别有用的。它提高了通信的速度和准确性，可防止信息被放错地方，且可自动确保关键信息的分发。,Par. 2,Networks A communication network is a collection of terminals，computers，and other equipments that use comm

6、unication channels to share data，information，hardware，and softwareNetworks can be classified as either local area networks or wide area networks 通信网络是由使用通信信道共享数据、信息、硬件和软件等的终端、计算机及其他设备组成的。网络可以分为局域网和广域网。,Par. 3,Local Area Networks （LANs） A local area networks，or LAN，is a communication network that is

7、privately owned and that covers a limited geographic area such as an office，a building，or a group of building 局域网(LAN)是专有的通信网络，它可以覆盖一个有限的地域，如一个办公室、一幢建筑或一群建筑等。,Par. 3,The LAN consists of a communication channel that connects either a series of computer terminals together with a minicomputer or，more c

8、ommonly，a group of personal computers to one anotherVery sophisticated LANs can connect a variety of office devices such as word processing equipment，computer terminals，video equipment and personal computers（See Fig8-1） 局域网是通过一个通信信道把一系列计算机终端连接到一台小型机上，更普遍的是把若干台个人计算机连接到一起而形成的。复杂的局域网可以连接各种办公设备，如字处理设备、计

9、算机终端、视频设备以及个人计算机等，如图8-1所示。,Par. 4,Two common applications of local area networks are hardware resource sharing and information resource sharingHardware resource sharing allows each personal computer on the network to access and use devices that would be too expensive to provide for each user1 Inform

10、ation resource sharing allows anyone using a personal computer on the local area network to access data stored on any other computer in the networkIn actual practice，hardware resource sharing and information resource sharing are often combined 局域网的两个基本应用是硬件资源共享和信息资源共享。硬件资源共享可使网上的每一台计算机访问并使用由于太昂贵而无法为

11、每人配备的设备；信息资源共享允许局域网上每一个计算机用户访问存储于网上其他计算机中的数据。在实际应用中，硬件资源共享和信息资源共享是常常结合在一起的。,Par. 5,Wide Area Networks （WANs） A wide area network，or WAN，is geographic in scope（as opposed to local） and uses telephone lines，microwaves，satellites，or a combination of communication channelsPublic wide area network compan

12、ies include so-called common carriers such as the telephone companies. Telephone company has encouraged a number of computers of companies to build their own wide area networks 广域网(WAN)相对于局域网，在覆盖的地理范围上要更大一些，它使用电话线、微波、卫星或这些通信信道的组合来传递信息。公共的广域网公司包括所谓的电信公司(如电话公司)。电话公司往往会鼓励很多公司去组建其自己的广域网。,Par. 6,Network

13、Configuration The configuration，or physical layout，of the equipment in a communication network is called topologyCommunication networks are usually configured in one or a combination of three patternsThese configurations are star，bus，and ring networksAlthough these configurations can be used with wi

14、de area networks，we illustrate them with local area networks Devices connected to a network，such as terminal，printers，or other computers，are referred to as nodes 通信网中设备的配置(或称物理布置)称为拓扑。通信网络通常被配置为三种模式中的一种或它们的组合。这些配置是星形、总线型和环形网络。虽然这些配置也可用于广域网，但在此仅在局域网中对它们进行说明。连接到网络上的设备，如终端、打印机或其他计算机，称为节点。,Par. 7,Star N

15、etwork A star network（Fig 8-2 ）contains a central computer and one or more terminals or personal computers connected to it，forming a starA pure star network consists of only point-to-point lines between the terminals and the computer, but most star networks, such as the one shown in Fig 8-2, include

16、 both point-to-point lines and multi-drop lines 星形网络由一台中央计算机(主机)和一台以上连接到该中央计算机上并形成星形结构的终端或计算机组成。纯粹的星形网络仅由终端和中央计算机之间两点的连线组成，但是大多数星形网络，如图8-2所示，由两点的连线和多条分叉线组成。,Par. 7,A star network configuration is often used when the central computer contains all the data required to process the input from the termin

17、als，such as an airline reservation system2For example, if inquiries were being processed in the star network，all the data to answer the inquiry would be contained in the database stored on the central computer 星形网络配置通常用于中央计算机中含有处理来自终端输入请求所需要的全部数据的场合，如航空订票系统。如果查询是在星形网络上处理的，那么回答该查询所需的所有数据应该包含在存储于中央计算机

18、的数据库中。,Par. 8,A star network can be relatively efficient，and close control can be kept over the data processed on the networkIts major disadvantage is that the entire network is dependent on the central computer and the associated hardware and softwareIf any of these elements fail，the entire network

19、 is disabled. Therefore, in most large star networks, backup computer systems are available in case the primary system fails 星形网络效率相对较高，严密的控制可保证网上数据的安全。其主要缺点是整个网络都依赖于中央计算机及其相关的硬件和软件，如果其中任何部分不能正常工作，整个网络就会瘫痪。所以，在大多数大型的星形网络中，都有一个备用的计算机系统，以防止主系统出现故障。,Par. 9,Bus Network When a bus network is used，all the

20、 devices in the network are connected to a single cableInformation is transmitted in either direction from any one personal computer to anotherAny message can be directed to specific device 使用总线型网络时，网络中的所有设备都通过同一根电缆连接到一起。信息可以从任何一台个人计算机向任何方向传给另一台计算机，任何信息都可以被传送到某一具体设备。,Par. 9,An advantage of the bus n

21、etwork is that devices can be attached or detached from the network at any point without disturbing the rest of the networkIn addition，if one computer on the network fails， this does not affect the other users of the networkFig 8-1 illustrates a simple bus network 总线型网络的优点是设备可以从任何一点连接到网络，或从网络的任何一点取下

22、，而不会影响网络其他部分的工作。此外，如果网络上的某台计算机出现故障，不会影响网络上其他用户。图81所示为一个简单的总线型网络。,Par. 10,Ring Network A ring network does not use a centralized host computerRather，a circle of computers communicate with one another（ Fig8-3 ） A ring network can be useful when the processing is not done at a central site， but at loca

23、l sites For example， computers could be located in three departments： accounting，personnel，and shipping and receiving 环形网络不使用中央计算机，而是连接成一个环形来实现计算机之间的相互通信，如图83所示。当数据处理不是在中心位置而是在当地进行时，环形网络是非常有用的。例如计算机可以放在三个部门：财务部、人事部和收发部。,Par. 10,The computers in each of these departments could perform the processing

24、required for each of the departments3On occasion，however， the computer in the shipping and receiving department could communicate with thecomputer in the accounting department to update certain data stored on the accounting department computer . 这三个部门的计算机可以分别完成各部门所要求的处理。但是收发部门的计算机偶尔需要与财务部门的计算机通信，以修改

25、存储在财务部计算机上的某些数据。,Par. 11,Data travels around a ring network in one direction only and passes through each node4Thus， one disadvantage of a ring network is that if one node fails， the entire network fails because the data does not get past the failed nodeAn advantage of a ring network is that less ca

26、ble is usually needed and therefore network cabling cost is lower 数据只能沿着环形网络的一个方向顺序通过每个节点进行传送。因此，环形网络的缺点是：如果一个节点出现故障，由于数据不能通过出现故障的节点，就会使整个网络无法工作。环形网络的优点是所需的电缆线少，因此，网络的电缆费用较低。,Par. 12,Connecting Networks Sometimes you might want to connect separate networkYou can do this by using gateways and bridges

27、A gateway is a combination of hardware and software that allows users on one network to access the resources on a different type of networkFor example，a gateway could be used to connect a local area network of personal computers to a mainframe computer networkA bridge is a combination of hardware an

28、d software that is used to connect similar networks 有时你可能想把许多独立的网络连接起来，可以通过使用网关或网桥来实现。网关由允许一个网络上的用户访问另一个不同类型网络上资源的软件和硬件组成。例如，可以用网关把一个由个人计算机组成的局域网和一个由大型计算机组成的网络连接起来。网桥由用于连接网络的软件和硬件组成。,Par. 12,For example， if a company had similar but separate local area networks of personal computers in their account

29、ing and marketing departments，the networks could be connected with a bridgeIn this example， using a bridge makes more sense than joining all the personal computer together in one large network because the individual department only occasionally needs to access information on the other network 例如，某公司

30、在其财务部和市场部各有一套由个人计算机组成的相似但又相互独立的局域网，这两个网络就可通过网桥连接起来。在这个例子中，使用网桥把两个网络连接到一起比把所有计算机连接起来组成一个大的网络要更加明智一些，因为每个部门仅仅偶尔需要访问另一个网络上的信息。,V. Exercises:,IDecide whether the following statements are true (T) or false (F) in relation to the information in the text： 1When a start network is used, all the devices in t

31、he network are connected to a single cable. 2A ring network use a centralized host computer. 3Networks can be classified as either local area networks or wide area networks. 4Two common applications of local area networks are hardware resource sharing and information resource sharing. 5Communication

32、 networks are usually configured in one or a combination of three patterns. 6An advantage of a bus network is that it needs less cable. 7One disadvantage of a ring network is that if one node fails, the entire network fails because the data does not get past the failed node. 8A gateway could be used

33、 to connect a local area network of personal computers to a mainframe computer network.,V. Exercises:,IITranslate the following terms or phrases from English into Chinese and vice versa： 1LAN6点对点 2WAN7通信信道 3star network8网络配置 4Broadband connection9数据网 5Multi-drop line10网桥,V. Exercises:,IIIChoose the best answers according to the text. 1When a ( ) is used, all the devices in the network are connected to a sing