通信英語 第三單元

1、通信英語 unit 3通信英語 unit 3Key Terms ReviewASCII American Standard Code for Information Interchange Expansion slots 擴展槽Integrated circuits 集成電路 Memory內(nèi)存storage 存儲器Socket 插座Media 媒體 媒介 介質(zhì)Port 接口 端口Device 設(shè)備ROM 只讀存儲器RAM 隨機存儲器Multimedia 多媒體IC CardMagnetic strip CardSecondary storage 外存Terminal 終端Host/Termin

2、al 主機/終端Binary/Octet/Decimal/Hex 二進制/八進制/十進制/十六進制 通信英語 unit 3 network v. 聯(lián)網(wǎng) n. 網(wǎng)絡(luò) networking technology 聯(lián)網(wǎng)技術(shù) specification n. 規(guī)格，規(guī)范 technical specifications 技術(shù)規(guī)格 compatible a. 一致的，兼容的，匹配的 This software is compatible with Window XP. 這套軟件和Window XP兼容。 scheme n. 方案，設(shè)計，方法 model n. 模型，模范，模特兒 pattern n. 樣

3、式，模式 mode n. 模式，方式通信英語 unit 3 vendor n. 賣主，供應(yīng)商 buyer n. 買主 framework n. 框架 packet n. 包，分組 data packet 數(shù)據(jù)包 layer n. 層 component n. 部件，組件 synchronize vt. 使同步 browser n. 瀏覽器 an Internet browser 因特網(wǎng)瀏覽器 format n. 格式通信英語 unit 3 compression n. 壓縮 compress vt. 壓縮 to compress a file 壓縮一個文件 press a button 按一個

4、按鈕 compressed air 壓縮空氣 an air-compressor 空壓機 encryption n. 加密 protocol n. 協(xié)議 frame n. 幀，框架 access n. 接入，連通 topology n. 拓撲通信英語 unit 3The early development of LANs, and WANs was chaotic（混亂的） in many ways. the early 1980s saw tremendous （極大的） increases in the numbers and sizes of networks. As companies

5、 realized they could save money and gain productivity by using networking technology, they added networks and expanded existing networks almost as rapidly as new network technologies and products could be introduced.局域網(wǎng)、城域網(wǎng)和廣域網(wǎng)的發(fā)展在很多方面都是混亂無序的，80年代初，網(wǎng)絡(luò)的規(guī)模和數(shù)量發(fā)展極快，由于公司意識到，利用聯(lián)網(wǎng)技術(shù)，他們可以省錢和提高生產(chǎn)率，因而只要能引入新的網(wǎng)

6、絡(luò)技術(shù)和產(chǎn)品，他們就要擴充現(xiàn)有的網(wǎng)絡(luò)和添加新的網(wǎng)絡(luò)。 Paragraph 1 通信英語 unit 3By the mid-1980s, theses companies began to experience growing pains from all the expansions they made. It became harder for networks that used different specifications and implementations（方法） to communicate with each other. They realized that needed

7、 to move away from proprietary networking systems. 體驗到了80年代中期，這些公司開始經(jīng)歷由于他們擴張網(wǎng)絡(luò)所帶來的不斷的麻煩。采用不同的規(guī)范和實現(xiàn)的網(wǎng)絡(luò)不能夠相互通信。他們認識到，他們需要離開專用的聯(lián)網(wǎng)系統(tǒng)。 Paragraph 2 通信英語 unit 3Proprietary systems are privately developed, owned, and controlled. in the computer industry, proprietary is the opposite of open. Proprietary mean

8、s that one or a small group of companies controls all usage and evolution of the technology. Open means that free usage of the technology is available to the public. Paragraph 3 專用系統(tǒng)是指那些被私人開發(fā)、擁有和控制的網(wǎng)絡(luò)。在計算機行業(yè)，專用是開放的反義詞。專用意味著一個公司或一小群公司完全控制著技術(shù)的使用和發(fā)展。而開放卻意味著技術(shù)可為整個公眾所利用。 proprietary prpraitri 專有的、私有的Priv

9、ate praivit 私人的 、私有的Opposite n. 對立面、相反的 通信英語 unit 3To address the problem of different network systems being incompatible and incapable of communicating with each other, the international Organization for Standardization (ISO) researched network schemes, such as DECnet, SNA, and TCP/IP, to find a se

10、t of rules. as a result of this research, the ISO created a network model that could help vendors create networks that would be compatible with, and interoperate with, other networks. Paragraph 4 通信英語 unit 3The ISO reference model, released in 1984, was the descriptive scheme they created. it provid

11、ed vendors with a set of standards that could enable greater compatibility and interoperability between the various type networks technologies that were produced by many companies around the world.Paragraph 5 通信英語 unit 3The OSI reference model is the primary model基本模型 for network communications. A p

12、rimary objective of the OSI reference model is to accelerate the development of future networking products聯(lián)網(wǎng)產(chǎn)品. Although there are other models in existence, most network vendors網(wǎng)絡(luò)供應(yīng)商 today relate their products to the OSI reference model, especially when they want to educate users on the use of the

13、ir products. They consider it the best tool available to teach people about sending and receiving data on a network. Paragraph 6 通信英語 unit 3The OSI reference model allows you to view the network functions that occur at each layer. More importantly, the OSI reference model is a framework you can use

14、to understand how information travels throughout a network. In addition, the OSI reference model can be used to visualize how information, or data packets, travels from application programs, through a network medium, to other application programs that are located in another computer on a network, ev

15、en if the sender and the receiver have different types of network media. Paragraph 7 通信英語 unit 3In the OSI reference model, there are seven numbered編號的 layers. Each layer illustrates表示 a particular network function網(wǎng)絡(luò)功能. This separation分離，分解 of networking functions聯(lián)網(wǎng)功能 is called layering分層. Dividing

16、the network into these seven layers provides the following advantages:Paragraph 8 通信英語 unit 3 It breaks network communication into smaller, simpler parts that are easier to develop . It facilitates standardization of network components to allow multiple-vendor development and support. It allows diff

17、erent types of network hardware and software to communicate with each other. It prevents changes in one layer from affecting the other layers, so that they can develop more quickly. It breaks network communication into smaller parts to make learning it easier to understand. Break into 把打碎成multiple-v

18、endor 多個供應(yīng)商 prevent from 阻止 它將網(wǎng)絡(luò)分成更小的、更簡單的部分，這些部分更容易發(fā)展。它簡化了網(wǎng)絡(luò)部件的標準化，允許多個供應(yīng)商開發(fā)與支持。它允許不同類型的網(wǎng)絡(luò)軟件和硬件相互通信。它防止一層的變化影響其他的層次，從而使得各層更快的進行開發(fā)。它把通信部分分成更小的部分，從而更容易理解。 Paragraph 8 通信英語 unit 3Now lets take a look at each layer in the OSI reference model ,as shown in figure 3-1.通信英語 unit 3通信英語 unit 3The application

19、 layer is the OSI layer that is closest to the user. It provides network services, such as file access and printing, to the users application. It differs form the other layers in that it does not provide services to any other OSI layer, but rather, only to applications outside the OSI model. The app

20、lication layer established the availability of intended communication parters. It also synchronizes and establishes an agreement on procedures for error recovery and control of data integrity. If you want toRemember Layer 7 in as few words as possible,think of the browsers. 應(yīng)用層是OSI參考模型中離用戶最近的層，它為用戶的

21、應(yīng)用提供網(wǎng)絡(luò)服務(wù)，比如文件訪問和打印等。它與其他的層的區(qū)別在于，它不向OSI 的其他層提供服務(wù)，相反的，它僅向OSI參考模型之外提供服務(wù)，應(yīng)用層使得通信雙方成為可能。它還對糾錯和數(shù)據(jù)整合的過程同步并達成協(xié)議。如果你想簡單的用幾個詞記住第7層，記住瀏覽器即可。 Layer 7: The application Layer 通信英語 unit 3The presentation layer ensures that the information that the application layer of one system sends out is readable by the applic

22、ation layer of another system. If necessary, the presentation layer translates between multiple data formats by using a common format, this layer also is responsible for compression and encryption. If you want to think of layer 6 in as few words as possible, think of a common data format.Layer 6: Th

23、e presentation layerAs its name implies, the session layer establishes, manages, and terminates sessions between two communicating hosts. The session layer provides its services to the presentation layers and manages their data exchange. In addition to session regulation, the session layer offers pr

24、ovision for efficient data transfer, class of services, and exception reporting of session layer, presentation layer, and application layer problems, if you want to remember layer 5 in as few as possible, think of dialogues and conversations.Layer 5: The session layer通信英語 unit 3The four lower layers

25、 of the OSI model define how data is transferred across a physical wire through internetworking devices, to the desired end station, and finally to the application. Figure 2-3 summarizes the basic function of these four layers.The Lower Layers desired dizai 所請求的 Figure 2-3 （P.39）通信英語 unit 3Layer 4 :

26、The transport layerThe transport layer segments data from the sending hosts system and reassembles the data into a data stream on the receiving hosts system. the boundary between the transport layer and the session layer can be thought of as a boundary between application protocols and data-flow pro

27、tocols. Whereas the application, presentation, and session layers are concerned with application issues, the lower four layers are concerned with data transport issues.重新組裝 數(shù)據(jù)流 界線, 范圍 hwrz conj. 然而, 鑒于 與有關(guān) 通信英語 unit 3The transport layer attempts to provide a data transport service that shields the u

28、pper layers from transport implementation details. Specifically, such issue as how reliable transport between two hosts is accomplished in the concern of the transport layer. In providing communication service, the transport layer established, maintains, and properly terminates connection-oriented c

29、ircuits. In providing reliable service, transport error detection-and-recovery and information flow control are used. If you want to remember layer 4 in as few words as possible, think of the flow control and reliability. 傳輸層試圖提供數(shù)據(jù)傳輸服務(wù)，而將傳輸層的實現(xiàn)細節(jié)對高層進行屏蔽。而將較高層的傳輸實現(xiàn)的細節(jié)方面屏蔽。尤其應(yīng)該指出的是，在兩個主機之間數(shù)據(jù)傳送是否可靠之類的問

30、題是由傳輸層來考慮實現(xiàn)的。在提供通信服務(wù)時，傳輸層建立、維持和斷開面向連接的電路，在提供可靠服務(wù)的方面，傳輸層采用了傳輸誤碼檢測和恢復(fù)，以及信息流控制技術(shù)。 Shield 保護、遮蔽、屏蔽 實施; 實現(xiàn) 被完成 通信英語 unit 3The network layer is a complex layer that provides connectivity and path selection between host systems that might be located on geographically separated networks. If you want to reme

31、mber layer 3 in as few words as possible, think of path selection, routing, and logical addressing.Layer 3: the network layer 通信英語 unit 3The data link layer provides the transit of data across a physical link. In so doing, the data link layer is concerned with physical (as opposed to logical) addressing, network (sometimes called logical) topology, network media access, and error detection. If you want to remember layer 2 in as few words as possible, think of frames and media access control.Layer 2: the data link layer 通信英語 unit 3The physical layer defines