通信英语 第三单元

通信英语
The early development of LANs, and WANs was chaotic（混乱的） in many ways. the early 1980s saw tremendous （极大的） increases in the numbers and sizes of networks. As companies 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.
• 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 different 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.
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Hale Waihona Puke Baidu体验
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到了80年代中期，这些公司开 始经历由于他们扩张网络所带 来的不断的麻烦。采用不同的 规范和实现的网络不能够相互 通信。他们认识到，他们需要 离开专用的联网系统。
通信英语
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Proprietary systems are privately developed, owned, and controlled. in the computer industry, proprietary is the opposite of open. Proprietary means 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.
proprietary [prə`praiətəri] 专有的、私有
的 Private [praivit] 私人的 、私有的
Opposite n. 对立面、相反的
专用系统是指那些被私人开 发、拥有和控制的网络。在 计算机行业，专用是开放的 反义词。专用意味着一个公 司或一小群公司完全控制着 技术的使用和发展。而开放 却意味着技术可为整个公众 所利用。
通信英语
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The 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 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, even if the sender and the receiver have different types of network media.
通信英语
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The OSI reference model is the primary model基本模 型 for network communications. A primary objective of the OSI reference model is to accelerate the development of future networking products联网产品. Although there are other models in existence, most network vendors网络供应商 today relate their products to the OSI reference model, especially when they want to educate users on the use of their products. They consider it the best tool available to teach people about sending and receiving data on a network.
通信英语
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通信英语
Key Terms Review
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ASCII American Standard Code for Information Interchange Expansion slots 扩展槽 Socket 插座 Integrated circuits 集成电路 IC Card storage 存储器 Terminal 终端 Port 接口 端口 Media 媒体 媒介 介质 Multimedia 多媒体 Device 设备 RAM 随机存储器 Magnetic strip Card ROM 只读存储器 Secondary storage 外存 Host/Terminal 主机/终端 Memory 内存
通信英语
– vendor n. 卖主，供应商 • buyer n. 买主 – framework n. 框架 – packet n. 包，分组 • data packet 数据包 – layer n. 层 – component n. 部件，组件 – synchronize vt. 使同步 – browser n. 浏览器 • an Internet browser 因特网浏览器 – format n. 格式
通信英语
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In the OSI reference model, there are seven numbered 编号的 layers. Each layer illustrates表示 a particular network function网络功能. This separation分离，分解 of networking functions联网功能 is called layering分 层. Dividing the network into these seven layers provides the following advantages:
通信英语
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To 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 set 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.
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局域网、城域网和广域网的发 展在很多方面都是混乱无序的， 80年代初，网络的规模和数量 发展极快，由于公司意识到， 利用联网技术，他们可以省钱 和提高生产率，因而只要能引 入新的网络技术和产品，他们 就要扩充现有的网络和添加新 的网络。
通信英语
By 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 to move away from proprietary networking systems.
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通信英语
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– compression n. 压缩 • compress vt. 压缩 to compress a file 压缩一个文件 press a button 按一个按钮 • compressed air 压缩空气 an air-compressor 空压机 – encryption n. 加密 – protocol n. 协议 – frame n. 帧，框架 – access n. 接入，连通 – topology n. 拓扑
Binary/Octet/Decimal/Hex 二进制/八进制/十进制/十六进制
通信英语
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– network v. 联网 n. 网络 networking technology 联网技术 – specification n. 规格，规范 technical specifications 技术规格 – compatible a. 一致的，兼容的，匹配的 This software is compatible with Window XP. 这套软件 和Window XP兼容。 – scheme n. 方案，设计，方法 – model n. 模型，模范，模特儿 pattern n. 样式，模式 mode n. 模式，方式
通信英语
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The ISO reference model, released in 1984, was the descriptive scheme they created. it provided 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.
通信英语
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Break … into 把…打碎成 multiple-vendor 多个供应商 prevent … from 阻止 它将网络分成更小的、更 简单的部分，这些部分更 容易发展。它简化了网络 部件的标准化，允许多个 供应商开发与支持。它允 许不同类型的网络软件和 硬件相互通信。它防止一 层的变化影响其他的层次， 从而使得各层更快的进行 开发。它把通信部分分成 更小的部分，从而更容易 理解。