计算机英语 刘艺 王春生 第4版

支持这类应用所需的基本软件，已经从简单的实用软件包发展成一个不断扩 展的网络软件系统，该系统提供了一个复杂的网络范围的基础结构。从某种 意义上说，网络软件正在演变成一个网络范围的操作系统。
Ⅰ. Network Classifications
A computer network is often classified as being either a local area network (LAN) , a metropolitan area network (MAN), or a wide area network (WAN). A LAN normally consists of a collection of computers in a single building or building complex. For example, the computers on a university campus or those in a manufacturing plant might be connected by a LAN. n 综合体，集合体
二、协议 为了网络可靠运行，确立进行网络活动所遵循的规则很重要。这类规则称 为协议。通过开发和采用协议标准，不同厂商制造的网络应用产品能够相互兼 容。因此，在联网技术的开发中，协议标准的开发是一个必不可少的过程。
Ⅱ. Protocols
As an introduction to the protocol concept, let us consider the problem of coordinating the transmission of messages among computers in a network. Without rules governing this communication, all the computers might insist on transmitting messages at the same time or might fail to relay messages when that assistance is required.
V. 转述、转播 n.帮助、援助、支持
作为对协议概念的介绍，让我们考虑在一个网络的计算机之间协调报文传 输的问题。如果没有控制这种通信的规则，所有的计算机就可能坚持同时传输 报文，或者在需要传递报文时而未能传递。
Ⅱ. Protocols
One approach to solving this problem is the token ring protocol, which was developed by IBM in the 1970s and continues to be a popular protocol in networks based on the ring topology. In this protocol, all the machines in the network transmit messages in only one common direction（Fig. 8A1）, meaning that all messages sent over the network move around the ring in the same direction by being forwarded from computer to computer.
As the simple terminals employed by these users grew into small computers themselves, a star network emerged. A point to emphasize is that the connections between machines in a network do not need to be physical. Wireless networks, using radio broadcast technology, are becoming quite common.
因特网属于开放式系统。尤其是，整个因特网的通信是由一组称为 TCP/IP协议组的开放标准来控制的。任何人都可以自由地使用这些标准，而 不需要付费或签署许可协议。
Ⅰ. Network Classifications
In contrast, a company such as Novell Inc. might develop systems for which it chooses to maintain ownership rights, allowing the company to draw income from selling or leasing these products. Networks based on such systems are examples of closed networks.
on the contrary
相反，像Novell股份有限公司这样的公司可能选择为其开发的系统保留所有 权，允许公司通过出售或出租这些产品获得收入。基于这类系统的网络属于 封闭式网络的例子。
Ⅰ. Network Classifications
Still another way of classifying networks is based on the topology of the network, which refers to the pattern in which the machines are connected. The bus topology, ring topology, and star topology are three popular topologies. Of these, the star network is perhaps the oldest, having evolved from the paradigm of a large central computer serving many users.
随着这些用户所使用的简单终端本身发展成小型计算机，星形网络也就出现 了。需要强调的一点是，在一个网络中，计算机之间的连接并不一定是物理 连接。使用无线广播技术的无线网络正在变得相当常见。
Ⅱ. Protocols
指导、实施、处理
For a network to function reliably, it is important to establish rules by which network activities are conducted. Such rules are called protocols. By developing and adopting protocol standards, venders are able to build products for network applications that are compatible with products from other venders. Thus, the development of protocol standards is an indispensable process in the development of networking technologies.
在不同计算机之间共享信息和资源的需要，导致了相互连接的计算机系 统的产生。这种相互连接的计算机系统被称为网络。在网络中，计算机连接 在一起，从而数据可以从一台计算机传输到另一台计算机。在网络中，计算 机用户可以交换信息，并共享分散在整个网络系统的资源，如打印能力、软 件包以及数据存储设备。
The underlying software required to support such applications has grown from simple utility packages into an expanding system of network software that provides a sophisticated network wide infrastructure. In a sense, network software is evolving into a network wide operating system.
从...逐渐形成（发展成）
还有一种网络分类方法，它基于网络的拓扑结构，即计算机相互连接的模式。 总线拓扑结构、环形拓扑结构和星形拓扑结构是3种流行的拓扑结构。其中，星 形网络或许是最古老的，这种网络由一台大型中央计算机服务许多用户的范式演 变而来。
Ⅰ. Network Classifications
Unit 8 Computer Network
Section A Network Fundamentals
The need to share information and resources among different computers has led to linked computer systems, called networks, in which computers are connected so that data can be transferred from machine to machine. In these networks, computer users can exchange messages and share resources such as printing capabilities, software packages, and data storage facilities-that are scattered throughout the system.
城域网属于中型网络，如一个覆盖某一社区的网络。广域网连接地理范围更广 的计算机，这些计算机或许在相邻的城市，或许在地球相反的两面。
Ⅰ. Network Classifications
Another means of classifying networks is based on whether the network's internal operation is based on designs that are in the public domain or on innovations owned and controlled by a particular entity such as an individual or a corporation. A network of the former type is called an open network; a network of the latter type is called a closed, or sometimes a proprietary network.
adj. 复杂的、难懂的、合成的
一、网络分类 计算机网络常常划分为局域网、城域网和广域网。局域网通常由一幢建筑 物或一个建筑群中的若干计算机组成。例如，大学校园里的计算机或制造工厂 中的计算机可以用局域网连接。
n 植物、工厂、机械设备
Ⅰ. Network Classifications
A MAN is a netwoຫໍສະໝຸດ Baiduk of intermediate size, such as one spanning a local community. A WAN links machines over a greater distance — perhaps in neighboring cities or on opposite sides of the world.
网络分类的另一种方式是根据网络的内部运行是基于无专利权保护的设计 还是基于特定实体（如个人或公司）所拥有和控制的革新。前一种类型的网络 称为开放式网络，后一种类型的网络称为封闭式网络，有时也称为专有网络。
Ⅰ. Network Classifications
The Internet is an open system. In particular, communication throughout the Internet is governed by an open collection of standards known as the TCP/IP protocol suite. Anyone is free to use these standards without paying fees or signing license agreements.