注：今天时间不多，所以没来得及对潘老师的翻译，在此作为交流，勿仿！
1.1 Uses of Computer Networks

Before we start to examine the technical issues in detail, it is worth devoting some time to pointing out why people are interested in computer networks and what they can be used for. After all, if nobody were interested in computer networks, few of them would be built. We will start with traditional uses at companies and for individuals and then move on to recent developments regarding mobile users and home networking.

1.1计算机网络的使用15.30

在我们详细探讨技术问题之前，有必要花点时间来解释，为什么人们对计算机网络有着浓厚的兴趣，计算机网络可以用来做些什么。毕竟，如果没有人对计算机网络感兴趣，这门学科也很难建立起来。首先，我们将介绍计算机网络在公司及对个人的传统用法；然后，介绍在移动用户及家庭网络方面近来的发展。

1.1.1 Business Applications

Many companies have a substantial number of computers. For example, a company may have separate computers to monitor production, keep track of inventories, and do the payroll. Initially, each of these computers may have worked in isolation from the others, but at some point, management may have decided to connect them to be able to extract and correlate information about the entire company.

1.1.1商业软件

许多公司拥有很大数量的计算机。例如，一家公司已经把计算机分配到控制生产，跟踪库存及计算薪资等不同的职能中。最初，每台计算机可能执行与其他计算机不同的功能，但是在某些方面，出于管理的需要，必须把他们连接起来从中提取对整个公司有用的信息，并使这些信息相互关联。

Put in slightly more general form, the issue here is resource sharing, and the goal is to make all programs, equipment, and especially data available to anyone on the network without regard to the physical location of the resource and the user. An obvious and widespread example is having a group of office workers share a common printer. None of the individuals really needs a private printer, and a high-volume networked printer is often cheaper, faster, and easier to maintain than a large collection of individual printers.

把它看作更为一般的形式，这里的问题即是如何实现资源共享，目标是使所有的程序，设备，特别是数据能为网络上所有人所用。资源共享的一个很明显且大家所熟知的例子是共享打印机，办公室里的所有员工共用一台打印机。单个人确实没必要用私人打印机。通常，一台大容量网络打印机比一大群的个人打印机价格上更便宜，速度更快，也更容易维护。

However, probably even more important than sharing physical resources such as printers, scanners, and CD burners, is sharing information. Every large and medium-sized company and many small companies are vitally dependent on computerized information. Most companies have customer records, inventories, accounts receivable, financial statements, tax information, and much more online. If all of its computers went down, a bank could not last more than five minutes. A modern manufacturing plant, with a computer-controlled assembly line, would not last even that long. Even a small travel agency or three-person law firm is now highly dependent on computer networks for allowing employees to access relevant information and documents instantly.

然而，比共享诸如打印机、扫描仪和CD播放器等设备资源更重要的也许是信息共享。每家大型和中型企业及许多小公司在很大程度上依赖于计算机化的信息。大部分公司有客户记录、库存状态、应收帐款、财务报表、税收信息及其他更多的联网信息。假如所有的计算机停止工作，银行不到五分钟就会倒闭；而即使是一家拥有计算机控制生产线的现代制造型工厂，也不会持续太长时间。如今，甚至一家小旅行社或者三个人的法律公司也高度依赖计算机网络，以使员工快速获得相关信息和文件。

For smaller companies, all the computers are likely to be in a single office or perhaps a single building, but for larger ones, the computers and employees may be scattered over dozens of offices and plants in many countries. Nevertheless, a sales person in New York might sometimes need access to a product inventory database in Singapore. In other words, the mere fact that a user happens to be 15,000 km away from his data should not prevent him from using the data as though they were local. This goal may be summarized by saying that it is an attempt to end the ''tyranny of geography.''

就一些小公司而言，所有的计算机可能放在一间办公室或者在一栋楼里；但对大公司来说，计算机和员工可能分散在许多国家的几十个办公室或工厂里。