英语翻译Throughout the book we will use the term ''computer netw

英语翻译
Throughout the book we will use the term ''computer network'' to mean a collection of autonomous computers interconnected by a single technology.Two computers are said to be interconnected if they are able to exchange information.The connection need not be via a copper wire; fiber optics,microwaves,infrared,and communication satellites can also be used.Networks come in many sizes,shapes and forms,as we will see later.Although it may sound strange to some people,neither the Internet nor the World Wide Web is a computer network.By the end of this book,it should be clear why.The quick answer is:the Internet is not a single network but a network of networks and the Web is a distributed system that runs on top of the Internet.
There is considerable confusion in the literature between a computer network and a distributed system.The key distinction is that in a distributed system,a collection of independent computers appears to its users as a single coherent system.Usually,it has a single model or paradigm that it presents to the users.Often a layer of software on top of the operating system,called middleware,is responsible for implementing this model.A well-known example of a distributed system is the World Wide Web,in which everything looks like a document (Web page).
In a computer network,this coherence,model,and software are absent.Users are exposed to the actual machines,without any attempt by the system to make the machines look and act in a coherent way.If the machines have different hardware and different operating systems,that is fully visible to the users.If a user wants to run a program on a remote machine,he has to log onto that machine and run it there.
In effect,a distributed system is a software system built on top of a network.The software gives it a high degree of cohesiveness and transparency.Thus,the distinction between a network and a distributed system lies with the software (especially the operating system),rather than with the hardware.
Nevertheless,there is considerable overlap between the two subjects.For example,both distributed systems and computer networks need to move files around.The difference lies in who invokes the movement,the system or the user.Although this book primarily focuses on networks,many of the topics are also important in distributed systems.For more information about distributed systems.

整本书中,我们将使用术语'计算机网络'意思是一个集自主计算机互联的一种 单一的技术.两台电脑说是相互联系,如果他们能够交换信息.连接不必经由铜线; 光纤,微波,红外,卫星通信也可使用.网络有许多大小形状和形式,正如我们稍后会看到.虽然听起来奇怪,对某些人而言,既不上网也不万维网是一个计算机网络.到本世纪末,书籍,应该很清楚为什么.快速回答的问题是:互联网不是一个单一的网络,而是网络和网络是一个分布式系统 上运行的因特网.有相当大的混乱,在文献之间的计算机网络和分布式系统.关键的区别是,在分布式系统中,收集独立的计算机,似乎它的用户作为一个统一的系统.通常,它有一个单一的模式或范例,它呈现给用户.往往一层软件之上的操作系统,称为中间件,是负责实施这一模式.一个著名的例子一个分布式系统是万维网,在这一切活像一个文件(网页) .在一个计算机网络,这种一致性,模型和软件都缺席.用户所接触到的实际机器 没有任何试图通过制度建设,使机器的外观和行为一致的方法.如果机器有不同的硬件和不同的操作系统,这是十分明显的用户.如果用户想要运行程序在远端机 他登录到该机器上运行.实际上,一个分布式系统是一个软件系统之上建造一个网络.该软件为它提供了高度的凝聚力和透明度.因此,区分网络和分布式系统的关键在软件(尤其是操作系统) ,而非硬件.不过,现在有相当大的重叠两个科目.例如,分布式系统和计算机网络需要移动文件左右.不同之处在于谁援引运动,系统或用户.虽然这本书主要侧重网络,很多议题也是很重要的分布式系统.更多关于分布式系统.