(完整版)本科生_毕业设计说明书外文文献及翻译_

Computer networking summarize

Networking can be defined as the linking of people, resources and ideas. Networking occurs via casual encounters, meetings, telephone conversation, and the printed words. Now the computer networking provide beings with new networking capabilities. Computer network are important for services because service tasks are information intensive. During the is transmitted between clients, coworkers, management, funding sources, and policy makers. Tools with rapidly speed up communication will dramatically affect services.

Computer network growing explosively. Two decades ago, few people essential part of our infrastructure. Networking is used in every aspect of business, including advertising, production, shipping, planning, bulling, and accounting. Consequently, most corporations in on-line libraries around the world. Federal, state, and local government offices use networks, as do military organizations. In short, computer networks are everywhere.

The growth in networking economic impact as well. An entire industry jobs for people with more networking expertise. Companies need workers to plan, acquire, install, operate, and manage the addition computer programming is no longer restricted to individual computers; programmers are expected to design and implement application software that can communicate with software on other computers.

Computer networks link computers by communication lines and software protocols, allowing data to be exchanged rapidly and reliably. Traditionally, they split between wide area networks (WANs) and local area networks (LANs). A WAN is a network connected over long-distance telephone lines, and a LAN is a localized network usually in one building or a group of buildings close together. The distinction, computers. Today networks carry e-mail, provide access to public databases, and are beginning to be used for distributed systems. Networks also allow users in one locality to share expensive resources, such as printers and disk-systems.

Distributed computer systems are built using networked computers that cooperate to perform tasks. In this environment, each part of the networked system does what it is best at. The of a personal computer or workstation provides a good user interface. The mainframe, on the other the results to the users. In a distributed environment, a user might use in a special language (e. g. Structured Query Language-SQL), to the mainframe, which then parrrses the query, returning the user only the data requested. The user might then use the data. By passing back the user’s PC only the specific information requested, network traffic is reduced. If the whole file were transmitted, the PC would then of one network to access the resources on a different type of network. For example, a gateway could be used to connect a local area network of personal computers to a mainframe computer network. For example, if a company this example, using a bridge makes more sense than joining all the

personal computers together in one large network because the individual departments only occasionally need to access information on the other network.

Computer networking technology can be divided into four major aspects.

The first is the data transmission. It explains that at the lowest level electrical signals traveling across wires are used to carry information, and shows be encoded using electrical signals.

The second focuses on packet transmission. It explains why computer network use packets, and shows . LANs and WANs discussed above are two basic network.

The third covers internetworking—the important idea that allows system, and TCPIP, the protocol technology used in global internet.

The fourth explains networking applications. It focuses on , and programs provide services such as electronic mail and Web browsing.

Continued growth of the global Internet is one of most interesting and exciting phenomena in networking. A decade ago, the Internet was a research project that involved a few dozen sites. Today, the Internet into a production communication system that reaches millions of people in almost all countries on all continents around the world. In the United States, the Internet connects most corporations, colleges and universities, as well as federal, state, and local government offices. It will soon reach most elementary,

junior, and senior addition, many private residences can reach the Internet through a dialup telephone connection. Evidence of the Internet’s impact on society can be seen in advertisements, in magazines and on television, which often contain a reference to an Internet Web site that provide additional information about the advertiser’s products and services.

A large organization with diverse networking requirements needs multiple physical networks. More important, if the organization chooses the type network that is best for each task, the organization will network can only communicate with other computers attached to same network. The problem became evident in the 1970s as large organizations began to acquire multiple networks. Each network in the organizations formed an island. In many early installations, each computer attached to a single network and employees employees was given access to multiple svreens and keyboards, and the employee was forced to move form one computer to another to send a massage across the appropriate network. Users are neither satisfied nor productive when they must use a separate computer. Consequently, most modern computer communication syetem allow communication between any two computers analogous to the way a telephone system provides communication between any two telephones. Known as universal service, the concept is a fundamental part of networking. With universal service, a user on any computer in any part of an organization can send messages or data to any other users. Furthermore, a user does not need to change computer systems when

changing tasks—all information is available to all computers. As a result, users are more productive.

The basic component used to commect organization to choose network technologies appropriate for each need, and to use routers to connect all networks into a single internet.

The goal of internetworking is universal service across an internet, routers must agree to forward information from a source on one network to a specified destination on another. The task is complex because frame formats and addressing schemes used by underlying networks can differ. As s resulrt, protocol software is needed on computers and routers make universal service possible. Internet protocols overcome differences in frame formats and physical addresses to make communication pissible among networks that use different technologies.

In general, internet software provides the appeatrance of a single, seamless communication system to which many computers attach. The syetem offers universal service :each computer is assigned an address, and any computer can send a packet to any other computer. Furthermore, internet protocol software —neither users nor application programs are a ware of the underlying physical networks or the routers that connect them.

We say that an internet is a virtual network system because the communication system is an abstraction. That is, although a combination of of a uniform network syetem, no such network exists.

Research on internetworking modern networking. In fact,

internet techmology . Most large organizations already use internetworking as primary computer communication mechanism. Smaller organizations and individuals are beginning to do so as well. More inportant, the TCPIP technology computers in schools, commercial organications, government, military sites and individuals in almost all countries around the world.

电脑网络简述

网络可被定义为人、资源和思想的联接。网络化可发生于偶然、会议、电话交谈以及印刷文字。今天，电脑网络向人类提供了新的网络化能力。电脑网络在人的服务中是十分重要的，这是因为人的服务工作强调于信息。在帮助人的过程中，信息在客户、合作人、管理层、资金提供机构和政策制定者之间传送。具备能使通讯速度迅速加快的工具，将极大的影响人的服务。

计算机网络已经爆炸性的增长。20年前，很少有人接触过电脑。现在计算机通信已成为我们社会的基础结构的关键部分。网络被用在商业的各个方面，包括广告、生产、装运、计划、付帐和记账等等。结果，大多数企业具有多种网络。学校，从小学到研究生的所有年级都在使用电脑网络，这些网络让同学和老师即时的查阅遍布全世界的联机图书馆中的信息。联邦、州和地方政府办公室如同军事组织一样使用网络。总之，计算机网无所不在。

网络的发展还有经济上的影响。一个完整的开发网络技术、产品和服务的产业已经出现。电脑网络的普及性和重要性产生了对具有网络专长人员的强势需求。企业要求工作人员进行计划、获取、安装、操作和管理包含计算机网络和因特网的硬件系统。而且，计算机编程不再受独立的计算

机所限制；程序员要能设计和实施能与其他电脑上的软件实现通信的应用软件。

电脑网络通过通信线和软件协议将计算机联接起来，允许数据快速可靠的进行交换。传统上的电脑网络被分为广域网（WANs）和局域网（LANs）,WAN网是通过长距离电话线连接起来的网络，而LAM通常是在一建筑物或一群相邻的建筑物之中的本地网络。但是这种区别正变的模糊。现在已能通过电话线将LAM网远距离连接，所以它们看起来像一个独立的LAN。

最初，网络用于使终端访问其他电脑，以及在电脑之间传递文件。今天网络能传递电子邮件，访问公共数据库，并开始用于分布式系统。网络还能使某区域的许多用户共享贵重资源，如打印机和磁盘系统。

分布式计算机系统是用协同完成任务的许多网络化计算机建立起来的。在这种环境下，网络中的每一部分都去完成其最擅长的工作。高质量的个人电脑或工作站的图形屏幕提供良好的用户界面。另一方面，大型主机可处理大量的询问并向用户反馈结果。在分布式环境中，用户可以用PC 查询某一中央数据库。PC可将以某特定的语言（如结构化查询语言SQL）写成的询问传递给主机，主机对该询问进行语法分析，并只向用户反馈申请的数据，减少了网络上传输量。如果传输整个文件，PC就必须自己完成查询。

有时，你可能会将许多独立的网络联接起来。这可以用网关和网桥来完成。网关是让某一网络上的用户访问另一类型网络上资源的硬软件组合。例如，网关可用来将个人电脑局域网联接到大型计算机网。网桥是用来联接相似网络的硬软件组合。例如，某公司在其财务和市场部门具有类似而独立的个人电脑局域网，这些网络可用网桥联接。该例中，使用网桥比以

一大型网络形式把所有个人电脑联接起来更为合理，因为独立的部门只是偶然需要访问其他网络的信息。

电脑网络可分为四个主要方面。

第一是数据传输。它解释了在电线中流动的最底层电信号运载信息的原理，并阐明了如何用电信号将数据进行编码的。

第二个方面焦点是数据包传送。它解释了为什么计算机网络使用数据包，并阐明了数据是如何组成数据包进行传送的，上面所讨论的WAN和LAN 网是两种基本网络。

第三个方面覆盖互联网，这是一个重要的思想，使不同的网络技术组成一个大型、严密的通信系统，以及用于全球互联网的TCPIP协议技术。

第四个方面介绍互联网的应用，着重应用中所使用的基础通信网，客户-服务器交互模型，以及应用程序是如何提供电子邮件和网点查询等服务的。

全球因特网的增长是网络化中罪有意思和激动人心的现象之一。10年前，因特网只是涉及几打场所的研究项目。今天，因特网已变成被全世界所有大陆上几乎所有国家数以百万计的人们所使用的生产通信系统。在美国，因特网已联接到大多数企业、学校，以及联邦、州和地方政府的办公室。它将迅速渗透到大多数小学、初高中。而且，许多居民也通过拨号电话联接进人因特网，因特网对社会影响的迹象可从广告、杂志和电视上看到，它常包括提供关于广告人产品和服务信息的因特网网点的参考信息。

一个具有不同网络要求的大型组织需要多种的物理网络。更重要的是，如果该组织针对每个事务选用最佳的网络形式，这组织就会有许多类型的网络。多种网络的主要问题是显然的：联接到某特定网络的计算机只能与联在同一网络的其他计算机进行通信。在20世纪70年代，当大型组织开始形成多种网络时，这问题就变的明显。该组织的各个网络形成一个

孤岛。在许多早期的安装中，各个电脑联到一个独立的网，而使用者不得不选择适宜于各个任务的计算机。也就是说使用者要使用许多显示屏和键盘，并且为了在适当的网络之间传递信息，被迫从一电脑走到另一电脑。他们既不满意又效率低下。因此，大多数现代电脑通信系统允许两台计算机之间的通信，这相似于电话系统所提供的任何两台电话之间的通信方式，被称为全能服务的概念是网络的基本组成部分。通过全能服务，在某组织中任一部门的任一计算机前的使用者都能像任何其他使用者传递信息。而且用户在转变任务时不必转换计算机系统，所有信息都对所有计算机开放。结果，使用者的工作效率变的更高。

用于联网的基本元件是路由器。路由器使一组织能选择适合于某种需要网络技术，并且能用路由器把所有网络联成一单独因特网。

互联网的目的是跨越不同的网络的全能服务。为了在某一因特网中所有电脑之间提供全能服务，路由器必须满足能从网络中取出源信息传送至另一网络的特定目标位置，这任务的复杂性在于基本网络使用的框架形式和寻址方式会是不同的。结果，计算机中需要协议软件，并由路由器形成全能服务。因特网协议克服了框架形式和物理地址不同，从而能在使用不同技术的网络之间进行通信。

总体来说，因特网软件提供了一种单独、严密、有许多计算机的通信系统。这系统能提供全能服务：有一计算机都被赋予一地址，并且任一计算机都能给任一其他计算机传送数据包。更进一步的是因特网协议软件隐藏了物理网络联接，物理地址和路由器信息等细节。这样，使用者或应用程序均不了解基础物理网络或联接这些网络的路由器。

我们说因特网是一虚无网络系统是因为其通信系统是抽象概念。就是说，尽管硬件和软件的组合提供了某种统一的网络环境，但并无这种网络存在。

对互联网的研究已产生奇迹般的结果，互联网以成为现代网络中最重要的概念。事实上，因特网技术已使计算机通信起了革命性的变化。大多数大型组织都已使用互联网作为其首要的计算机通信机构，小组织和个人也开始这样做。更重要的是，TCPIP技术已使全球互联网成为现实，这一网络已联通遍布几乎世界上所有国家的学校、商业组织、政府、军事场所和个人所用的超过一亿台的电脑。