中英对照：计算机网络与数据通信

浅谈计算机网络与数据通信

摘要：人类社会已进入信息化时代。随着计算机技术、通信技术和信息处理技

术的发展，计算机从单机进入了广域网和局域网的计算机网络化时代。作为一种信息交换手段的计算机网络通信在人们的日常生活和社会生活中正起着越来越重要的作用。

本论文从计算机与通信相结合的两方面入手，介绍了计算机网络通信的产生与发展，以及对人类社会及数据通信的发展产生的深远影响。详细阐述了计算机网络、网络结构、网络分类、网络协议；数据通信的产生、构成原理、交换方式、分类以及计算机网络通信在各方面的应用。

展望未来，计算机网络和数据通信有着不可估量的发展空间，它们必将向着数字化、综合化、宽带化方向发展，计算机网络通信将向着综合业务数字方向发展。数据、语音、图像等各种数据通信将在各个层次、各个领域得到综合利用。信息高速公路的建成，必将为我们的生活提供更加高效、优质、快捷、便利的服务。

概述：自世界上第一台数字电子计算机1946年问世后，在最初10年内，计算

机和通信没有什么关系。当时计算机以“计算中心”的服务模式工作。直至1954年，一种收发器（transceiver）的终端制造出来后，人们才首次使用这种终端通过电话线路将数据发送到远方的计算机。此后，计算机开始与通信结合，计算中心的服务模式逐渐让位于计算机网络的服务模式。计算机与通信相结合主要有两方面：一方面，通信网络为计算机之间的数据传输和交换提供了必要的手段；另一方面，计算机技术的发展渗透到通信技术，又提高了通信网络的性能。（如：程控交换机）实践表明，计算机网络的产生与发展，对人类社会及数据通信的发展产生了深远的影响。

一．计算机网络的发展

1.1面向终端的计算机通信网

用一台计算机专门进行数据处理，用一台通信处理机或前端处理机（front-end processor，FEP）（早期为线路控制器）通过调制解调器与远程终端相连。通信处理机完成全部通信任务，包括串行和并行传输的转换，因为在通信线路上是串行传输，而在计算机内部是并行传输，让计算机专门进行数据处理。调制解调器将终端或计算机的数字信号变成可以在电话线上传输的模拟信号或完全相反的变换。由于前端机可以采用比较便宜的小型计算机，所以自20世纪60年代初起一直被广泛使用。这种联机系统称为面向终端的计算机通信网。也有人将这种最简单的计算机网络称为第一代计算机网。这种网络本质上是以单个主机为中心的星状网，各终端通过通信线路共享主机的软件和硬件资源。

2.2分组交换网

分组交换（packet switching）也称为包交换，它是现代计算机网的技术基

础。但是，这一技术经历了一个发展过程。

在有线电话出现不久，人们就认识到在所有用户之间架设直达的线路，不仅线路投资太大，而且没有必要，可以采用交换机实现用户之间的互联。一百多年来，尽管电话交换机从人工转接发展到现代的程控交换机，经过多次更新换代，但交换方式始终未变，都是采用电路交换（circuit switching）,即通过交换机实现线路的转接，在两个要求通话的用户之间建立一条专用的通信线路，用户在通话之前，先要申请拨号，待建立一条从发端到收端的物理通路后，双方才能互相通话。在通话的全部时间里，用户始终占用端到端的固定线路，直到通话结束，挂起电话（释放线路）为止，这种通信系统不适合传送计算机或终端的数据。因此，必须寻找适合于计算机通信的交换技术，才能使计算机网络得到发展。

存储转发分组交换技术，实质上采用的策略是断续（或动态）分配传输通道。因此，非常适合传输突发式的计算机数据，极大地提高了通信线路的利用率，降低了用户的使用费用。用户不仅共享通信子网的资源，还可共享资源子网的硬件和软件资源。这种以通信子网为中心的计算机网络称为第二代计算机网络，它的功能比第一代计算机网络扩大很多。今天著名的全球性网络因特网（Internet）就是在此基础上形成的。我国公用分组交换网（简称CNPAC）于1989年11月建成。

1.3因特网时代

从20世纪80年代末期以来，因特网（Internet）飞速发展，使因特网成为世界上最大的国际性计算机互联网。从20世纪90年代开始，世界进入因特网时代。为了适应用户数量迅猛增长的需要，提高服务质量，在今后建造新一代因特网的设想并开发下一带网络结构，实现以下主要目标：

（1）大大提高网络的传输速率，其端到端的传输速率要超过100Mbps至10Gbps。（2）采用高速全光缆网络，实现更快速的交换和路由选择，同时具有为实时应用保留带宽的能力。

（3）在整个因特网的管理和信息可靠性、安全性方面要有很大的改进。

（4）使用更加先进的网络服务技术，开发许多带有变更性的应用，如高性能全球通信、远程医疗、远程教学等。

二．计算机网络及其协议

2．１计算机网络

计算机网络（Computer Network）,就是通过光缆、双绞电话线或有、无线信道将分散在不同地点并具有独立功能的多台计算机系统互相连接，按照网络协议进行数据通信，通过网络各用户可实现网络资源共享的信息系统。如：文档、程序、打印机等。

计算机网络按地理位置划分，可分为网际网、广域网、城域网、和局域网四种。Internet是世界上最大的网际网，局域网是目前使用最多的计算机网络。如：利用局域网我公司人力部门进行人力资源、档案管理，财务部门进行财务帐目管理，材料部门进行日常材料管理，党群部门进行政治思想宣传教育管理，技术部门进行技术支持等。这样一来大大地提高了日常管理，节省了开支，提高了我公司综合管理能力。

2．2计算机网络结构

一般来讲，计算机网络由计算机系统、通信链路（指线路及其设备）和网络结点组成。从功能上，可以将计算机网络分为资源子网和通信子网两部分。

资源子网中主要包括拥有资源的用户主机和请求资源的用户终端、通信子网接口设备和软件等，提供访问网络和处理数据的能力。

通信子网提供网络通信功能，完成主机之间的数据传输、交换、控制和变换等通信任务。通信子网可分为交换和传输两部分，交换部分指结点交换机，结点交换机通常是一台小型计算机，起通信控制与转发作用；传输部分指高速通信线路，负责传输信息。

如果把网络单元定义为结点，两个结点间的连线称为链路，则从拓扑学的观点看，计算机网络就是由一组结点组成，网络结点和链路的几何图形就是网络拓扑结构，或网络结构。网络中的结点有两类：端结点和转接结点。端结点指通信的源和宿结点，也叫做访问结点，例如，用户主机和用户终端。转接结点指网络通信过程中起控制和转发信息作用的结点，例如，程控交换机、通信处理机、集线器和终端控制器等。通信子网的拓扑结构有很多种，主要有星状、树状、总线状、环状和网状等几种拓朴结构。

三．结束语

展望未来，随着计算机网络技术、通信技术和信息处理技术的不断发展，计算机网络和数据通信有着不可估量的发展空间。它们必将向着数字化、综合化、宽带化方向发展，计算机网络通信将向着综合业务数字方向发展。数据、语音、图像等各种数据通信将在各个层次、各个领域得到综合利用。如：3G业务、光缆入户以及铁路系统采用的GSM-R系统等。信息高速公路的建成，必将为我们的生活提供更加高效、优质、快捷、便利的服务。

Computer Networks and Data Communication

Abstract:Human society has entered the information age. With computer technology, communication technology and information processing technology, from a single computer into the WAN and LAN computer network era. Information exchange as a means of computer network communication in people's daily life and social life are playing an increasingly important role.

This paper from the computer and communications aspects of combining the two, introduced the production of computer network communication and development, and data communications on human society and the development of far-reaching implications. Elaborated on the computer network, network structure, network classification, network protocol; data communication generation, composition theory, exchange, classification and communication in all aspects of computer network applications.Looking to the future, computer networks and data communications immeasurable space for development, they will surely toward digital, integrated, broadband direction, computer network communications will be toward integrated services digital direction. Data, voice, images and other data communications in all levels and utilization in various fields. The completion of the information highway, will provide for our lives more efficient, high quality, efficient and convenient service.

Overview:Since the world's first digital electronic computer in 1946 after the advent of the first 10 years, nothing to do with computers and communications. At that time the computer to "Computing Center" service mode. Until 1954, a transceiver (transceiver) of the terminal manufacturers came out, it is only the first time using this terminal through the telephone line to send data to remote computer. Since then, computer and communications begin with, computer center service model gradually give way to the computer network service model. The combination of computer and communication are two aspects: on the one hand, communication networks, data transmission between the computer and provide the necessary means of exchange; other hand, the penetration of computer technology to communications technology, but also improves the performance of communications networks . (Eg: PBX) proved that the emergence and development of computer networks, data communication on human development of society and had a profound impact.

I. Development of computer networks

1.1 for the terminal computer communication networks

Devoted to the use of a computer data processing, communications processor or

with a single front-end processor (front-end processor, FEP) (early for the line controller) and remote terminal connected via modem. Communication processor to complete all communication tasks, including serial and parallel transmission conversion, because the communication is a serial transmission line, but inside the computer is the parallel transport, let the computer dedicated to data processing. Terminal or computer modem into a digital signal can transmit analog telephone line signal or the opposite transformation. Front-end machine can be used as less expensive small computer, so the 60 years since the beginning of the 20th century, has been widely used. This online system, known as a computer communications network for the terminal. It was also the most simple computer network such as the first generation of computer network. This network is essentially based on a single host as the center of the star network, the terminal communication line shared by the host software and hardware resources.

2.2 Packet Switched Network

Packet switching (packet switching), also known as packet switching, which is the technical basis of modern computer networks. However, this technology has undergone a process of development.

Appear soon in the wireline telephone, it is recognized that all users set up direct lines, not only investment in large lines, but not necessary, the switch can be used to achieve the interconnection between users. Hundred years, despite calls from manual transfer switch to the modern program-controlled switches, after several replacement, but the exchange remained unchanged, and are based on circuit-switched (circuit switching), achieved through the line transfer switch the two requirements calls between users of a dedicated communication line, the user calls, have to apply for dial-up, to be established from the beginning to the receiving end of a physical channel, the two sides can talk to each other. All the time in the call, the user always takes the fixed-line end to end until the end of the call, hang up call (release circuit), the communication system is not suitable for such a computer or terminal to send data. Therefore, we must look for the exchange of computer communications technology, to make computer networks to develop.

Store and forward packet switching technology, in essence, the strategy is to use intermittent (or dynamic) allocation of transmission channel. Therefore, it is suitable for computer data transmission burst, which greatly improves the utilization of communication lines, reducing the use of user fees. Users to not only share the resources of the communication subnet, subnet can share the resources of hardware and software resources. This kind of communication subnet as the center of the computer network known as the second-generation computer network, which features than many first-generation computer networks expand. Now known as the global network the Internet (Internet) is formed on this basis. China Public Packet Switched Network (referred to as CNPAC) completed in November 1989.

1.3 Internet age

From the 20th century, since the late 80s, the Internet (Internet) the rapid

development of the Internet to become the world's largest international computer Internet. 90s from the 20th century, the world access to the Internet era. In order to meet the needs of rapid growth in the number of users, improve service quality, in the future the idea of building a new generation of the Internet and the development of the area under the network structure, to achieve the following main objectives: (1) significantly improve the network transmission rate, the end of the transmission rate to more than 100Mbps to 10Gbps.

(2) using high-speed all optical network, to achieve faster switching and routing, both the bandwidth reserved for the ability of real-time applications.

(3) management and information throughout the Internet reliability, security aspects have a lot of improvement.

(4) the use of more advanced Web services technology to develop with the changing nature of many applications such as high-performance global communications, telemedicine, distance learning and so on.

II. Computer Network and Protocol

2.1 Computer Network

Computer Networks (Computer Network), is through the fiber optic cable, twisted pair telephone lines or so, radio channel will be scattered in different locations and have multiple independent functions interconnected computer systems, according to network protocol data communication can be achieved through the network the user sharing of network resources information system. Such as: documents, programs, printers and so on.

Computer Network by geographical location, can be divided into Internet, WAN, MAN, and LAN four. Internet is the world's largest Internet network, LAN is the most widely used computer network. Such as: the use of our manpower department local area network of human resources, records management, financial sector financial account management, materials management departments everyday materials, party-political and ideological propaganda and education departments of management, technical department for technical support. As a result greatly improve the daily management, save costs and increase the capacity of integrated management of the company.

2.2 The structure of computer networks

In general, the computer network by a computer system, communication links (refer to lines and equipment) and the network node points. From the functions, resources can be divided into subnets computer networks and communication subnet in two parts.

Resource subnet includes have the resources and request resources for the user host user terminal, the communication subnet interface devices and software to provide access to the network and processing data.

Communications provides network communications subnet, complete data transfer between the host, exchange, control and transform communication task. Communications switching and transmission subnet can be divided into two parts,

the exchange part of that node switch, the switch node is usually a small computer, play the role of communication control and forwarding; transmission part refers to the high-speed communication lines, responsible for the transmission of information. If the unit is defined as the network nodes, the connection between two nodes as links from the topology point of view, the computer network is composed by a set of nodes, network nodes and links of the geometry is network topology, or network structure. Nodes in the network there are two types: end nodes and transit nodes. End node refers to the traffic's source and destination nodes, also called access nodes, for example, the user host and user terminals. Node refers to the network adapter in the communication process from the role of information control and forwarding nodes, such as program-controlled switches, communications processor, hub and terminal controllers. Communication subnet topology there are many, the main star, tree, bus-like, ring and meshed topology of several.

III. Conclusion

Looking ahead, with computer network technology, communications and information processing technology continues to evolve, computer networks and data communications immeasurable development. They will toward digital, integrated, broadband direction, computer network communications will be toward integrated services digital direction. Data, voice, images and other data communications in all levels and utilization in various fields. Such as: 3G services, cable home and the railway system of the GSM-R system. The completion of the information highway, will provide for our lives more efficient, high quality, efficient and convenient service.