Data Communication Computer Network 简明教程

Computer Network Overview

What is a Computer Network?

计算机网络是指出于在各种用户之间共享信息和资源的目的而相互连接的计算设备的集合。

A computer network is a collection of computing devices that are connected with each other for the purpose of information and resource sharing among a wide variety of users.

将计算机与打印机等计算机化外围设备互连的系统称为计算机网络。计算机间的这种互连促进了它们之间的信息共享。计算机可以通过有线或无线媒体互相连接。

A system of interconnected computers and computerized peripherals such as printers is called computer network. This interconnection among computers facilitates information sharing among them. Computers may connect to each other by either wired or wireless media.

Features of Computer Network

计算机网络的特点如下 −

The features of a computer network are −

  1. Sharing − Computer networks enable sharing of files, software, hardware resources and computing capabilities.

  2. Speed: The communication speed among the components is fast enough to be comparable with a centralized system.

  3. Scalability − Sizes of computer networks dynamically increase with time. The networks have to be scalable so that they can evolve adequately for future deployments.

  4. Integration − All the components of the network work in a coordinated manner for a seamless user experience.

  5. Security − Networks allow security and access rights to the users for restricted sharing of resources and information.

  6. Cost Effectiveness − Networking reduces the deployment cost of hardware and software of a centralized system.

Classification of Computer Networks

计算机网络基于各种因素进行分类，包括：

Computer networks are classified based on various factors.They includes:

  1. Geographical span

  2. Inter-connectivity

  3. Administration

  4. Architecture

Geographical Span

从地理位置来看，网络可以归入以下类别之一：

Geographically a network can be seen in one of the following categories:

  1. It may be spanned across your table, among Bluetooth enabled devices,. Ranging not more than few meters.

  2. It may be spanned across a whole building, including intermediate devices to connect all floors.

  3. It may be spanned across a whole city.

  4. It may be spanned across multiple cities or provinces.

  5. It may be one network covering whole world.

Inter-Connectivity

网络的组件可以通过不同的方式相互连接。连通性是指逻辑上、物理上或两者兼而有之的连接。

Components of a network can be connected to each other differently in some fashion. By connectedness we mean either logically , physically , or both ways.

  1. Every single device can be connected to every other device on network, making the network mesh.

  2. All devices can be connected to a single medium but geographically disconnected, created bus like structure.

  3. Each device is connected to its left and right peers only, creating linear structure.

  4. All devices connected together with a single device, creating star like structure.

  5. All devices connected arbitrarily using all previous ways to connect each other, resulting in a hybrid structure.

Administration

从管理员的角度来看，网络可以是属于单个自治系统的私有网络，并且无法在其物理或逻辑域外部进行访问。网络可以是所有人都可以访问的公共网络。

From an administrator’s point of view, a network can be private network which belongs a single autonomous system and cannot be accessed outside its physical or logical domain.A network can be public which is accessed by all.

Network Architecture

  1. There can be one or more systems acting as Server. Other being Client, requests the Server to serve requests.Server takes and processes request on behalf of Clients.

  2. Two systems can be connected Point-to-Point, or in back-to-back fashion. They both reside at the same level and called peers.

  3. There can be hybrid network which involves network architecture of both the above types.

Network Applications

计算机系统和外围设备连接起来形成网络。它们提供了许多优点：

Computer systems and peripherals are connected to form a network.They provide numerous advantages:

  1. Resource sharing such as printers and storage devices

  2. Exchange of information by means of e-Mails and FTP

  3. Information sharing by using Web or Internet

  4. Interaction with other users using dynamic web pages

  5. IP phones

  6. Video conferences

  7. Parallel computing

  8. Instant messaging