Basic knowledge of computer network

First, the concept of computer network

At the end of this century, human beings are entering the information age, the progress of society and the development of productive forces, to a great extent depends on the human access to information and processing capacity, relying on the progress of information technology.

Information technology contains a wide range of information, including the collection, processing, storage, transmission and distribution, as well as the means to express information. Computer network is the combination of computer and communication technology, is the symbol of information technology progress. In recent years, the Internet, the development of global computer network, has proved the absolute importance of computer network to the information age.

So what exactly is a computer network? How is it structured?

The meanings and understandings of different people to the computer network are not the same. In the early days, people dispersed computers, terminals and their affiliated, using communication media to connect, can achieve mutual communication called network system. In 1970, the computer network was defined as "a collection of computer systems with the ability to share resources (hardware, software, data, etc.), and each with their own functions, at a joint Spring Computing conference held by the American Information Processing Association."

The main difference between the two described above is that the computers of the latter nodes must have separate functions, and the resources (files, data, printers, etc.) must be shared.

With the development of distributed processing technology and from the perspective of user use, the concept of computer networks has also changed, defined as "must have the ability to automatically manage all kinds of resources for users of the operating system, it is scheduled to complete the request of network users, make the entire network resources transparent to users."

To sum up, we will describe the computer network as follows: The computer network is the use of communication lines will be geographically dispersed, with independent functions of many computer systems connected, according to some kind of protocol data communication, to achieve resource sharing information system.

The simplest network is the interconnection of two computers, while the complex computer network connects the world's computers, 1.

Second, the composition of computer network system

Computer network system is composed of communication subnets and resource subnets. The network software system and the network hardware system are the basis of the existence of network system. In the network system, the hardware plays a decisive role in the choice of the network, while the network software is the tool to excavate the potential of the network.

1. Network software

In the network system, every user on the network can enjoy various resources in the system, and the system must control the users. Otherwise, it will cause system confusion, information data destruction and loss. In order to coordinate the system resources, the system needs to manage, dispatch and distribute the network resources through software tools, and take a series of security measures to prevent users from unreasonable access to data and information to prevent the destruction and loss of data and information. Network software is an indispensable software environment to realize network function.

Usually network software includes:

Network protocol and Protocol software: it is a protocol program to implement network protocol functions.

Network communication software: Communication between network workstations is realized through network communication software.

Network operating system: Network operating system is used to achieve system resource sharing, management of user access to different resources of the application, it is the most important network software.

Network management and Network application software: Network management software is used for network resources management and network maintenance software. The network application software is the software which provides the service for the network user and solves the actual problem for the network user.

The most important characteristic of network software is that the focus of network management software is not the function of each individual computer in the network, but how to realize the unique function of network.

2. Network hardware

Network hardware is the material foundation of computer network system. To form a computer network system, the computer and its affiliated hardware devices should be connected with other computer systems in the network first. Different computer network systems, there is a difference in hardware. With the development of computer and network technology, network hardware is becoming more and more diversified, the function is more powerful and more complicated.

(1) Line Controller LC: LC is the interface device of the main computer or terminal device and the modem on the line.

(2) Communication Controller CC (Communication Controller): CC is a device used to control the various stages of data information.

(3) Communication processor CP (Communication Processor): CP is a switch for data exchange, which is responsible for communication processing work.

(4) Front-end processor FEP (Front end Processor): FEP is also the device responsible for communication processing work.

(5) Concentrator C (Concentrator), multiplexer Mux (multiplexor): devices that are connected to multiple remote terminals by means of communication lines.

(6) Host computer.

(7) terminal T (Terminal).

With the development of the computer network technology and the popularization of the network application, the network node equipment will be more and more, the function is more powerful, the design is more complicated.

Third, the classification of computer network

The computer network can be classified according to different standards.

(1) From the network node distribution, can be divided into LAN (local area Network,lan), Wan (Wide area Network,wan) and metropolitan area Network (Metropolitan areas Network,man).

LAN is a small-scale implementation of the computer network, generally in a building, or a factory, a public institution within the unit unique. LAN distance can be within more than 10 km, channel transmission rate of up to 1~20mbps, simple structure, easy wiring. The wide area network can be distributed in one province, one country or several countries. WAN channel transmission rate is low, generally less than 0.1Mbps, the structure is more complex. Metropolitan Area Network is a computer information network set up in a city, providing the information service of the city. At present, many cities in China are building the metropolitan area network.

(2) According to the switching mode can be divided into line switching network (Circurt switching), Message exchange network (message switching) and packet switching network (Packet switching).

Line switching first appeared in the telephone system, the early computer network is used in this way to transmit data, digital signal after transformation into an analog signal before transmission on the line. Message exchange is a digital network. When the communication begins, a message sent by the source is stored in the exchanger, and the switch sends the message according to the destination address of the message, which is called the storage-forwarding method. Packet switching also uses message transmission, but it is not an indefinite length of the message to do the basic unit of transmission, but a long message is divided into a number of fixed-length packet packet, grouped as the basic unit of transmission. This not only greatly simplifies the management of computer memory, but also accelerates the communication speed of information in the network. Because packet switching is superior to line switching and message exchange, it has become the mainstream of computer network.

(3) According to the network topology can be divided into star network, tree-type network, the total Linetype network, ring-type network and mesh network.

Four, the function of computer network computer network since it is to share as the main goal, then it should have the following aspects of the function:

1. Data communication

This function realizes the data transmission between computer and terminal, computer and computer, which is the basic function of network.

2. Resource Sharing

Computers on the network can share resources with each other, including hardware, software, and data. With the advent of the information age, the sharing of resources is of great significance. First, from the investment considerations, users on the network can share the use of online printers, scanners, and so on, saving money. Second, the modern information is more and more large, a single computer has been unable to store it, only distributed on different computers, network users can share these resources. Again, now the computer software in endlessly, in these voluminous software, many are free to share, this is the network of valuable wealth. Anyone connected to the network has the right to use them. Resource sharing provides users with the convenience of using the network.

3. Remote transmission

The development of computer application has been from scientific calculation to data processing, from stand-alone to network. Users in remote locations can transfer data information, communicate with each other and work together.

4. Centralized Management

The development and application of computer network technology has made the modern office means, management and so on changed. At present, there are many MIS system, OA system and so on, through these systems can realize the centralized management of daily work, improve work efficiency, increase economic efficiency.

5. Implement distributed processing

The development of network technology makes distributed computing possible. For large-scale topics, can be divided into a number of small topics, by different computers to complete, and then concentrated, to solve the problem.

6. Load Balancing

Load balancing means that the work is distributed evenly to each computer system on the network. The Network control Center is responsible for distribution and detection, when a computer is overloaded, the system will automatically transfer the load to a lighter computer system to deal with.

Thus, the computer network can greatly expand the function of the computer system, expand its application range, improve reliability, to provide users with convenience, but also reduce costs, improve performance and price ratio.

Basic knowledge of computer network