Development of computer network
Source: Shangpin China |
Type: website encyclopedia |
Date: August 24, 2012
Beijing website construction The company advocates products in China: the birth of the first electronic computer ENIAC in 1946 announced that human beings had entered the information society. Computer network was born in the mid-1950s, which is the combination of modern computer technology and communication technology. Especially in the past 20 years, the computer network has developed rapidly. With the emergence of the Internet, network and communication technology have gradually become an important factor affecting the economy, science and culture of a country and region.
Development of computer network
The development of computer network has gone through a process of evolution from simple to complex, from low level to high level. From the online system formed to solve the collection and processing of remote computing information, it has developed to the computer cluster interconnected for the purpose of resource sharing. The development of computer network has promoted the development of computer technology and communication technology, making it penetrate into all fields of social life. So far, its development process can be roughly divided into four stages.
1. Terminal oriented computer network
When the world's first electronic computer ENIAC was born in the United States in 1946, there was no direct connection between computer technology and communication technology. In the early 1950s, for its own security, the United States established a semi-automatic ground air defense system (SAGE) in the northern part of the United States mainland and in Canada, and tried to combine computer technology with communication technology.
This online system centered on a single computer is called terminal oriented remote online system. This system is the embryonic form of computer network formed by the combination of computer technology and communication technology, so it is also called terminal oriented computer communication network. In the early 1960s, the American airline booking system SABRE-1 was a typical application of this kind of computer communication network. The system was composed of a central computer and more than 2000 terminals distributed throughout the United States. Each terminal was connected to the central computer through telephone lines.
The stand-alone system mainly has the following two disadvantages:
① The host is not only responsible for data processing, but also for managing communication with the terminal, so the host is overburdened.
② Because one terminal uses one communication line alone, the utilization rate of communication line is low. In addition, every time a terminal is added, the software and hardware of the line controller need to be greatly changed.
In order to reduce the burden of the host, a front-end processing device front-end processor (FEP) can be set between the communication line and the computer. The FEP is specially responsible for the communication control with the terminal, and the host is allowed to process data. In order to improve communication efficiency and reduce communication costs, a concentrator is added where remote terminals are concentrated. The concentrator is used to centralize several terminals through low-speed communication lines and connect them to high-speed lines. Then it is connected to the front-end processor through high-speed lines, and the front-end processor and concentrator are undertaken by a minicomputer.
2. Computer communication network
This kind of computer network interconnected by multiple autonomous hosts through communication lines is usually divided into resource subnet and communication subnet, as shown in Figure 5-3.
The resource subnet consists of all hosts, terminals, terminal controllers, peripherals (such as network printers, disk arrays, etc.) and various software resources in the network. It is responsible for data processing of the whole network and providing network resources and services to network user workstations or terminals. The communication subnet is composed of various communication equipment and lines, and is responsible for data transmission, transfer, transformation and other communication processing work of the resource subnet.
Network users' access to the network can be divided into two categories.
① Local access: access to the local host does not go through the communication subnet, but only within the resource subnet.
② Network access: Access the resources on the remote host through the communication subnet.
3. Standard protocol computer network
The third stage of computer network development is the formation of network architecture and the internationalization and standardization of network protocols. In the late 1970s, the International Organization for Standardization (ISO) and the Information Processing Standardization Technical Committee established a special organization to study and formulate network communication standards to achieve international standardization of network architecture. 1984 ISO has officially issued an international standard ISO7498 called "Open System Interconnection Reference Model", which is called OSI/RM (Open System, Interconnection/Reference Model) for short, that is, the famous OSI 7-tier model. The development and perfection of OSI/RM and standard protocols have greatly accelerated the development of computer networks. Many large computer manufacturers have announced their support for the OSI standard, and actively research and develop products that meet the OSI standard.
The computer network following the international standardization protocol has a unified network architecture. Manufacturers need to develop their own network products according to the internationally recognized standards, so as to ensure that products of different manufacturers can communicate in the same network. This is the meaning of "open".
At present, there are two dominant network architectures: one is OSI/RM proposed by the International Organization for Standardization, and the other is the de facto industrial standard TCP/IPRM (TCP/IP reference model) used by the Internet.
4. High speed intelligent computer network
Since the late 1980s, computer network technology has entered a new stage of high-speed intelligent development. The characteristics of computer network development at this stage are: interconnection, high-speed, intelligence and wider application. The development of high-speed network technology is reflected in the broadband integrated services data network B-ISDN, frame relay, asynchronous transfer mode ATM, high-speed LAN, switched LAN and virtual network.
With the increase of network scale and network service functions, countries are carrying out research on Intelligent Network. IN. The concept of intelligent network was put forward by the United States in 1984. The definition of intelligent network does not have the meaning of "intelligence" commonly understood by people. It is just a "service network". The purpose is to improve the ability of communication network to develop services. Its emergence has attracted the attention of telecommunications departments around the world. ITU began to list it as a research topic in 1988. In 1992, ITU formally defined the intelligent network and formulated a system that can generate and realize various new services quickly, conveniently, flexibly, economically and effectively. The goal of this system is to apply to all communication networks, that is, not only to the existing telephone network, N-ISDN network and packet network, but also to mobile communication network and B-ISDN network. As time goes by, the application of intelligent network will develop to a higher level. This article was published in UEO Marketing website construction Company Shangpin China //ihucc.com/
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