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Definition of computer network
Computer networks, with 通信线路and 通信设备distributed in a computer system having a plurality of individual functions in different locations connected to each other, in 网络软件the support of each other to realize the 数据通信和资源共享system.
Another description:
A system that physically interconnects multiple computers, terminals and their ancillary equipment with independent functions distributed in different geographic locations, communicates with each other according to network protocols, and aims to share hardware, software, and data resources is called a computer network.
Division of Computer Network
Divided into communication subnet and resource subnet
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Communication subnet provides information transmission
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Resource subnet provides shared resources
Classified according to network coverage
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LAN (Local Area Network)
- Coverage range is small (can be several hundred meters to several kilometers)
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WAN (Wide Area Network)
- Wide coverage (generally between countries or regions)
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MAN (Metropolitan Area Network)
- Network radius is between LAN and WAN
The development of computer networks
The development of computer networks is divided into the following four stages:
- Remote terminal connection phase
- Computer network stage
- Computer network interconnection stage
- Information superhighway
In the remote terminal online phase, at first, a host is connected to several terminals, and then the communication control machine CCP is introduced, and the CCP is responsible for the communication between the host and the terminal. During this period, the representative system was the airline ticket booking system used by the United States in 1963.
In the computer network stage, at first several hosts were directly connected, and then CCPs were connected to each other to be responsible for the direct communication of the machines. During this period, the representative system was ARPANET. ARPANET is the predecessor of the Internet today. ARPA, the Advanced Research Projects Agency established by the U.S. Department of Defense, has led many projects, such as drones and aerospace aircraft.
In the stage of computer network interconnection, it is necessary to solve the problem of the chaotic network system in the previous stage. In the computer network stage, without a unified industry standard, it is difficult to cooperate with the equipment produced by various enterprises. In 1984, the International Organization for Standardization announced the Open System Interconnection Model (OSI), pointing out that by installing OSI standards, products of different companies can be used together.
In the information superhighway stage, the information superhighway was first proposed by the United States. In September 1993, the US government announced the implementation of a new high-tech plan: referred to as NII "National Information Infrastructure". my country's information foundation is still weak, and it is in the construction stage of the information highway.