Shulou(Shulou.com)06/03 Report--

I. Computer networks

Concept: A computer network is a collection of more than two computers interconnected by cable, telephone line, or wireless communication

Component elements: Network nodes: End nodes: Source and sink nodes

Forwarding node: refers to the network communication process control and forwarding information node

A channel over which information is transmitted.

II. Main functions

1. resource sharing

2. network communication

3. Distribution processing

4. centralized management

5. balanced load

III. Characteristics

1. reliability

2. efficiency

3. independence

4. extensibility

5. cheapness

6. Distribution

7. ease of operation

IV. Structure and composition of computer network

- Network hardware: generally refers to the network of computers, transmission media and network connection equipment, etc.

- Network software: generally refers to network operating system, network communication protocol, etc.

Note: Network hardware: host computer, network workstation, network terminal, communication processor, communication line, information conversion equipment

Network software: network operating system, network protocol software, network management software, network communication software, network application software

Computer topology: all computers on the network are connected to each other by a cable

bus structure

annular structure

star structure

tree structure

bus structure

1. Features: No need to plug in any other connecting devices

2. Advantages: Simple connection, easy installation, low cost

Disadvantages: Slow data transfer, difficult maintenance

annular structure

1. Features: Each node user is connected to two adjacent node users.

2. Benefits: Short cable length: Ring topology networks require cable lengths similar to bus topology networks, but much shorter than star topology networks

Disadvantages: When there are too many nodes, it affects the transmission efficiency. A break in a ring will cause the failure of the whole system, and the process of node joining and withdrawing is complex.

Fault detection is difficult: because it is not centralized control, fault detection needs to be carried out at each node of the network, and fault detection is not easy.

star structure

1. Features: Each node is connected to the central node by a separate communication line.

2. Advantages: Simple structure, easy maintenance and management, because when a computer or headline cable has a problem, it will not affect the normal communication of other computers, and maintenance is easier.

Disadvantages: dedicated communication lines, high cable cost; central node is the reliable bottleneck of the whole network, failure of the central node will lead to network paralysis

tree structure

1. Features: Tree structure is an extension of star structure, which consists of root nodes and branch nodes.

2. Advantages: Simple structure and low cost. Expansion nodes are convenient and flexible.

Disadvantages: the dependence on the root node is large, once the root node fails, the whole network will not work; the cable cost is high.

VI. Classification of computer networks

local area network (LAN)

Metropolitan Area Network (MAN)

Wide Area Network (WAN)

VII. Mode of dissemination

1. broadcast network

Unicast: One-to-one transmission is used to send data to all destination nodes in the network.

Multicast: The use of one-to-one form of transmission, data sent to a group of hosts in the network. Broadcast: A one-to-all transmission format that sends data to all destination nodes in the network. Point-to-point network Point-to-point propagation mode is mainly applied to WAN, and the topology structures usually adopted are star type, ring type, tree type and mesh type.

VIII. Classification of transmission media

1. Wired Network

Twisted pair: It is characterized by economy, convenient installation, general transmission rate and anti-interference ability, widely used in local area network. (2) coaxial cable: commonly known as thin cable, now gradually eliminated. Fiber optic cable: characterized by long fiber transmission distance, high transmission efficiency and strong anti-interference, it is an ideal choice for high security networks. 2. Wireless Network (1) Wireless telephone network: It is a promising way to connect. Voice broadcasting network: low price, easy to use, but poor security. (3) Wireless TV network: high penetration rate, but unable to interact with users in real time on a channel. (4) Microwave communication network: communication confidentiality and security are better. (5) Satellite communication network: capable of long-distance communication, but expensive

IX. Classification of transmission technologies

General telecommunication network: general telephone network, integrated digital telephone network, integrated services digital network.

Digital data network: A digital transmission network that uses permanent or semi-permanent circuits provided by digital channels to transmit data signals. Virtual Private Network: refers to a virtual network formed by customers based on the intelligent characteristics of DDN and utilizing part of the network resources of DDN. Microwave spread spectrum communication network: It is a method for TV transmission and enterprises to set up intranet and access Internet, which is very important in mobile communication. Satellite communication network: It is an air communication network developed in recent years. Compared with terrestrial communication networks, satellite communication networks have many unique advantages.

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