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This article introduces the relevant knowledge of "what are the basic knowledge of computer network". In the operation of actual cases, many people will encounter such a dilemma. Next, let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

1. Know the Internet

The network connects the hosts, while the Internet connects many different networks, so the Internet is the network of the network. ISP, an Internet service provider, can obtain many IP addresses from Internet management agencies, and has communication lines, routers and other networking equipment. Individuals or institutions can access the Internet by paying a certain fee to ISP. At present, the Internet is a multi-level ISP structure. According to the size of the coverage area, the ISP is divided into the first layer ISP, regional ISP and access ISP. The Internet exchange point IXP allows two ISP to connect directly without going through a third ISP.

2. Computer network architecture

(1) five-layer protocol

A. application layer: provides data transfer services for specific applications, such as HTTP, DNS, etc. The data unit is the message.

B. transport layer: provides general data transfer services for processes. As there are many application layer protocols, defining a general transport layer protocol can support an increasing number of application layer protocols. The transport layer includes two protocols: transmission control protocol TCP, which provides connection-oriented and reliable data transmission services, and user Datagram protocol UDP, which provides connectionless and best-effort data transmission services, and the data unit is user Datagram. TCP mainly provides integrity services, while UDP mainly provides timely services.

C. network layer: provides data transmission services for hosts. The transport layer protocol provides data transmission services for processes in the host. The network layer encapsulates the message segments or user datagrams delivered by the transport layer into packets.

D. data link layer: the network layer is aimed at the data transmission service between hosts, and there can be many links between hosts, and the link layer protocol provides data transmission services for hosts on the same link. The data link layer encapsulates the packets passed down from the network layer into frames.

E. physical layer: consider how to transmit data bit streams on the transmission media, rather than referring to the specific transmission media. The role of the physical layer is to shield the differences in transmission media and means of communication as much as possible, so that the data link layer does not feel these differences.

(2) OSI

The purpose of the presentation layer is data compression, encryption, and data description, which obviates the need for applications to worry about different internal formats of data on each host. The purpose of the session layer is to establish and manage sessions. The five-layer protocol does not have the presentation layer and session layer, but leaves these functions to application developers.

(3) TCP/IP

It has only four layers, which is equivalent to merging the data link layer and the physical layer into the network interface layer in the five-layer protocol. The TCP/IP architecture does not strictly follow the concept of OSI layering, and the application layer may directly use the IP layer or the network interface layer. TCP/IP protocol family is an hourglass shape, small in the middle and big on both sides, in which IP protocol plays an important role.

(4) the process of data transmission

In the downward process, the header or tail required by the lower layer protocol needs to be added, and the header and tail are constantly detached in the upward process. The router has only the following three layers of protocols, because the router is in the core of the network and does not need to provide services to processes or applications, so there is no need for the transport layer and the application layer.

3. Network application architecture

At present, there are two mainstream architectures: client-server architecture and peer-to-peer architecture. The comparison between the two architectures is as follows:

(1) continuity: if the server fails, the whole system will be paralyzed, but P2P will not.

(2) Security: in Camp S mode, security is higher because it only needs to ensure the security of the server. In P2P mode, it is very difficult to ensure the security of every node.

(3) the maintainability of resources: in the Cramp S mode, shared resources are centrally stored on the server, the search and update of resources are relatively simple, the backup and recovery of data are also easy to achieve, and the maintainability of resources is better. In P2P mode, shared resources are stored on any client in the system, the search and update of resources are more complex, data backup is more difficult, and the maintainability is poor.

(4) Network communication performance: in Cpact S mode, network communication is mainly concentrated between the client and the server, and there is generally no direct interaction between the client and the client. In P2P mode, there is frequent data communication between clients and other clients, and P2P mode needs to occupy more network bandwidth.

(5) Extensibility: in Cpact S mode, the performance of the server will gradually decline with the increase of the client or workstation. In order to ensure the effective operation and timely response ability of the server, it is necessary to restrict the growth of the number of clients or workstations, which weakens the scalability of the system to a certain extent. In P2P mode, the growth of nodes may improve the performance of the system.

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