Network protocol model

1、 data
Data generation
In the field of computer , Data is the carrier of all kinds of information .

Data transmission

The data generated by most applications needs to be transferred between different devices .

2、 Network reference model and standard protocol
1)OSI Reference model
7. application layer

Provide interfaces to applications .

6. The presentation layer

Data format conversion , To ensure that the application layer data generated by one system can be recognized and understood by the application layer of another system .

5. The session layer

Establish... Between the two sides of the communication 、 Manage and terminate sessions .

4. Transport layer

establish 、 The process of transferring and canceling data from one end to the other . Control the speed of transmission rhythm , Adjust the sorting of data, etc .

3. The network layer

Define logical address ; Realize the forwarding of data from source to destination .

2. Data link layer

Encapsulating packet data into frames ; Realize the point-to-point of data on the data link 、 Or point to multipoint direct communication ; Error detection .

1. The physical layer

Upload and output bitstream on media ; Provide mechanical and electrical protocols .

2)TCP/IP Reference model

3)TCP/IP Common agreements

4) Common protocol standardization organizations
IETF(Internet Engineering Task Force)- Internet engineer task force
a) Responsible for developing and promoting Internet protocols （ In particular, it constitutes TCP/IP Protocol of protocol family ） A voluntary organization , adopt RFC Release new or replace old protocol standards .

IEEE(Institute of Electrical and Electronics Engineers)- Institute of electrical and Electronics Engineers

b)IEEE Developed the world's electronic policy 、 Electrical and computer science 30% The standard of left and right , Well known are IEEE802.3(Ethernet)、IEEE802.11(Wi-Fi) etc. .

ISO(International Organization for Standardization)- International Organization for Standardization

c) In formulating computer network standards ,ISO It is an international organization that plays an important role , Such as OSI Model , Defined in ISO/IEC 7498-1.

5) application layer
The application layer provides an interface for the application software , Enable applications to use network services . The application layer protocol specifies to use the corresponding transport layer protocol , And the ports used by the transport layer .
The application layer of the PDU go by the name of Data（ data ）.

FTP（File Transfer Protocol） Is a protocol used to transfer files from one host to another , For files “ download ” and “ Upload ”, It uses C/S（Client/Server） structure .

Telnet It is a standard protocol for providing remote login service in data network . Telnet It provides users with the ability to complete the work of remote devices on the local computer .

HTTP（HyperText Transfer Protocol） It is the most widely used network protocol on the Internet . Design HTTP The original purpose is to provide a release and reception HTML Page method .
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