What is the OSI model
OSI model rules
The functions of each layer of the OSI model
1.Physical layer
Define the transmission mode, define the transmission rate, bit synchronization, bit encoding, etc.
2. Data link layer
The information you want to send is composed into a data packet, called a "frame". Each frame is divided into two parts: Header + Data. The header contains some description items of the data packet, such as the Mac address of the sender and receiver, data type, etc.
3. Network layer
IP addressing and routing. In a network environment, two devices may pass through many data links and may also pass through many communication subnets. The main function of the network layer is to select an appropriate path for communication. It will add headers containing information based on the previous layer of data: IP address, version, length and other information.
4. Transport layer
Establish and manage port-to-port communication. It will add a header based on the data of the previous layer, including information: port information of the sender and receiver, protocol information, etc.
5. Application layer
To provide services for applications, we can decide which protocol to use to process data and transmit it based on the information we want to convey. It adds headers to the original data, containing information: protocol information, etc.
6. Presentation layer
Data format conversion, code conversion, and data encryption. In order to have unified rules between different devices, the presentation layer will convert the data into a format that is compatible with each system format and suitable for transmission. The presentation layer is like a translator, translating data-related information into internationally accepted rules.
7. Session layer
Establish, manage and maintain sessions
