Explain the seven-layer structure of the ISO/OSI protocol model. What are the main functions of each layer?
The ISO/OSI 7-layer reference model includes: physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer.
The physical layer mainly deals with the mechanical, electrical and process interfaces, as well as the physical transmission medium under the physical layer.
The main task of the data link layer is to strengthen the function of the physical layer to transmit the original bits and make it appear as an error-free line to the network layer.
The network layer is related to the operation control of the subnet. One of the key issues is to determine how the packet is routed from the source to the destination.
The basic function of the transport layer is to receive data from the session layer, and divide it into smaller units when necessary, and pass it to the network layer, and ensure that the pieces of information arriving at the other party are correct.
The session layer allows users on different machines to establish session relationships.
The presentation layer performs certain specific functions, such as encoding data with a standard method that everyone agrees on.
The application layer contains a large number of protocols that people generally need.
