A quick understanding of the seven-layer reference model of computer network OSI

In 1984, the International Organization for Standardization (ISO) issued the Open Systems Interconnection reference Model (OSI). The OSI reference model divides the network into seven layers, including physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer. Physical layer

The physical layer mainly completes the transmission of the original bit stream between adjacent nodes. The main equipment of the physical layer is, network cable, repeater. Data link layer

The upper layer data is encapsulated into a fixed format frame. The data frame encapsulates the source physical address (source MAC address) and destination physical address (destination MAC address), as well as verification information to ensure the accuracy of the information. The main devices in the data link layer are switches, hubs and so on. Network layer

The data in the transport layer is encapsulated into data packets in a fixed format. The source IP address and destination IP address are encapsulated in the packet. The network layer chooses the best path based on the IP address of the header of the packet and sends it. The main equipment is router and so on. Transport layer

The transport layer is mainly to achieve end-to-end communication. The protocols at the transport layer are TCP and UDP. TCP provides reliable data transmission but does not guarantee efficiency, while UDP provides efficient data transmission but is not reliable. Session layer

The main function of the session layer is to establish, manage and terminate the session. Presentation layer

The main functions of the presentation layer are data representation, security and compression. Application layer

The application layer is mainly user interaction.