OSI layer (7) : physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer. TCP/IP layer (four layers) : network interface layer, Internet layer, transport layer, and application layer. Layer 5 protocol: physical layer, data link layer, network layer, transport layer, and application layer.
1) Physical layer: the transmission medium is used to provide physical connection for the data link layer to realize the transparent transmission of bitstream
2) Data link layer: through various control protocols, the physical channel with errors is transformed into an error-free data link capable of transmitting data frames reliably
3) The network layer provides routing and addressing functions, so that the two terminal systems can be interconnected and determine the best path, and has certain congestion control and flow control capabilities.
4) Transmission layer: provide users with reliable end-to-end error and flow control to ensure the correct transmission of packets. The function of the transport layer is to shield the details of the data communication from the upper layer, that is, to transparently transmit messages to users
5) Session layer: The task is to provide the presentation layer of two entities with the means to establish and use the connection.
6) Presentation layer: it interprets commands and data from the application layer, endows various grammars with corresponding meanings, and transmits them to the session layer in a certain format
7) Application layer: The application layer provides the following services and protocols for users: file service, directory service, file transfer service (FTP), remote login service (Telnet), E-mail service (E-mail), printing service, security service, network management service, database service, etc
Differences between transport layer and network layer:
The agreement for each layer is as follows: