Iso/osi model
The OSI seven-layer framework acts on the application layer: the layer presentation layer of the user operation: the conversion between the binary data and the display data, and also the encrypted local session layer: determining whether the network is transmitted or stored locally, whether it is a transport layer such as mail or PPT: Determine TCP or UDP protocols, and outgoing and incoming ports; FTP has different ports; TCP protocol is more stable, UDP is faster, but not reliable network layer: Determine the outgoing and incoming IP address data link layer: Determine the MAC address, transfer data physical layer in each LAN: Transfer binary Data # The port number of the network service is 80, the port number of the message transfer is 25 and 110, The port number of the file transfer is 21
Network Foundation of Linux Network management