five-layer computer network protocol
1. Application layer
Task : Complete a specific network application through the interaction between application processes. The application layer defines the rules for communication and interaction between application processes.
For example: HTTP SMTP FTP
2. Transport layer
Task : Responsible for providing common data services for communication between processes in two hosts.
The following two protocols are mainly used:
Transmission Control Protocol TCP : Provides connection-oriented and reliable data transmission services, and the unit of data transmission is the segment .
User Datagram Protocol UDP : Provides a connectionless best-effort data transmission service (does not guarantee the reliability of data transmission) The unit of data transmission is the user datagram
Network layer
Task 1 : Responsible for providing communication services for different hosts on a packet-switched network. When sending data, the network layer encapsulates the segments and user datagrams generated by the transport layer into packets ( IP datagrams ) or packets for transmission. Task 2 : Choose an appropriate route so that the packets from the source host's transport layer can find the host through the router.
data link layer
Task : When data is transmitted between two adjacent nodes, the data link layer assembles the IP datagrams handed over by the network layer into frames, and transmits frames on the two adjacent links . Each frame includes data and necessary control information.
physical layer
The unit of data transmitted by the physical layer is a bit . The physical layer considers what voltage to use to represent a 1 or 0, and how the receiver recognizes the bits sent by the sender.