3-computer network reference model

1. OSI

The International Standards Organization (ISO) issued the Open Systems Interconnection reference Model (OSI) in 1984.

Second, the meaning of OSI seven-layer model.

Application layer: an excuse for the Network to serve the end user

Presentation layer: data representation, security, compression

Session layer: establish, manage, and terminate sessions such as breakpoint continuation

Transport layer: define the protocol port number for transmitting data, as well as flow control and error checking to realize the interconnection of programs.

Network layer: logical address addressing, path selection between different networks, and IP address is defined as the best path for data transmission.

Data link layer: establish logical connection, perform hardware address addressing, error checking and other functions, realize communication and frame transmission through MAC address

Physical layer: establish, maintain, disconnect physical connections, define interfaces and media, and realize the transmission of bitstreams

III. Composition of the TCP/IP protocol family

Common protocols:

Application layer: FTP HTTP TFTP SMTP SNMP DNS TELNET POP3 HTTPS

Transport layer: TCP UDP

Network layer: ICMP IGMP IP ARP RARP

IV. The process of data transmission

The process of data encapsulation and unencapsulation

5. PDU (Protocol data Unit)

Transport layer segment segment

Network layer packet packet

Data Link layer frame Fram

Physical layer bit bit