OSI layer Seven Protocol

OSI is an abbreviation for open System interconnection, meaning open Systems interconnection, the International Organization for Standardization (Iso,international Organization for Standardization) developed the OSI model, The model defines the standards of interconnection of different computers and is the basic framework for designing and describing computer network communication.

① Physical layer: to give electrical characteristics to send high and low voltage (electrical signal), higher voltage corresponding to the number 1, low voltage corresponding to the number 0

Repeater, hub, twisted pair

② Data Link layer: Defines the grouping of electrical signals, a set of data packets called frames, a frame divided into header head and data two parts

Head part fixed 18 bytes, sender/Source address 6 bytes, receiver/Destination address 6 bytes, data type 6 bytes

The source and destination addresses are the MAC addresses of the NIC, typically in 12-bit hexadecimal digits

Network Bridge, network card, Ethernet switch

③ Network layer: Referencing network addresses to differentiate between broadcast domains and subnets

Protocols include IP, ARP, RARP, ICMP, IGMP, etc.

IP address packets are also divided into head and data sections

Head length is 20-60 bytes

Routers, layer three switches

④ Transport Layer: Port-to-port communication, with a port number range of 0-65535

Protocol has TCP, UDP

Four-layer switch, four-layer exchanger

⑤ Session Layer: establishing, terminating, and managing sessions

⑥ Presentation layer: Format representation of data, compression and decompression, encryption and decryption

⑦ Application layer: an interface between Web services and end users

Protocols are HTTP, HTTPS, FTP, SFTP, DNS, Telnet, POP3, DHCP, SMTP, SNMP, etc.

OSI layer Seven Protocol