Open Systems Interconnection model (OSI model)


This page is about the OSI model that describes the layers of the internet for data transmission.

The level 5 (session) and 6 (presentation) are nowadays implemented in the level 7 (application) and above

Level Name Data unit Description Protocol
7 Application layer Message Higher level (Resource Sharing, Remote file access, …) HTTP, SMTP, FTP, DHCP, DNS, Telnet, SNMP, …
6 Presentation layer Message Data Translation (Character encoding, data compression and encryption/decryption) MIME, XDR, ASN.1, ASCII, PGP
5 Session layer Message Session functionality Named pipe, NetBIOS, SAP, PPTP, RTP, SOCKS, SPDY, X.225
4 Transport layer Segment / Datagram Data transmission between network point TCP, UDP, SCTP, DCCP, SPX
3 Network layer Packet Addressing, routing and traffic control IP, ICMP, IPsec, IGMP, IPX, IS-IS, Apple Talk, X.25, PLP
2 Data link layer Frame Frames transmission between two physical nodes connected ATM, ARP, …
1 Physical layer Bit, Symbol Raw bit transmission over a physical medium IEEE 802.3 (Ethernet cable), IEEE 802.11 (Wifi), USB, Bluetooth, Rs232 (modem, printer, …)

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