OSI protocols

• The Open Systems Interconnection (OSI) protocols are a family of information exchange standards developed jointly by the ISO and the ITU-T starting in 1977.
• While the seven-layer OSI model is still often referenced, of the protocols themselves only X.400, X.500, and IS-IS have had much lasting impact. 
• The goal of a series of open, non-proprietary network protocols is now met by the competing TCP/IP stack.

OSI protocols stacks are split into seven layers.