OSI protocols

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The Open Systems Interconnection protocols are a family of information exchange standards developed jointly by the ISO and the ITU-T. The standardization process began in 1977.

OSI model
by layer
7.  Application layer
6.  Presentation layer
5.  Session layer
4.  Transport layer
3.  Network layer
2.  Data link layer
1.  Physical layer

While the seven-layer OSI model is often used as a reference for teaching and documentation,[2] the protocols originally conceived for the model did not gain popularity, and only X.400, X.500, and IS-IS have achieved lasting impact. The goal of an open-standard protocol suite instead has been met by the Internet protocol suite, maintained by the Internet Engineering Task Force (IETF).