Open Systems Interconnection Specification

In telecommunication, Open Systems Interconnection Specification (OSI)--Protocol is the lowest level of abstraction within the OSI standards scheme.

Note: Each OSI--Protocol Specification operates at a single layer. Each defines the primitive operations and permissible responses required to exchange information between peer processes in communicating systems to carry out all or a subset of the services defined within the OSI--Service Definitions for that layer.

Source: from Federal Standard 1037C

See also OSI model