Establishes definitions of terms and conventions for reference by Standards defining the connection-oriented or connectionless-mode (N)-services provided by the Reference Model for Open Systems Interconnection (AS 2777). In particular, it is concerned with conventions relating to a point-to-point connection, or instance of a point-to-point communication within a layer of the Reference Model. This Standard is identical with and has been reproduced from ISO/TR 8509:1987.