A fault tolerant@ real time high speed data communication standard is defined based on a ring topology and the use of a Token passing access method with distributed control. The requirements for the HSRB standard have been driven predominantly@ but not exclusively@ by military applications. Particular attention has been given to the need for low message latency@ deterministic message priority and comprehensive reconfiguration capabilities. This document contains a definition of the semantics and protocol including delimiters@ tokens@ message priority@ addressing@ error detection and recovery schemes; and is written to be independent of bit rate and media. Parameters related to particular media and bit rates are defined in separate documents@ the AS4075 slash sheets.