Applicable to end systems and relay systems operating over FDDI LAN subnetworks in the Open Systems Interconnection (OSI) environment. Specifies the subnetwork-type dependent requirements for the MAC, PHY and PMD sublayers, and the Station Management function when the end system or relay system is attached to an FDDI LAN subnetwork. Relates to any of the transport (Tx, Ux) or relay (Rx) profiles defined in ISO/IEC TR 10000-2, Taxonomy of OSI Profiles, where such profile uses subnetwork type 54 (FDDI Local Area Network). Specifically, provides a common set of FDDI subnetwork requirements whenever subnetwork identifier 54 is associated with a transport group or relay type.