A concept, defined in ANSI standards, for an optical-fiber-based token-ring network, featuring (a) dual counter-rotating logical rings, each with a data transmission capacity of 100 Mb/s, (b) reliable data transfer, (c) active link monitoring, (d) station management, and (e) survivability features. Note 1: The four standards are (a) ANSI X3T9. 5, containing Physical Media Dependent (PMD) specifications, (b) ANSI X3T9. 5, containing the Physical (PHY) specifications, (c) ANSI X3. 139, containing Media Access Control (MAC) specifications, and (d) ANSI X39. 5, containing the Station Management (SMT) specifications. Note 2: The data rate of an FDDI ring may be doubled to 200 Mb/s, with loss of redundancy. Note 3: FDDI-2, a second-generation FDDI network standard, is under development.