Black Box Explains...Networking with Token Ring.
Token Ring was developed in the early 1980s by IBM®. In 1985, the IEEE released document number 802.5, which formally accepted Token Ring as a standard. Although its popularity has been eclipsed by Ethernet, Token Ring is nonetheless a robust networking standard and is still operating reliably in many legacy networks.
Token Ring is most often used in IBM mainframe environments. IBM provides Token Ring connections on much of its mainframe computer hardware, and its software enables PCs and mainframes to act as peers on the same network.
The name “Token Ring” is somewhat misleading. Although its name implies a physical ring shape, Token Ring is actually a star-based topology. Logically, the network operates as a ring— “tokens” bearing information are passed from node to node until the token travels completely around the ring. The star-shaped topology makes moving, changing, and adding equipment quick and easy.
Token Ring is fault tolerant. If, for example, the cable to one of your networked PCs is damaged or cut, the MAU automatically bypasses that port. Because the logical ring stays intact, your network stays up.
But although it’s proven to be reliable and fault-tolerant, Token Ring has largely been supplanted by Ethernet, and Token Ring network devices are no longer widely available.