A reliable and parallel double-ring FDDI metropolitan area network

The authors present a reliable double-ring metropolitan area network architecture, called DORFMAN, based on an enhanced Fiber Distributed Data Interface (FDDI) protocol. DORFMAN is composed of two local ring networks interconnected via two monitors. The two monitors are used to perform simple routing and error recovery logic as well as mode transitions of DORFMAN. There are three modes defined in DORFMAN: local, global, and transition modes. During the local mode, DORFMAN allows double rings to operate in parallel. During the global mode, DORFMAN behaves as an FDDI network. Modes are dynamically switched between local and global modes on a demand basis. The bandwidth waste resulting from the transition of modes has been reduced to a minimum. Performance analysis and simulation results show that with a reasonable degree of locality assumed, twice the throughput of an FDDI network can be achieved in DORFMAN. An error recovery scheme for DORFMAN is addressed