Token-based protocols for high-speed optical-fiber networks

The local network medium is a pair of unidirectional fiber-optic busses to which stations are connected via passive taps. For this configuration, we present several protocols which provide round-robin, bounded delay access to all stations, and are particularly suited for high-speed transmission. The common characteristic of the protocols is the use of the token as the synchronizing event to schedule transmission. The token may be explicit (as in U-Net) or implicit (as in Tokenless Net). It may be used all the time, or it may be used simply to resolve collisions (as, in Buzz-Net). The protocols are shown to be cost effective at very high (bandwidth)x(length) products that are the unique characteristic of high-speed single-mode fiber networks. Furthermore, they are robust to failures because of the passive interfaces and the totally distributed control. The implementation of these protocols on fiber-optic busses is also discussed in the paper.