The Cambridge Backbone Ring

An experimental ring communication network, the Cambridge Backbone Ring, for integrated computer data, voice, and real-time video applications is described. The network is aimed as a backbone facility for interconnecting groups of Cambridge Fast Ring (CFR) networks in the Cambridge area. Media access control is through the empty slot technique, with transmitting stations filling multiple slots each ring revolution. The network operates on monomode optical fiber and is designed for an eventual line rate of 1000 Mb/s. In the backbone ring architecture, the bandwidth of the fiber-optic channel can be partitioned into a number (currently four) of time division multiplexing (TDM) channels. This enables stations of varying cost and bandwidth to be attached to one network, parameterized by the number of channels a station can use concurrently. The backbone ring architecture achieves full connectivity, even with the simplest type of station. Some brief traffic simulation results are presented