A comparative study of synchronous and nonsynchronous transmission algorithms on a replicated token bus network

Two token management algorithms are proposed: synchronous and nonsynchronous transmission. In a synchronous dual redundant system, all tokens being rotated in the network, one for each channel, are passed between the two stations within some given period of time. Tokens and messages transmitted are synchronized since the time skews take place only within the adjacent stations. This is achieved by waiting for the slower channel in each path. For a nonsynchronous dual redundant network, tokens are passed to the next station independently of the other bus token. Unlike the synchronous scheme, therefore, time skew is not bounded within each path, but rather it is additive. The model of a nonsynchronous transmission network is identical to the model of multiple single channels operating freely except in the case of message arrival. Comparisons of the two algorithms are made through studies of the speed performance parameter and the maximum buffer capacities required, along with the level of the design complexity involved in the development of each of the algorithms