Throughput analysis of a timer controlled token passing protocol under heavy load

An analysis is presented of the throughput performance of some recently proposed token-passing local area network (LAN) protocols under a heavy load assumption. The IEEE 802.4 token bus standard which uses a cycle-dependent timing mechanism to control station access to the channel, is studied. It is shown that the cycle-dependent timing mechanism limits the token circulation times properly. Moreover, priority among different access classes is being implemented. Analytic results for computations of throughputs and cycle lengths are derived. These results provide insights into the cycle-dependent timing mechanism and also guidelines for design. Using the results derived, examples concerning the throughput behavior under different heavy load configurations, the sensitivity to parameters, system optimization with delay and bandwidth constraints, and comparison with the other integrated access schemes are studied