2 VACATION MODELS FOR TOKEN-RING NETWORKS WHERE SERVICE IS CONTROLLED BY TIMERS

Two vacation models with constant time-limited service and vacation-dependent, time-limited service are proposed for the performance analysis of stations in timed-token networks (e.g., FDDI and IEEE 802.4 token bus). By the use of exponential time stages to approximate the constant time limits, the matrix analytic method is applied to solve the vacation models for the queue length distribution and the moments of the sojourn time. Our results reveal that, even at high loads, the approach of time stages converges rapidly to the actual cases of constant time limits. The proposed solution method is efficient and numerically stable' Furthermore, the model apply not only to the timed-token networks, but also to other systems where service is controlled by timers.