Performance analysis of token ring networks with reservation priority discipline

A token ring network is considered, with priority-mode operation by a reservation discipline which is adopted by an IEEE standard 802.5. In the reservation discipline, a high-priority station can reserve the next transmission right in the reservation field of the message transmitted by the low-priority station when the reservation field passes through the high-priority station. Then the free token at the high-priority level is passed to the high-priority station. After all messages from the high-priority stations are transmitted, the free token is returned to the station in the downstream of the previous low-priority station. To apply this reservation discipline to an interconnected token ring network system, an analytical model is constructed which consists of low-priority stations with single buffer and a single high-priority station with infinite buffer, which is intended to represent a bridge. An exact analysis for the low-priority stations and an approximate analysis for the high-priority station in the reservation discipline is presented. System performance measures (mean waiting times and throughput) derived from the present analysis are compared with a mixed discipline which is an alternative method for priority-mode operation in token ring networks