Conservative parallel simulation of priority class queuing networks

A conservative synchronization protocol for the parallel simulation of queuing networks having C job priority classes, where a job´s class is fixed, is described. This problem has long vexed designers of conservative synchronization protocols because of its seemingly poor ability to compute lookahead: the time of the next departure. For, a job in service having low priority can be preempted at any time by an arrival having higher priority and an arbitrarily small service time. The solution is to slow the event generation activity so that events for higher priority jobs are generated farther ahead in simulated time than lower priority jobs. Thus. when a lower priority job enters service for the first time, all the higher priority jobs that may preempt it are already known and the job´s departure time can be exactly predicted. The author analyzes the protocol and demonstrates that good performance can be expected on the simulation of large queuing networks