Mean sojourn time in a parallel queue

This account considers a parallel queue, which is two-queue network, where any arrival generates a job at both queues. It is noted that earlier work has revealed that this class of models is notoriously hard to analyze. We first evaluate a number of bounds developed in the literature, and observe that under fairly broad circumstances these can be rather inaccurate. For the 'homogeneous' case we present a number of approximations, which are extensively tested by simulation, and turn out to perform remarkably well.