GPS scheduling : selection of optimal weights and comparison with strict priorities

We consider a system with two service classes with heterogeneous traffic characteristics and Quality-of-Service requirements. The available bandwidth is shared between the two traffic classes in accordance with the Generalized Processor Sharing (GPS) discipline. GPS-based scheduling algorithms, such as Weighted Fair Queueing, provide a popular mechanism for service differentiation among heterogeneous traffic classes. While the performance of GPS for given weights has been thoroughly examined, the problem of selecting weight values that maximize the traffic-carrying capacity, has only received limited attention so far. In the present paper, we address the latter problem for the case of general Gaussian traffic sources. Gaussian models cover a wide variety of both long-range dependent and short-range dependent processes, and are especially suitable at relatively high levels of aggregation. In particular, we determine the realizable region, i.e., the combinations of traffic sources that can be supported for given Quality-of-Service requirements in terms of loss and delay metrics. The results yield the remarkable observation that simple priority scheduling strategies achieve nearly the full realizable region.