Improving Performance Bounds for Weighted Round-Robin Schedulers under Constrained Cross-Traffic

Weighted round robin (WRR) is a simple, efficient packet scheduler providing low latency and fairness by assigning flow weights that define the number of possible packets to be sent consecutively. A variant of WRR that mitigates its tendency to increase burstiness, called interleaved weighted round robin (IWRR), has seen analytical treatment recently [1]; a network calculus approach was used to obtain the best-possible strict service curve. From a different perspective, WRR can also be interpreted as an emulation of an idealized fair scheduler known as generalized processor sharing (GPS). Inspired by profound literature results on the performance analysis of GPS, we show that both, WRR and IWRR, belong to a larger class of fair schedulers called bandwidth-sharing policies. We use this insight to derive new strict service curves for both schedulers that, under the additional assumption of constrained cross-traffic flows, can significantly improve the state-of-the-art results and lead to smaller delay bounds.