Performance analysis of fair schedulers under heterogeneous traffic

Abstract

In this thesis, the role of the packet scheduling discipline has been studied in providing QoS over the Internet. The fairness and scalability requirements expected to be satisfied by the scheduling discipline have been analysed, with reference to the two categories under which schedulers are broadly classified: Round-robin-based schedulers and Timestamp-based schedulers. In particular, the basic principles and design goals of three specific Fair Schedulers WDRR, NestedDRR and StratifiedRR have been studied. The Network Simulator (ns-2) tool has been enhanced to support WDRR, NestedDRR and StratifiedRR schedulers. To analyse the performance of WDRR, NestedDRR and StratifiedRR under MPEG, CBR and BE traffic, simulations have been carried out for specific load conditions under single hop and two hop topologies. From simulation results it has been observed that, as its reserved rate increases, MPEG traffic achieves better performance under StratifiedRR. Also, degradation in the performance received by other contending traffics is greater under StratifiedRR. It has been identified that, for fixed value of Load Factor, as quantum increases, the End-to-End delay and End-to-End delay-jitter of MPEG traffic under WDRR show greater variation than that seen under NestedDRR. Based on these results, an improvement over StratifiedRR has been proposed which is expected to make the delay and delay-jitter seen by a flow independent of the packet sizes in other flows.