Achieving differentiated services through multi - class 3 probabilistic priority scheduling 4

11 Differentiated services (DiffServ) is a promising architecture for the next generation Internet due to its scalable and 12 flexible design. In DiffServ, scheduling disciplines play an important role in achieving service differentiation. In this 13 paper, we extend the average delay analysis of the probabilistic priority (PP) scheduling discipline first proposed in 14 [Proc. 2001 IEEE Workshop on High Performance Switching and Routing (HPSR 2001), 2001] to the multi-class case. 15 The PP discipline is based on the strict priority discipline with the difference that each priority queue is assigned a 16 parameter pi 2 1⁄20; 1 which determines the probability that the queue is served. We derive the relationship between the 17 average queueing delay of each class and these parameters, as well as the upper and lower bounds of the average 18 queueing delay for each class. This relationship shows that PP can provide different quality of service (QoS) to different 19 priority classes in a controllable way. Simulation results are presented to assess the validity of these findings in different 20 scenarios, e.g. different traffic types, offered traffic loads and parameterizations. We also specifically address the issues 21 concerning the use of the PP discipline in DiffServ networks to achieve different per-hop-behaviors and describe the 22 performance of a Linux implementation of PP running on a DiffServ testbed. Finally, we evaluate the ability of the PP 23 discipline to provide relative and proportional DiffServ. 2002 Published by Elsevier Science B.V.