A high-performance scheduler to achieve proportional delay differentiation

The proportional delay differentiation model provides a consistent packet delay differentiation between various classes of service. The waiting time priority (WTP) scheduler is a priority scheduler in which the priority of a packet increases in proportion to its waiting time, and it is known as the best scheduler to achieve proportional delay differentiation model. This paper proposes an advance WTP (AWTP) scheduler, modified from WTP, which accounts for the packet transmission time. Simulation results reveal that when the link utilization is moderate (60%-90%), this scheduler not only obtains more accurate delay proportion than the WTP scheduler, but also reduces the average queuing delay (waiting time). The effects of traffic load distribution are also examined. However, AWTP may not maintain stable delay ratios under various traffic load distributions. A modification named AWTP⁺ is proposed and proven to relieve this problem.