Queue scheduler: a comparative study for telephony over IP scenarios

This paper presents a method for managing edge queues in Telephony over IP (ToIP) scenarios. We introduced a Call Admission Control (CAC) algorithm, called QoS-Weighted CAC, and evaluate the difference in performance achieved by different Queue management configurations to guarantee Quality of Service to telephony applications. Our goal was to evaluate the weight of edge router queue configuration in complex and real-like telephony over IP scenario. This scenario presents different traffic services characterized by specific real-time requirements, which need a differentiated management of packet flows. In order to reach this goal, we used a measurement-based call admission control algorithm, which detects network congested links through a feedback on overall link utilization, as a common environment for analyzing the effects of queue configuration. In this way we introduce a close loop control method, which is able to auto-adapt the quality margin on the basis of network load and specific service level requirements. By means of software simulations and analytical models we want to compare many well-know queue scheduling algorithms, such as SFQ, WRR, RR, WIRR, and Priority. This comparison aims to locate queue schedulers in a more general control scheme context where different elements such as DiffServ marking and Admission control algorithms contribute to the overall Quality of Service required by real-time voice conversations. On the basis of the results we try to evidence the potential advantages of these Queue management solutions in comparison with other similar solutions, on the planes of complexity, stability, management, tune-ability to service level requirements, and compatibility with actual network implementation.