A packet queueing engine for configurable network QoS

Packet scheduling is key to QoS capabilities of broadband wired and wireless networks. In a heterogeneous traffic environment, a comprehensive QoS packet scheduler must strike a balance between flow fairness and access delay. Many advanced packet scheduling solutions have targeted fair bandwidth allocation while protecting delay-constrained traffic by adding priority queue(s) on top of a fair bandwidth scheduler. Priority queues are known to cause performance uncertainties and thus various modifications have been proposed. In this paper, we present a packet queueing engine dubbed Fractional Service Buffer (FSB) which, when coupled with a configurable flow scheduler, can achieve desired QoS objectives such as fair throughputs and differentiated delay guarantees. The flow scheduler is a buffer-less module that can be configured to assign each incoming packet a delay class in accordance with its owner flow's QoS status. The FSB uses one buffer for each delay class and serves the buffers with a special queueing discipline that advances packets in lower-priority buffers to meet their class-specific delay guarantees. Key performance metrics such as delay limit and probability of delay limit violation are derived, as a function of key FSB parameters, for each delay class in the packet queueing engine using diffusion approximations. OPNET simulations verify these analytical results.