Overlay QoS with Closed-Loop Flow Control

Shivkumar Kalyanaraman

Rensselaer Polytechnic Institute, USA


Traditionally QoS capabilities have been constructed out of open-loop building blocks such as packet schedulers and traffic conditioners. In this paper, we consider closed-loop techniques to achieve a range of service differentiation capabilities. Our key contribution is the use of a new class of congestion control schemes, Accumulation-based Congestion Control (ACC) as a data-plane building block to provide an expected minimum rate service which is similar to Frame Relay CIR/PIR and DiffServ assured service. Instead of attempting optimization with non-concave objective functions, we demonstrate a meaningful notion of an expected minimum rate by imposing additional constraints on Kellys convex optimization. Unlike the constraint which simply requires all user allocations to be larger than their respective expected minima, our constraint does not require admission control. The resulting scheme is distributed, requires each control loop to act only on local knowledge and still allows policy-based control over how capacity is allocated during oversubscription. We use ns-2 simulations and Linux implementation experiments to demonstrate that the service performance matches theoretical results. Our scheme does not require Active Queue Management (AQM) at bottlenecks. However, with an AQM approach like AVQ and virtual delay concept, we achieve near zero queue with high utilization. This system offers the attractive prospect of overlaying QoS capabilities over a network of existing routers.

[Shivkumar Kalyanaraman]
[Rensselaer Polytechnic Institute, USA]