On the robustness of AQM mechanisms against non-responsive traffic

Active Queue Management (AQM) mechanisms have come a long way, with an initial goal to avoid congestion to the recent most focus on reducing queue delay. The benefits of using AQM mechanisms at routers are being thoroughly studied nowadays, mainly to avoid the problem of bufferbloat. Although a lot of work has focused on analyzing the behavior of AQM mechanisms, the nature of traffic used while deriving inferences is mainly responsive (TCP), with small numbers of unresponsive flows (UDP) used in the background. The usage of UDP in Internet has increased significantly in the recent past, owing to a great demand for time sensitive multimedia applications. Since UDP flows do not respond to congestion signals, controlling the queue length at routers by using AQM mechanisms becomes a non-trivial task. In this paper, we study the robustness of popular AQM mechanisms in the presence of a large number of unresponsive UDP flows using ns-2. Further, we provide guidelines to effectively tune the AQM knobs and enhance their robustness against non-responsive UDP flows.