Exogenous-loss aware traffic management in overlay networks : Toward global fairness

For a given TCP flow, exogenous losses are those occurring on links other than the flow’s bottleneck link. Exogenous losses are typically viewed as introducing undesirable “noise” into TCP’s feedback control loop, leading to inefficient network utilization and potentially severe global unfairness. This has prompted much research on mechanisms for hiding such losses from end-points. In this paper, we show that low levels of exogenous losses are surprisingly beneficial in that they improve stability and convergence, without sacrificing efficiency. Based on this, we argue that exogenous-loss awareness should be taken into account in overlay traffic management techniques that aim to achieve global fairness. To that end, we propose an eXogenous-loss aware Queue Management (XQM) approach that actively accounts for and leverages exogenous losses on overlay paths. We envision the incorporation of XQM functionality in Overlay Traffic Managers (OTMs). We use an equation based approach to derive the quiescent loss rate for a connection based on the connection’s profile and its global fair share. In contrast to other techniques, XQM ensures that a connection sees its quiescent loss rate, not only by complementing already existing exogenous losses, but also by actively hiding exogenous losses, if necessary, to achieve global fairness. We establish the advantages of exogenous-loss-aware OTMs using extensive simulations in which we contrast the performance of XQM to that of a host of traditional exogenous-loss unaware techniques.