Improving the stability of eXplicit Control Protocol under heterogeneous delays

The eXplicit Control Protocol (XCP) is a promising congestion control protocol that outperforms TCP in terms of efficiency, fairness, persistent queue length, and packet loss rate. However, XCP will behave in a noticeably unstable manner if the maximum round trip time of a flow is much larger than average round trip time of all flows, which is a typical nonlinear instability. In this paper, eXCP is proposed to stabilize the system and enable XCP to deal with heterogeneous feedback delays. With the aid of the exponentially weighted moving average filter, eXCP directly reduces the volatility of the control interval and effectively improves the stability of the aggregate input traffic at a bottleneck link. Simulations also have shown that the variance of per-flow throughput and round trip time decrease dramatically.