Design of controller for XCP router achieving efficient and fair bandwidth allocation

As the product of bandwidth and latency increases, TCP becomes inefficient and prone to instability, regardless of the queuing scheme. The eXplicit Control Protocol (XCP) is a novel and promising congestion control protocol that outperforms TCP in terms of efficiency, fairness, persistent queue length, packet loss rate and convergence speed. However, in a multi-bottleneck environment, XCP may cause some bottleneck links to be under-utilized, and a flow may only receive a small fraction of its max-min fair allocation. In this paper, according to the robust control theory, with the help of a recently developed Lyapunov-Krasovskii functional, we propose an XCP bandwidth compensation algorithm based on state feedback (S-XCP). Extensive simulations have shown that S-XCP achieves efficient and fair bandwidth allocation in a multi-bottleneck environment. Simulations also have shown that S-XCP preserves the good properties of XCP, including fast convergence, low persistent queue length and negligible packet loss rate.