Simple Analysis of XCP Equilibrium Performance

The recently developed explicit control protocol (XCP) is a congestion control system well suited for high bandwidth delay product (BDP) networks. Low proves that the XCP equilibrium solves a constrained max-min fairness problem, and derives the explicit formulas for the link utilization and the common flow rate bottlenecked at the link by applying the derived window-based dynamic model. Furthermore, a lower bound and an upper bound of link utilization are given in Low's paper. However, the derived window-based dynamic model is so complicated that it can not be used easily. In this paper, a simple rate-based model is proposed for analyzing XCP equilibrium performance. Most results that appeared in Low's paper can be easily reproduced by applying our simple dynamic model. Furthermore, we prove that the shuffling parameter gamma is no more than the parameter alpha to achieve high link utilization.