S-XCP: Improving XCP to Achieve Efficient and Fair Bandwidth Allocation

The eXplicit Control Protocol (XCP) was developed to overcome the limitations of TCP, such as unstable throughput, low utilization, limited fairness, and large persistent queue length. However, Low proves that the XCP equilibrium solves a constrained max-min fairness problem, in a multi-bottleneck environment, XCP may cause some bottleneck links to be underutilized, and a flow may only receive a small fraction of its maxmin fair bandwidth allocation. To address this problem, Zan proposes an improved version of XCP (iXCP), which shuffles bandwidth only among flows that are bottlenecked at current routers. 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). The synthesis problem is reduced to a convex optimization scheme expressed in terms of linear matrix inequalities (LMI). Extensive simulations have shown that S-XCP achieves efficient and fair bandwidth allocation in a multi-bottleneck environment. Compared with iXCP, (1)S-XCP have the same packet header overhead of XCP; (2)computing complexity significantly declines; (3)and more effective control in highly dynamic situations.