Improving Robustness of XCP (eXplicit Control Protocol) for Dynamic Traffic

In this paper, we reveal inherent robustness issues of XCP (eXplicit Control Protocol), and propose extensions to XCP for increasing its robustness. XCP has been proposed as an efficient transport-layer protocol for wide-area and high-speed network. XCP is a transport-layer protocol that performs congestion control based on explicit feedback from routers. In the literature, many performance studies of XCP have been performed. However, the effect of traffic dynamics on the XCP performance has not been fully investigated. In this paper, through simulation experiments, we first show that XCP has the following problems: (1) the bottleneck link utilization is lowered against XCP traffic dynamics, and (2) operation of XCP becomes unstable in a network with both XCP and nonXCP traffic. We then propose XCP-IR (XCP with Increased Robustness) that operates efficiently even for dynamic XCP and non-XCP traffic. key words: XCP (eXplicit Control Protocol), traffic dynamics, robustness, stability, congestion control