Control Theoretic Analysis of eXplicit Control Protocol with Short-Lived Traffic

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. XCP quantitatively informs senders how to adjust their sending rate, and assumes that all senders will respond. However, short-lived flows are often on the order of a few segments, they may be unresponsive to XCP feedback, and have negative impact on the system control loop. In this paper, a control theoretic analysis of the XCP properties is conducted in the presence of short-lived traffic. First, the original XCP model is modified to account for these unresponsive flows. Then, with the M/G/∞ model of short-lived traffic, their impact on the XCP control loop is analyzed, and theoretical results show that short-lived bursty traffic have the effect of reducing the available bandwidth and increasing the variances of long-lived XCP flows. Finally, theoretical results are verified using packet level simulations.