A theory of window-based unicast congestion control

We present a comprehensive theoretical framework for window-based congestion control protocols that are designed to converge to fairness and efficiency. We first derive a sufficient condition for convergence to fairness. Using this, we show how fair window increase/decrease policies can be constructed from suitable pairs of monotonically non-decreasing functions. We show that well-studied protocols such as TCP, GAIMD (general additive-increase multiplicative-decrease) and binomial congestion control can be constructed using this method. Thus we provide a common framework for the analysis of such window-based protocols. To validate our approach, we present experimental results for a new TCP-friendly protocol, LOG, designed using this framework with the objective of reconciling the smoothness requirement of streaming media-like applications with the need for a fast dynamic response to congestion.