Linear Stability Analysis of FAST TCP Using A New Accurate Link Model

A link model which captures the queue dynamics when congestion windows of TCP sources change was recently proposed. By considering both the self-clocking and the link integrator effects, the model is a generalization of the known extreme cases and is more accurate in general. In this paper, we apply this model to the stability analysis of FAST TCP. It is shown that FAST TCP flows over a single link are always linearly stable regardless of delay distribution. This result resolves the notable discrepancy between empirical observations and previous theoretical predictions. The analysis highlights the critical role of self-clocking in TCP stability and the scalability of FAST TCP with respect to delay. The proof technique is new and much less conservative than existing ones.