Queuing dynamics and single-link stability of delay-based window congestion control

Accurate modeling of queueing dynamics is important in the design and analysis of Internet congestion control. However, as demonstrated in this paper, existing window-based queueing models [26] and [30] are often not capable of precisely capturing the transient behavior (i.e., self-clocking and burstiness) of TCP-like protocols and their resulting analysis may be inaccurate in practice. As one example, we show that stability conditions of FAST TCP based on traditional queuing models [17] that do not considering transient dynamics of the queues are inconsistent with ns2 simulations. We explain the origin of this problem and overcome it by developing a novel approach called Self-clocking Queuing Model (SQM) that accurately describes both the steady-state and transient queuing behavior of window-based control systems. Using SQM and explicitly incorporating control interval hihi in the queuing model and derive a sufficient condition for its local stability under homogeneous delay, which strengthens prior results [29] and [30] obtained using traditional queuing models.