Analysis of adaptive rate-based congestion control for high-speed wide-area networks

Considers an approach to controlling congestion in high-speed wide-area networks which combines open-loop rate-based controls and feedback. In rate-based controls the allowable traffic characteristics of a connection are determined during the call set-up process based on the currently available resources, and are monitored and enforced in real-time using access regulators. To utilize resources that might become available during the connection holding time due to changing traffic conditions, the author proposes an algorithm for the dynamic adaptation of the access regulator parameters based on feedback information on the buffer status of bottleneck nodes. By proper tuning of the control parameters, the algorithm overcomes the challenges paused by the significant propagation delays in these networks. The algorithm is represented by coupled delay-differential equations and the criteria for asymptotic (oscillation-free) stability are derived in terms of the control parameters (gain and damping constants) and round-trip propagation delays. The steady state throughput and queueing delays for a given connection are determined and the dynamic range over which the output of the access regulator tracks available channel rates is obtained. The time constant of adaptation and the control parameter setting to achieve optimal transient behavior are derived. Numerical results demonstrate the effectiveness of the algorithm and illustrate the tradeoffs between the steady state throughput and queueing delays, the dynamic range and the time-constant of adaptation