Scalable flow control for multicast ABR services

Abstract

We propose a flow control scheme for multicast ABR services in ATM networks. At the heart of the proposed scheme is an optimal second-order rate control algorithm, called the /spl alpha/-control, designed to deal with the variation in RM-cell round-trip time (RTT) resulting from dynamic "drift" of the bottleneck in a multicast tree. Applying two-dimensional rate control, the proposed scheme makes the rate process converge to the available bandwidth of the connection's most congested link. It also confines the buffer occupancy to a target regime bounded by a finite buffer capacity. It works well irrespective of the topology of the multicast tree. Using the fluid approximation, we model the proposed scheme and analyze the system dynamics for multicast ABR traffic. We study the convergence properties and derive the optimal control conditions for the /spl alpha/-control. The analytical results show that the scheme is stable and efficient in the sense that both the source rate and bottleneck queue length rapidly converge to a small neighborhood of the designated operating point. We present simulation results which verify the analytical observations. The simulation results also demonstrate the effectiveness of the proposed scheme in dealing with RM-cell RTT and link-bandwidth variations, and in achieving fairness in both buffer and bandwidth occupancies.