Distributed max–min flow control for multi-rate overlay multicast

We present a distributed algorithm to compute bandwidth max–min fair rates in an overlay multicast network supporting multi-rate data delivery. The proposed algorithm is scalable in that it does not require each logical link to maintain the saturation status of all sessions and virtual sessions traveling through it, stable in that it converges asymptotically to the desired equilibrium satisfying the minimum plus max–min fairness even in the presence of heterogeneous round-trip delays, and has explicit link buffer control in that the buffer occupancy of every bottlenecked link in the network asymptotically converges to the pre-defined value. The algorithm is based on PI (proportional integral) control in the feedback control theory and by appealing to the Nyquist stability criterion, a usable stability condition is derived in the presence of sources with heterogeneous round-trip delays. In addition, we propose an efficient feedback consolidation algorithm which is computationally simpler than its hard-synchronization based counterpart and eliminates unnecessary consolidation delay by preventing it from awaiting backward control packets that do not directly contribute to the session rate. Through simulations we further verify the analytical results and the performance of the proposed multi-rate multicast flow control scheme based on these two algorithms.