Optimization-Based Congestion Control for Multicast Communications

Widespread deployment of multicast depends critically on the existance of congestion control protocols that are provably fair to unicast traffic. In this work, we present an optimization-based congestion control mechanism for one-to-many communication with provable fairness properties. The optimization-based approach attempts to find an allocation of rates that maximizes the aggregate utility of the network. We show that the utility of multicast sessions must be defined in a particular way if a widely accepted property of aggregate utility is to hold. Our definition of session utility amounts to maximizing a weighted sum of simple utility functions, with weights determined by the number of receivers. The fairness properties of the optimal rate allocation depend both on the weights and form of utility function used. We show that although it is not strictly fair to unicast, the unfairness of our mechanism is bounded and can be controlled. Keywords—multicast, congestion control, pricing