Load balanced multicast with multi-tree groups

Given a fixed network infrastructure, i.e. a set of multicast sources and their corresponding receivers, we investigate the problem of constructing multicast sessions that maximize network utilization for all sources involved, under a fairness constraint. This is done by ensuring that multicast session construction protocols uniformly distribute multicast traffic over all links. In most standard IP multicast protocols (e.g., PIM), a single multicast tree is constructed for each multicast session and all data packets corresponding to a session are multicast on the same tree. A key observation in this paper is that distributing multicast traffic for a session over multiple multicast trees can dramatically increase the load balance and improve network utilization. In fact, our simulations indicate that merely using a few multicast trees per session can improve the common throughput of all sessions by a factor of up to two. We devise a standard compliant, distributed protocol which we call load balanced and cooperative multicast or LBCM to efficiently construct multiple multicast trees for each multicast group. We show how LBCM may be implemented on top of standard multicast protocols to improve network utilization in currently deployed systems.