Distributed delay constrained multicast path setup algorithm for high speed networks

The problem of finding an optimal multicast tree in a point to point network translates to the Steiner problem in graphs. Since the Steiner problem is NP complete, heuristic approaches are required for path setup. The problem takes a new dimension in wide area networks, where centralized algorithms are not feasible, and distributed schemes are needed. It is also desirable that node participation for path setup is limited to nodes directly involved in the multicast. An additional requirement that comes from the nature of the applications such as video conferencing that use the multicast support from the network is that of bounded end to end delays along any path from the source to each destination in the multicast tree. We present a heuristic algorithm that ensures delay bounds, is distributed and produces trees that are only slightly more expensive than those produced by centralized algorithms. Further we examine the degradation in performance in case of changing delays along network links (where QoS guarantees on delay are not available), and propose ways of making the tree adaptive to these changes. This dynamic routing approach minimizes resource reservation demands and also makes changing multicast groups permissible.