Routing Multicast Streams in Clos Networks

Multicast routing in high speed networks is one of the key issues in the design and implementation of applications such as video conferencing. Traditionally, the problems are formalized as either the shortest path problem or Steiner tree problem where the objective function is either the shortest path or the minimum costs associated with the path. In this paper, we study an on-line multicast routing problem in Clos network with minimizing internal blocking ratio. We propose three families of heuristics: Least busy (LB), First t (FF), and Minimal bandwidth (MB). Our simulation shows LB and FF families perform well with unicast streams, but they are not good enough to deal with multicast streams. The MB family has signiicant performance on multicast streams. The MB family can be reduced to set covering problem which is well known NP-complete problem. We also propose heuristic minimal bandwidth (HMB) family which are derived from greedy set covering algorithm to trade oo computing time and routing performance. These algorithms perform almost as good as the expensive MB family and as simple as FF family. Therefore, the HMB is the best algorithms we proposed for multicast routing.