Analysis of Multicast Clos Networks

Date of Submission: 
July 1, 1998
Report Number: 
This paper investigates three-stage Clos switching networks for multicast communications in terms of their blocking probabilities on a random traffic model. Even though lack of multicast capability in input stage switches requires a prohibitively large number of middle switches to provide compatible requests with nonblocking paths, the probabilistic model gives an observation that the blocking probability decreases drastically and then approaches to zero where the number of middle switches is far less than the theoretical bound. The S-shaped curves of blocking probability versus degree of fanout indicate that requests of high fanout are mostly blocked at some given referencenetwork utilization. A split routing algorithm and its blocking probability are introduced to enhance routability of the high fanout requests. We also corroborate the analytic model by performing network simulations based on random request generator and random routing strategy.