Optimal multicast routing: modeling and discussion

Routing is an important issue in multicast and has great influence on system performance and network resource usage. To make maximum use of the network resources, the total cost in the system should be minimized, this corresponds to the optimal multicast routing (OMR) problem. Until now, there has been little work done on the modeling and theoretical analysis of this problem. The purpose of this paper is to present a theoretical framework for the OMR problem. A system-optimal multicast routing (SOMR) model is proposed and several conclusions are derived from this model, which give an insight into the OMR problem: 1) in the presence of block effect, the OMR problem has a unique link flow solution, 2) the optimal multicast routing is achieved only if the traffics are distributed on the minimal first derivative cost (MFDC) trees, and 3) even if the minimal tree (the Steiner tree) is built for each group, it usually doesn't mean the optimal solution.