Cost-delay path selection function for real-time multicast routing

A critical requirement for multi-party multimedia applications is to generate a multicast tree that has minimal overall network cost and acceptable end-to-end network delay in every path. These two features of the multicast tree are often conflicting in nature and the problem of minimizing the overall network cost in multicast routing is a Steiner tree problem which is known to be NP-complete. Most of the multicasting algorithms use heuristics that will optimize either the cost or the delay; however, the requirements of real-time multimedia applications cannot be satisfied. In this paper, a path selection function taking both the cost and the delay into consideration is proposed. A performance study is carried out by applying the path selection function to existing multicasting algorithms. Our results show that by simply changing the path selection function, the overall cost of the multicast tree can be reduced significantly while satisfying the real-time constraint of the multimedia applications.