Résumé
This paper aims to introduce the hard optimization problem of determining tree-based explicit multicast routes with minimum cost. Explicit multicast routing has been proposed as a technique to solve the problem of multicast scalability in IP-based networks. Tree-based explicit routing is a special routing technique in which the multicast tree is encoded explicitly in the datagram headers. These enlarged headers may result in significant overhead traffic, so the cost minimization of this kind of routing is a relevant topic. This paper formulates the optimization of the communication cost per bit in tree-based explicit multicasting. If the multicast group is large, several trees are needed to provide routing for the entire group. It is demonstrated that the computation of the set of trees with minimum cost is an NP-difficult problem. The aim of the paper is the introduction of the bard optimization problem to find tree-based explicit multicast routes with minimum cost. The presented theoretical analysis is indispensable to find cost efficient routes for these kinds of multicast routing protocol.