Résumé
Connection based networking is a basic technology for data transmission in Transparent Optical Networks (TON). In this kind of networks, important elements of the network design and management are related to the routing decisions in the optical level. To diminish the use of resources, multicasting is required for a lot of applications. Usually, multicast routes are light-trees in TONs. These trees should satisfy the known optical constraints. If it is not possible by a unique tree, “light-forests” are proposed. An alternative and more ergonomic solution called “light-hierarchy” was proposed to solve the multicast routing in constrained cases. We present this non-elementary structure and discuss the advantages and the difficulties of its computation. A related issue is the protection of multicast routes. Mainly segment-based and cycle-based protection schemes are proposed to protect routes against link and eventually node failures. The protection of branching nodes in multicast routes is more difficult. The route should re-established for all successors of the failed branching node and the optical constraints should be satisfied after the re-routing. To improve the protection, we also present non-elementary protection schemes for multicast routes. The aim of the propositions is to eliminate unnecessary constraints in route computations.