A Layered Subtree Scheme for Multicast Communications in Large-Scale Elastic Translucent Optical Networks

To exploit the capacity introduced by elastic optical networks, efficient algorithms must be developed. Efficient modulation techniques have limited reach, so for distant destination nodes, the regeneration of a signal at a few intermediary nodes along the lightpath can effectively reduce the spectrum utilization and offset the extra cost, in terms of overall transceiver use, introduced by enabling the regeneration. In the context of multicast provisioning, although regeneration can be complex, it, in turn, due to its flexibility, further emphasizes the advantage of tree based routing over serving individual destinations. In this paper, we investigate the problem of routing, modulation level, spectrum allocation, and regenerator placement (RMSA-RP) for multicast provisioning, which, to the best of our knowledge, has not been previously addressed in the literature. Accordingly, we present a networking model through comprehensive integer linear programming, jointly enabling a routing method based on a subtree scheme as well as assigning a few nodes as regenerators of the signal. By means of an algorithm, we also propose a scalable framework to address RMSA-RP when the network is in operation. This algorithm implements a dynamic and automatic geographic partitioning of the destination nodes and then forms the corresponding subtree structures. Constraints taken into account include wavelength contiguity, wavelength continuity, and light splitting that affects the reach of the modulation techniques. Extensive simulation results show that the model can effectively support a greater number of demands without increasing transceiver use.