Serving multicast requests on single-layer and multilayer flexgrid networks

Advanced services require a high bitrate, e.g., multigigabit, multicast connectivity being provided by core transport networks. Multicast services can be supported either by one single tree connecting the source to every destination of the multicast request or by a set of paths. The tree scheme could reduce resource utilization, and as a result of the bitrate that might be required, providing them directly on the optical layer could bring benefits. Apart from those benefits, with the advent of flexgrid technology, connections with 100 and 400 Gbits/s and beyond can be set up, which opens up opportunities to create virtual topologies on which multicast services can be provided. The kind of transponders that are needed under the single-layer and multilayer approaches are slightly different. While bandwidth-variable optical transponders (BVTs) can be used in the multilayer approach, assuming that the virtual topology is supported on high-bitrate optical connections so as to facilitate the performance of grooming, using sliceable BVTs (SBVTs) in the single-layer approach might help to share capacity in the transponders. In this paper, we compare the performance of high-bitrate multicast services using the path and the tree scheme on the single-layer and multilayer approaches. Mathematical programming models for the tree scheme on the two approaches considered are developed to compute the routing for incoming multicast requests in dynamic scenarios. With the goal of reducing computation time, heuristic algorithms providing a much better trade-off between optimally and complexity are proposed. Exhaustive simulation results carried out on three national core network topologies show that the tree scheme on the multilayer approach outperforms the rest of the options.