Two-layer optimization of survivable overlay multicasting in elastic optical networks

Elastic optical network (EON) architectures are considered as a very promising approach for future optical transport networks, since they efficiently use the spectrum resources and provide high bandwidth scalability and granularity. At the same time, the multicast transmission technique is widely used to provide increasingly popular streaming services in computer networks. In this paper, we focus on optimization of lightpath connections in EONs supporting bandwidth-demanding multicast-capable applications. Since multicasting in the optical layer is still not deployed in most of real-world backbone networks, we propose to provision the application-layer multicasting in an overlay network. To this end, we study a two-layer optimization problem that combines the optimization of multicasting in the overlay network (application layer) and the optimization of lightpaths in the EON. What is more, we address our problem with the survivability assumptions and we propose several survivability scenarios that can be applied in the network (in both the overlay network and the optical layer) to provide the required protection against failures. In the overlay network, we propose to protect the data stream by a dual homing scheme, wherein in the optical layer, we apply a dedicated path protection scheme. Moreover, in both layers we consider a scenario with no protection. We perform numerical experiments to compare different protection scenarios and to evaluate potential benefits of using multicasting instead of a typical unicast transmission. We use several comparison criteria (metrics) that affect the considered elastic optical network, namely, network deployment cost, power consumption and spectrum usage. The obtained results show that the values of these metrics significantly depend on the applied protection scenario. Eventually, we can see that multicasting brings significant savings in terms of all defined metrics when compared to unicast transmission.