Control plane innovations to realize dynamic formulation of multicast sessions in inter-DC software-defined elastic optical networks

It is known that to support the applications such as datacenter backup and migration, multicast should be supported efficiently in inter-datacenter (inter-DC) networks to carry the corresponding point-to-multiple-point communications. Moreover, due to the traffic dynamics in inter-DC networks, we might have to consider the case that the multicast members can join or leave a multicast session dynamically. Therefore, in this work, we try to leverage control plane innovations to realize dynamic formulation of multicast sessions in inter-DC software-defined elastic optical networks (SD-EONs), which are equipped with multicast-incapable bandwidth-variable wavelength selective switches (MI-BV-WSS'). Here, one key issue to address is that the continuous changing of multicast group members can degrade the optimality of a multicast-tree. Hence, we propose to rearrange the multicast-trees adaptively to reduce their spectrum usage. Meanwhile, we try to minimize the frequency of rearrangements to avoid unnecessary operation complexity. Based on these considerations, we propose several multicast-tree rearrangement algorithms for updating multicast sessions dynamically with lightpath reroutings in inter-DC SD-EONs. Both partial and full multicast-tree rearrangements are studied. Simulation results indicate that the proposed algorithms can rearrange the multicast-trees intelligently such that the blocking probability can be reduced effectively with the least lightpath reroutings. Next, based on these theoretical investigations, we consider how to implement the proposed algorithms in the control plane of an inter-DC SD-EON. We extend the OpenFlow (OF) protocol to support the dynamic formulation of multicast sessions and also design the functional models in the control plane elements to realize multicast-tree rearrangements. Experiment results verify the effectiveness of our proposed algorithms and system design.