Virtual concatenation-based elastic network embedding for inter-cloud-data-center networks

The elastic optical network (EON) provides fine-grained and orthogonal spectrum slots for the establishment of the elastic connection using orthogonal frequency division multiplexing (OFDM). Currently, the EON interconnection has realized the high-rate transmission among data centers (DCs). With the implementation of cloud DCs (CDCs) and EON virtualization, it becomes very essential to achieve the elastic network embedding (ENE) that facilitates the resource sharing in inter-cloud-data-center networks. The ENE operation consists of two components, the virtual-node mapping from virtual machine to CDC and the virtual-link (VL) mapping from virtual lightpath to fiber link(s). Thus an ENE request can be satisfied only when those two mapping processes have completed successfully. But during the VL mapping, some rigid constraints must be satisfied, such as the spectrum continuity, etc. This makes the ENE operation create the spectrum fragments over fiber links, which results in the denial of requests. Thus in this paper, we take the virtual concatenation (VC) into account when the VL mapping fails. The problem is formulated using the relaxed integer linear programming (ILP) model, and we also design a VC-based heuristic. Simulation results have verified the superiorities of the VC scheme on increasing the spectrum utilization and reducing the blocking rate of ENE requests.