Cross-control: A scalable multi-topology fault restoration mechanism using logically centralized controllers

Logically centralized network control design enables data-plane and control-plane separation in communication networks. Until today, traditional fault restoration mechanisms based on such designs were restricted to `one´ centralized network manager to detect faults and manually reroute traffic around effected areas. Nonetheless, this design is challenged by the overall scalability, restoration latency and convergence delay of the physically centralized controller. As a result, in this paper we argue that one can do a far more efficient network design. Here we propose, model, and design the problem of placing multiple centralized controllers, among multiple network topologies, so as to maximize the resilience and scalability of such networks- within the bounds of convergence delay. We begin with formal model definitions to optimize the controller placement locations. Based on the model, new ILP formulations have been defined. Subsequently, a simple but efficient greedy based heuristics has been proposed to solve the ILP. Performances are quantitatively evaluated and our results show significant reliability improvements in a given topology.