An Approximate Algorithm of Controller Configuration in Multi-domain SDN Architecture

Software Defined Networking (SDN), which de-couples the control plane from the data plane and assembles the control ability of switches to a centralized controller, has drawn great attention recently and shown lots of merits. In large networks, however, if only one omniscient SDN controller is deployed, there will be high capacity demand and long delay due to the significant amount of control information, which are harmful to the networks scalability and reliability. Intuitively, some researchers have proposed to divide the whole networks into multiple domains and try to cooperatively manage the networks by using a group of controllers, none of which is able to monitor the complex networks alone due to capacity constraints, but they do not provide a method to configure the networks efficiently. In this paper, we try to figure out the least number of controllers we need in the above circumstance and address how to configure the network with multiple-domain controllers. For this NP-hard problem, instead of reaching an optimal algorithm, we propose an approximate algorithm called Greedy Sub-Graph Cover Problem algorithm (GSGCP) in a simplified but equivalent multi-domain control model, in which each domain is abstracted to a single node. Simulation results verify that the proposed algorithm configures the networks with an acceptable performance and computation complexity for any given network topology.