Solving The Backup Controller Placement Problem In SDN Under Simultaneous Targeted Attacks

Targeted attacks on software defined networks (SDN) can heavily disrupt the network connectivity and thus service continuity. One of the worst disruptions occurs when a targeted attack on network nodes is able to divide the network into different components (islands). Since the network is usually managed by a limited number of controllers, such attacks can result in isolating a significant proportion of nodes from the surviving controllers, causing major disruptions in service availability. In the paper we study the issue of adding a number of additional controllers to the network in order to increase its resilience to targeted attacks. For that we introduce an original optimization model for solving the related controller placement problem, based on a novel measure of network service availability called average network resilience (ANR). Additionally, we analyse two strategies to generate simultaneous targeted attack scenarios used in the numerical study illustrating the model effectiveness.