A Heuristic Method for Controller Placement and Enhanced Availability between SDN Controllers

The Controller Placement Problem is an important and inherent component of SDN network design. Several QoS requirements such as delay and availability impose constraints on the controller placement in the network. The problem of guaranteeing `five-nines' availability between the controllers in a SDN network is addressed. We consider the problem of controller placement under delay constraints, while assuming a sub-graph of enhanced availability between the controllers. The sub-graph can be upgraded at a given cost, to achieve the desired availability requirements. To solve this problem, we propose a heuristic method to evaluate several controller node sets and the upgrade cost of the sub-graph for enhanced availability. The heuristic includes solving two optimization sub-problems, which are both NP-hard. The computational results show the trade-off between the number of controllers and upgrade cost and show that slightly increasing the number of controllers can lead to a significant reduction in the upgrade cost.