SDN Controller Placement in LEO Satellite Networks Based on Dynamic Topology

Software-defined networking (SDN) logically separates the control and data-forward planes, which opens the way to a more flexible configuration and management for low-Earth orbit satellite networks. A significant challenge in SDN is the controller placement problem (CPP). Due to the characteristics such as the dynamic network topology and limited bandwidth, CPP is quite complex in satellite networks. In this paper, we propose a static placement with dynamic assignment (SPDA) method without high bandwidth assumption, and formulate CPP into a mixed integer programming model. The dynamic topology is taken into account by effectively dividing time snapshots. Real satellite constellations are adopted to evaluate the performance of our controller placement solution. The results show that SPDA outperforms existing methods and can reduce the switch-controller latency in both average and worst cases.