Online replacement of distributed controllers in software defined networks

To deploy Software Defined Networks (SDN) in large-scale datacenters, distributed controllers need to be used to achieve scalability and reliability. In such kind of continuously running systems, maintenance often involves online replacement of specified nodes in distributed controllers to upgrade their hardware/software, while the service interruption of controllers and processing errors are not allowed. In addition, load-balancing needs to be re-considered since the hardware of controllers may become heterogeneous due to the replacement. To address this problem, this paper proposes ORDIC, an Online Replacement method of DIstributed SDN Controller in a disruption-free manner. ORDIC enables the safe disruption-free replacement of a specified controller while ensuring network switches utilize resources of the new controller efficiently. In this paper, we build the prototype system on Floodlight to demonstrate our design and test the performance. The experimental results show that: during the replacement process, ORDIC can efficiently allocate appropriate loads to the new controller, so as to improve the overall performance of the distributed controller platform.