Dynamic Upgrade to SDN from a Global Perspective: Model and Its Heuristic Solutions.

Software Defined Network (SDN) has been considered as one of the most promising next-generation network solutions due to its network programmability. However, the upgrade from legacy IP network to pure SDN network is in general a gradual process. From a global perspective, a dynamic upgrade strategy should not only aim to pursue the local goal at each step, but also strive to optimize the final global solution when the upgrading process terminates. This raises three essential questions: which switches to upgrade, when to upgrade, and how to deploy controllers. Due to the interaction between the local goals at intermediate steps and the global goal at the final step, answering these questions altogether from a global perspective is challenging. In this paper, we study the dynamic SDN upgrade problem from a global perspective and answer these three questions altogether. We formulate the problem as a dynamic optimization problem that optimizes the global and local goals at the same time. We then propose two new formulations to combine the global and local goals, and two heuristic algorithms to solve them, respectively. We evaluate the proposed model and algorithms on realistic network topologies. The results show their feasibility and superiority.