Joint optimization of primary and backup controller placement and availability link upgrade in SDN networks

In Software-Defined Networking (SDN), the control and data planes are decoupled, leading to a more programmable efficient network management. this paper, controller placement problem in SDN is addressed, jointly with of exploring high-availability tree subgraph, order support delay availability requirements between switches controllers. We consider that each switch connects primary backup controller. formulate joint optimization model as an integer linear programming (ILP), propose heuristic method when exact becomes impractical. Furthermore, we compare two ILP formulations, also redundancy solutions those considering path alone.