In order to simplify the management of the traditional network, software-defined networking
(SDN) has been proposed as a promising paradigm shift that decouples control plane and
data plane, providing programmability to configure the network. With the deployment and the
applications of SDN, researchers have found that the controller placement directly affects
network performance in SDN. In this paper, the state of the art of controller placement
problem is surveyed from the perspective of optimization objective. First, we introduce the …

Software Defined Network (SDN) is an emerging network paradigm which provides a
centralized view of the network by decoupling the network control plane from the data plane.
This strategy of maintaining a global view of the network optimizes resource management.
However, the implementation of SDN using a single physical controller lead to issues of
scalability and robustness. A physically distributed but logically centralized SDN controller
architecture promises to resolve both these issues. Distributed SDN along with its benefits …