RELIABILITY AND SCALABILITY OF DIFFERENT CONTROLLERS IN SOFTWARE DEFINED NETWORK
Software defined network (SDN) is a computer-based solution that, as a smart network manager, creates a single control plane to monitor the entire network system that only transmits data, rather than handling each system alone that is wasting time and effort. The transformation from physical network to SDN poses significant challenges which need to be deeply considered. Scalability and reliability are considered as important factor affecting the SDN network. In general, the reliability and scalability requirements are as follows: the chosen data rate during the transmission of information, the elimination of a single cause of failure, which increases the controller's availability, and finally, there are several topologies that enable scalable network architecture. Moreover, these requirements must be fulfilled within the SDN framework. We analyze in depth the structure of several controllers (i.e., hierarchical, scattered, and centralized). We examined controller failure program that improves SDN network flexibility and allows the infrastructure more robust and scalable.