oller adaption and migration decision (CAMD) balancing framework and a switch migration-based load balancing strategy have been proposed. This efficient switch migration technique improved the load balancing with reduced response time, and also it improved the end-users' QoS. In [118], an improved switch migration decision algorithm has been proposed for elephant flow or extremely large and continuous flow. By comparing it with CAMD, it is found to improve the SDN controller throughput, average response time, number of migration space, and the packet loss. In [119], a hierarchical two-phase algorithm was proposed. This algorithm integrated matching theory and coalitional games in order to achieve a near-optimal Nash equilibrium within tens of iterations. It reduced the total cost by 46% and achieved better load balancing among controllers in comparison to static assignment [120-122] In [120], a particle swarm optimization (PSO) and firefly controller population-based meta-heuristic algorithms have been investigated placement in order to achieve optimal placement of the SDN controllers. The results showed that the firefly algorithm performs better than PSO and random approach under multiple conditions. In [121], a framework for optimal controller placement with respect to different performance metrics was addressed by a heuristic approach. It is found to be less accurate but achieves rapid computation times. In [122], an algorithm based on hierarchical K-means was proposed to obtain more balanced controller placement [123] and Security In [123], a feedback-based scheduling scheme to determine the [124] appropriate encryption algorithm based on free-to-add mechanism has been proposed. Employing the feedback-based IPsec was found to improve the throughput and latency for the networks traffic that fluctuates significantly. In [124], extended support and defensive algorithm were proposed to make SDN OpenFlow communication more secure 1 A Comprehensive Study on 5G proposed in order to improve latency in smart city envi