Controller placement problem in software defined networks

<span>The requirements <span>for the network are increasing by expanding and spreading Internet. The Previous techniques of do not meet modern needs, thus, a new technical presents software-defined networking (SDN). SDN recognizes as promising model that separates control plane (traffic routing topology) from data (network architecture layers). has some features find in single controller or many controllers instance programmable, flexible, scalable. In current SDN, multiple essential. Therefore, optimal number their locations is most significant challenge, known placement problem (CPP). It deploys within while meeting presentations considered conflicting nature example: credibility, load balancing, latency, energy efficiency, computation time. Many studies researched ways to develop solutions for improving scalability, place selection SDN. This paper CPP gives comprehensive review issues based on recent well-known research extract available solution strategies. Finally, it discusses limitations future study directions can support researchers this field.</span></span>