to code a program with a aproch method that he can find the optimal number of sdn controller in SDN network in c are we examine how well SOL’s results match original solutions, which are optimal (by definition). In all cases except ElasticTree, SOL finds the optimal solution. Due to complexity of ElasticTree’s optimization, SOL suffers a 10% optimality gap: the relative error in the objective value computed by SOL (i.e., relative to the true optimal objective value).