Software Defined Network (SDN) is a concept based on a decoupling between the control plane and the data plane of a network. Thus, the network becomes programmable and can be adapted to the application requirements. The study that is discussed in this paper looks at load planning and load balancing in a SDN architecture where controllers are distributed. To do this, a model and theoretical methods for performance evaluation -with appropriate software tools to predict and control the quality of service offered to users- are exposed. This paper discribed also a distributed network architecture with SDN controllers and a module based on an adaptive load balancing algorithm that is fault tolerant and follows controller load. The experiments show a significant gain in efficiency of our solution.