simulator choice depend on your purpose (case study: problem or application)
these most simulator for SDN:
1- MATLAB and Simulink
2- Pareto Optimal Controller Placement (POCO) Matlab-based tool
3- OpenDaylight SDN Controller with the Mininet Network Emulator
4- Mininet Network Emulator
5- NS-3 Network Simulator
6- Opensource Openflow network emulation (OFNet)
7- EstiNet 9.0 OpenFlow Network Simulator