You can try Mininet which very well supports SDN and NFV. It is an emulator instead of a simulator, so you can test real traffic on top of it. To know more about Mininet and SDN you can watch video lectures on you tube uploaded  by Prof.  Nick Feamster from  Princeton University. Additionally, you can check with ns3 network simulator  which facilitates the  simulation of networks consisting of open flow switches.   If simulating a very large network is your priority then ns3 would be a better option.

Thank You So Much For Your Useful Comments.

I also find these Videos in Github

https://github.com/mininet/mininet/wiki/Videos