What is Software Defined Networking (SDN) and how is it going to change Networking in future?

SDN is present now a days also.We are still using software defined networks as you know IOS are actually the software which we install on hardware to deploy our networks.

SDN just change the way we are doing things.Now all devices have their own control plane(like stp,vtp,dtp etc).With SDN control plane will be centralized on controllers. Instead of configuring each and every device in the network, we will be having a controllers called APIC(Application programmable infrastructure controllers) , on which we configure policies and push those policies to all the devices in the network and all devices will act accordingly.

APIC is feature available with Nexus 9k.