SDN, if properly cooked, can help with many challenges in cumbersome legacy networking, but where should we start?
There is little value in getting an SDN controller. SDN is NOT just about controllers, it's a complex ecosystem: programmable components embedded in hardware, many tools available as open source or hardened by innovative suppliers, alternative solutions usually exist for one challenge. How can we understand, what really brings value and what is just using buzz around SDN, but nothing more than a rebranded legacy product priced unfairly?
Does SDN definition bring any clarity? Let's try.
Software-defined networking (SDN) is an approach to computer networking that allows network administrators to manage network services through abstraction of higher-level functionality. This is done by decoupling the system that makes decisions about where traffic is sent (the control plane) from the underlying systems that forward traffic to the selected destination (the data plane).
From https://en.wikipedia.org/wiki/Software-defined_networking
This definition might be meaningful for a technical person. However, it does not show how SDN brings value.