In reply to Ravi Patil.

Hi Ravi - yes it is a bit :-) [this kind of write up!]

Let's debate :-) I don't see "lower cost" as a use case. Sure it's a good and worthy business objective, but is it a use case? network path failure is a good example of a use case.

Good question whether and how SDN solves such issues. If we separate out some of the variants of SDN .....
(1) As I understand, OpenFlow v1.0 did not have controller resilience built in to the spec (I could be wrong here on the details but I do recollect at least one pretty major resiliency feature was not there in the 1.0 spec). Of course this is being addressed as versions come out however OpenFlow still IMHO has to be proven in large scale enterprise and SP networks under the variety of use cases that customers require (for example I'd argue that the well published Google use cases [search as main use case] don't need to address the wide variety of challenges we see in many networks today).

(2) Cisco ONE Platform Kit API. This is an API to existing network equipment and features - so you have all your existing resiliency feature, proven, if you follow this route!

(3) Virtual Overlays - again time will tell if these networks have all the resiliency features required. I will write a blog soon on some of the troubleshooting challenges in these networks - this will show you that some virtual networks have resiliency challenges today!

Thanks again for the question, good questions, happy to debate (and apologies for delay in replying, due to the holiday period)