Thought for SDN development initiated from NGN history

The concept and architecture of SDN are similar with what of NGN in some aspects: From distributed controller migrated to concentrated one, the control layer is split from the media layer, the South Interface applies standardized control protocol and the North Interface is API for upper applications etc. But SDN and NGN difference are even more: Different industry background, Scenario, Open extend, protocols etc. But whatever, both of them are disruptive or innovative to the traditional network. Currently, the NGN deployment are closed to the end , but the SDN is raising rapidly. This article try to give some general analysis and comparison to these two technologies from aspects of industry background, scopes, architectures and applications, Initiating from NGN progress to SDN hot points. Through this comparison, the author hopes it can be helpful for those who have contributed a lot to NGN in past years to understand well SDN and prepare to transfer to SDN earlier.