I am often asked these questions, so I decided to write a summary of the answers.
So let’s start in order - here: https://shalaginov.com/2019/03/28/ngn-ims-sdn-nfv-triple-play-what-all-this-stuff-is-about-and-why-should-i-care/
Русская версия - здесь: https://shalaginov.com/2019/01/19/последовательность-и-различия-между-ngn