see what i know is that you need to appear for gate exam , which is held by some random iit every year . also you need to have more than 60 percent in your b tech. Get a good rank in gate and you get a call from iit for interview , if you pass it then you are admitted .Regarding the course structure mtech is of 2 years

You need to score above 60-65% in your B.Tech along with a great high score in your GATE entrance examination. Your percentile must be much higher. Please don't get confused between percentage and percentile. Even 99% percentile is lessee to get admission to IITs. You need even more and it's not that difficult to score if you study sincerely for your GATE examination as well as semesters of B.Tech.

M.Tech course is of 2 years.