Engineering

No. Its no at all compulsory. But if you are thinking to do Masters in India, then GATE. Is the best. Even if you spend a year in preparation, no problem, go for GATE. With out GATE.
1. Career aspect: First thing you can't get into well reputed institutes like IITs, NITs, and some government colleges. When you done with you are M.Tech, the college from where you have done your Masters is very important. It matters a lot in initial stages of your career. Most of the private colleges in India for name sake they are providing M.Tech degrees, but they don't have required lab facilities and well qualified faculty too, so what is the use obtaining degree from such universities?
2. Financial aspect:You have take care all financial needs by yourself. If you have cleared GATE. You will be getting stipend of 12400 pm, that too in government institutes you will have very less fees. Do you know? IIT Kharagpur tuition fee is 5k per semester, including everything ie food+Hostel+internet+medical etc. It comes out 33k per semester. You won't get such low fees in anywhere in India. Actually any GATE. Qualified, if he takes admission through GATE. In any AICTE approved colleges should stipend of 12400 pm, but it never happened in reality. You know its all government, no need to explain our system.