Since last few days I was getting disconnects from 70% of the games but battle.net connection was fine. Recently my brother changed MTU setting from my router (D-Link 502T) to 1452. Which probably was the reason I was getting frequent disconnects.
I restored factory settings so that MTU default value is 1400 now. I have played about 10 games and it didn't disconnect from any games.
Also I changed my network cards MTU to 1500 with TCPOptimizer(optimal settings). I am not sure changing either router or LAN MTU setting did the trick. This can be added to user tips maybe?