Thanks for help but the problem was automatically resolved 2 days back. It was bsnl problem.
I'm facing the same problem here. But I read it somewhere that this problem has something to do with TP-Link devices. I'm able to play Youtube videos on my lappy (chrome/firefox ; RJ45 - W8968) but not on my android phone (wifi W8968). And the strange fact is that when I change my modem to Netgear DGN1000 Youtube videos on my phone play like before.
BTW I use BSNL DNS.
I tried changing DNS setting on my phone in advanced options in wifi setting but internet ceased to work on my phone after that.