@Kenpachi Yes, this is an issue with this router. I too have the same issue. While i connect DLINK 2750U - Internet works just fine without any disconnection. The moment i connect 8961N, every few seconds it starts disconnecting. Infact i got the whole wiring from MTNL also replaced, still the issue persists. After so much of research and tweaking around i suspect this to be coz of "Echo Request Response" which needs to be set to 30. TP-LINK router doesnt have this setting, while the d-link has this setting. This setting is needed to get a response from ISP, if it doesnt get the response at the interval which is specified, it breaks. I suspect TP-LINK has internally defined this to be @ 5 and not 30, I still trying to check with support on this.

This hopefully should resolve the issue.