My setup of having TP Link wireless router with PTCL Broadband modem was working fine. But I was getting bad internet on my mobile phones and PCs. If I bypass the wireless router and connect DSL modem directly, it start working fine.

So it seems issue is with wireless router. And I used to get error in my browser that DNS named not resolved.

Error 105 (net::ERR_NAME_NOT_RESOLVED): Unable to resolve the server’s DNS address.

The admin panel of my PTCL Broadband is on 192.168.1.1 and for TP-Link I set to 192.168.2.8. I replaced the primary and secondary PTCL DNS with Google Public DNS. And it works (Primary: 8.8.8.8 and Secondary 8.8.4.4).

Google Public DNS is a free, global Domain Name System resolution service, that we can use as an alternative to PTCL DNS. I am observing quality of Internet speed now.

You can also use OpenDNS addresses other than Google. Primary: 208.67.222.222 Secondary: 208.67.222.220. I will give try to OpenDNS too.