SLT ADSL, DNS and Daemontools
Many users of SLT ADSL complain about the connections slowing down to a crawl and even timeouts when browsing. I also ran into the same situation and tracked it down to a problem with Sri Lanka Telecom's DNS servers.
Two of their servers '184.108.40.206' and '220.127.116.11' sometimes stop responding completely and you cannot even ping them. The solution then is to use an external DNS server. Many of the other ISP in Sri Lanka have forgotten to block ports on the DNS servers and virtually anyone can use their DNS servers.
You shouldn't be suprised by this lack of attention to details, quite often you see so called sysadmins from Sri Lankan ISPs/Telecos asking elementary questions in mailing lists.
A more sophisticated solution than using a third party DNS server is to set up your own. daemontools obviously would be the first choice. When setting up however, I ran into a small problem.