The cable that used by
slt called SEA-ME-WE 4 (South East Asia-Middle East-West Europe 4)
http://en.wikipedia.org/wiki/SEA-ME-WE_4
has only a bandwidth of with a total capacity of 1.28 Tbit/s...
and that bandwidth from London is shared between telecommunications between Singapore, Malaysia, Thailand, Bangladesh, India, Sri Lanka, Pakistan, United Arab Emirates, Saudi Arabia, Sudan, Egypt, Italy, Tunisia, Algeria and France. as Weekipedia says.. this is shared between Mobitel and also Dialog..
Well Lankabell Has There Own Cable cost of US $ 27 million and a 3billion investment
http://www.lankanewspapers.com/news/2008/6/29165.html
and there cable is connected to the FLAG Cable System which is connected directly to 50countrys.. and Even USA and also linked to AT&T cables.. and this cable has a connection speed of 1.20 Tbit/s to Srilanka through the Lankabell network
http://en.wikipedia.org/wiki/Fiber-Optic_Link_Around_the_Globe
+ there are also light cables which is used for dialog + lankacom airtel etc which is slower. .. wel if you are thinking of a good ISP lankabell is the fastest in SL