A list of Internet service providers (ISPs) that are known to cause trouble for BitTorrent clients or P2P in general and the reason why are listed here.
One of the biggest problems are providers that that perform traffic shaping on P2P protocols, see avoid traffic shaping
on how to counter that. You'll need that if your ISP is listed with an encryption level greater than 0 or a question mark on the Bad ISP list.
Hopefully your ISP will not have an encryption level other than 0. Use that list to see if your ISP does anything to throttle Bittorrent speeds.
Cablevision's Optimum Online, for example, prevents seeding on Bittorrent. Seeding is the uploading of torrent data to other people. Seeding is essential, because people with higher seeding speeds are more likely to have faster download (leech) speeds since more peers (other computers) are likely to connect and mutually transfer torrent data. Therefore, people using Optimum Online will have slower download speeds in Bittorrent.
Luckily, there is something you can do. Azureus recommends to try enabling Tools -> Options -> Transfer -> Use lazy bitfield or try encryption otherwise
.
