Bittorrent is a peer-to-peer system that is designed for rapid file distribution. The key to bittorrent is its use of segmentation. When a file is shared on bittorrent it is divided up into many "pieces". Users who are downloading the file receive these pieces off other users who are solely uploading. Downloaders also exchange the pieces they have with other downloaders. Essentially, bittorrent utilises the available upload bandwidth of the downloaders as well as the sole uploaders. The concept of bittorrent is better explained on the official web site, here.
The official bittorrent client does not allow capping of the upload speed. This is because the key to bittorrent is users pooling the maximum amount of upload bandwidth (as mentioned above). This slows all downloads to crawl. As a result, I have made a modded version of the official client. However, bare in mind that bittorrent is biased towards users with more upstream bandwidth. If you decide to severely cap your upload speed, your download(s) on bittorrent will slow down also. There are two versions of the mod, one for 512/128 ADSL users and one for 256/64 and 128/64 ADSL users. The latest version of the mod can be downloaded below. As you can appreciate, these mods come with no support or warranty of any kind. The mods are based on the original bittorrent client which was written by Bram Cohen.
| Mod Version | Mod Download Link |
| 512/128 Mod | part 1 , part 2 , part 3 |
| 256/64 Mod | part 1 , part 2 , part 3 |