What is Bittorent?
Bittorrent is a swarming downloading method which allows for large files to be distributed far quicker and more bandwidth efficiently than simply many users downloading from one server. When you use a torrent to download a file, you are also contributing to the files distribution. And you are able to download from many soures providing the file download, not just one mirror.
BitTorrent also allows for resuming a download, so if you have to stop downloading for any reason you can restart your client later and it will pick up where it left off and complete your download for you while it continues to seed what you aleady have.
As you receive sections of the file (which are individually verified) you will also start to send those sections of the file to other users who need them, similarly you will be receving the file from numerous other users. The more people who are attempting to download a file, the quicker it will spread. You can even shut the client down and restart it later (such as when you go to bed) and it will still seed the files that you have downloaded.
What does all of this have to do with Knoppix? Well Knoppix is large download (almost 4GB for the DVD version) and can have extremely large numbers of people looking to download it in a short space of time (when a major new version is released). Due to the load this places on the server hosting the download, Knoppix can be slow to get around onto the network of mirrors.
You will often see mention of people having problems with Knoppix where ultimately it comes down to a broken download. If you don't have the bandwidth to not care about having to redownload a copy of Knoppix if something goes funny, then Bittorrent is the answer. If Bittorrent is happy, you can be sure the file you have is identical to the original. For modem users who may have to reconnect many times to finish the download, this is a godsend (one crash could destroy the past 30 hours downloading by http/ftp, but bittorrent will fix the download without having to duplicate any significant amount of downloading).
Knoppix will be released via Bittorrent at http://torrent.unix-ag.uni-kl.de/
From there you may download the short .torrent-file for the wanted Knoppix version. After this open the .torrent-file with a Torrent client and start the download of the ISO. Per default "Transmission" is used as Torrent client within Knoppix. But you can also use "Bittornado Client" (bittornado-gui), "BitTorrent Download Client" (bittorrent-gui) or "KTorrent".
Now for the downside, in certain circumstances you just won't be able to use Bittorrent. If you are behind a router you do not control you will either not be able to use Bittorrent at all or your download speeds will be appalling (for example, downloading at the office). If you can control the router, then you should be able to open Bittorrent traffic to your computer and get maximimum download speeds.
Make sure that you have the ports 6881-6899 forwarded to your BitTorrent system in your router. Most current routers will recognize activity on a "trigger port" and automatically forward a range of ports to which ever local IP address they see activity of the trigger port coming from. This can be a handy way to forward ports to the computer that you use for BitTorrent. You can configure a router so that BitTorrent can be used on more than one system at the same time, but this involves more detailed port settings and is not useful for most home users. Also be sure that any software firewall passes this port range for BitTorrent.