Har _lånat_ denna text, jag har ej skrivit den själv:
The download speed mostly depends on the seeder-to-leecher ratio (SLR). Poor download speed is mainly a problem with new and very popular torrents where the SLR is low.
(Proselytising sidenote: make sure you remember that you did not enjoy the low speed. Seed so that others will not endure the same.)
There are a couple of things that you can try on your end to improve your speed:
Do not immediately jump on new torrents
In particular, do not do it if you have a slow connection. The best speeds will be found around the half-life of a torrent, when the SLR will be at its highest. (The downside is that you will not be able to seed so much. It's up to you to balance the pros and cons of this.)
Limit your upload speed
The upload speed affects the download speed in essentially two ways:
* Bittorrent peers tend to favour those other peers that upload to them. This means that if A and B are leeching the same torrent and A is sending data to B at high speed then B will try to reciprocate. So due to this effect high upload speeds lead to high download speeds.
* Due to the way TCP works, when A is downloading something from B it has to keep telling B that it received the data sent to him. (These are called acknowledgements - ACKs -, a sort of "got it!" messages). If A fails to do this then B will stop sending data and wait. If A is uploading at full speed there may be no bandwidth left for the ACKs and they will be delayed. So due to this effect excessively high upload speeds lead to low download speeds.
The full effect is a combination of the two. The upload should be kept as high as possible while allowing the ACKs to get through without delay. A good thumb rule is keeping the upload at about 80% of the theoretical upload speed. You will have to fine tune yours to find out what works best for you. (Remember that keeping the upload high has the additional benefit of helping with your ratio.)
If you are running more than one instance of a client it is the overall upload speed that you must take into account. Some clients (e.g. Azureus) limit global upload speed, others (e.g. Shad0w's) do it on a per torrent basis. Know your client. The same applies if you are using your connection for anything else (e.g. browsing or ftp), always think of the overall upload speed.
Limit the number of simultaneous connections
Some operating systems (like Windows 9x) do not deal well with a large number of connections, and may even crash. Also some home routers (particularly when running NAT and/or firewall with stateful inspection services) tend to become slow or crash when having to deal with too many connections. There are no fixed values for this, you may try 60 or 100 and experiment with the value. Note that these numbers are additive, if you have two instances of a client running the numbers add up.
Limit the number of simultaneous uploads
Isn't this the same as above? No. Connections limit the number of peers your client is talking to and/or downloading from. Uploads limit the number of peers your client is actually uploading to. The ideal number is typically much lower than the number of connections, and highly dependent on your (physical) connection.
Just give it some time
As explained above peers favour other peers that upload to them. When you start leeching a new torrent you have nothing to offer to other peers and they will tend to ignore you. This makes the starts slow, in particular if, by change, the peers you are connected to include few or no seeders. The download speed should increase as soon as you have some pieces to share.
Why is my browsing so slow while leeching?
Your download speed is always finite. If you are a peer in a fast torrent it will almost certainly saturate your download bandwidth, and your browsing will suffer. At the moment there is no client that allows you to limit the download speed, only the upload. You will have to use a third-party solution, such as NetLimiter.
Browsing was used just as an example, the same would apply to gaming, IMing, etc...
