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This question has been asked numerous times on the web and the given answer almost always is yes. However, I never saw any support and I suspect that the answer is given purely to give the motivation for people to seed.

I am not aware of any automatic fairness system that takes place over the torrent protocol. It is probably possible for users to block others who they deem to be not generous enough, but does the torrent network already discriminate against people who set low limits for upload?

It's clearly the case that an unrestricted maximum upload speed can hamper download speeds and most of the time it is recommended that one set the limit at 80%-90% of the capacity, but this question deals with setting the upload speed too low, not too high.

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5 Answers 5

up vote 5 down vote accepted

There is a sort of fairness system - BitTorrent uses a choking algorithm to handle congestion and prevent this kind of thing. I don't know exactly how it works, but it ensures that connections to users who upload more are prioritized. If your client does not receive any piece of the file from a particular peer, the peer may be snubbed.

More information.

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+1 - This is the correct answer. See superuser.com/questions/669222/… for excerpts from official publications. –  Andrew Cheong Nov 4 '13 at 16:22

Using uTorrent on 2014 Macbook Air.

When my uploads are limited to 1kbps, my download speed is almost always 100kbps or lower.

When I removed upload limits, my download speed immediately increased to 2.5mbps

It would appear that in my case, upload speed absolutely affects download speed.

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My understanding of the justification is that if you do not allow adequate upload bandwidth your bittorrent client to freely upload data your restricting your ability to upload information to the seeders your connected to as to the current state of the transfer and to further request new information.

I personally have not sat down and studied this nor do I have a reliable source handy but the theory behind it is solid as you can't have download without upload.

If you have time sit down with wire shark and compare the frequency of uploads to seeds comparing high allowance to uploads and low allowance to uploads

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I've recently been thinking about this as well. A quick test of a download I was engaged in with µTorrent gave me these results.

Limited to 1 kbps upload gave: 10 - 50 kbps download.

With the download still running I change to this.

Unlimited upload speed gave: 4 - 8 mgps download.

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I can say that in my experience this is not the case. I have tested with various upload speeds to see if it would affect my download speeds. In any case the only issues I have found would be having the upload speed too high. As you mentioned this does hamper download speeds.

I have my upload speed set to the lowest possible level when doing downloads but I share when I am not around my PC.

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