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WTF: Upload speed drops when I set it to Unlimited


bugmenot

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Something I noticed with the latest version of μTorrent (1.8.3, build 15772):

When I set my upload limit to "Unlimited", the upload speed reliably and instantly drops to about 20 KB/s and stays there. When I manually set it to a value that exceeds my maximum upload speed, it uploads just fine.

utorrentupload1.th.png utorrentupload2.png

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  • 1 month later...

Hello,

some odditiy I noticed: When I don't limit my upload speed, µTorrent won't use the full potential of my connection.

I'm capable of pushing ~128 KB/s, but whenever I use "Unlimited", the upload rate instantly drops to about 50 KB/s. I thought maybe I was congesting my network, but no, when I set the limit to something higher than 128 it uploads just fine.

So, what is happening here? Is anyone else experiencing this?

Edit: Switeck, IT IS A BUGMENOT ACCOUNT. Rawr~ ;)

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Ok, assuming you've changed nothing in your advanced settings...

When you set upload speed to unlimited, uTorrent starts allowing far more upload slots at once.

(Yet for some reason the same doesn't happen when you have upload speed set too high...odd!)

If you have uTP peers/seeds connected to you, then upload speed may be unreliable due to uTorrent making very poor estimates of available max upload speed.

That probably confirms it's a uTorrent bug...but WHAT version of uTorrent is this?

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Alright, it's µTorrent 1.8.4, build 16150. There's plenty of uTP peers, and plenty of IPv6 peers (also IPv6 peers using uTP) when this issue occurs.

When I completely disable uTP (bt.transp_disposition = 5) and remove the upload limit, there's still some slowdown (~100 KB/s). Guess I'll blame that on the IPv6 peers. It's way faster than with uTP enabled though.

When I use the default settings (TCP + incoming uTP), I notice some slowdown after a while, probably when the first uTP peers connect.

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I would expect upload speed to be fastest WITH a set max limit AND no uTP or IPv6 peers.

If the upload speed tries to exceed what the ISP is giving you, the modem and/or ISP will be destroying random packets...perhaps even more than necessary...to keep you under max. If the packets destroyed happen to be needed to maintain speed (SYN/ACK packets), speeds plummet.

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I don't mean to hijack this thread but I'm having the exact opposite problem bugmenot is having. I wrote about this awhile ago but got zero answers. This only seems to happen when there's only 1 peer downloading the torrent. I can't upload at the upload limit I set it to, usually anything above 30Kb. The most I can upload to a single peer is 10-30Kb. But if I change the upload limit to unlimited it will begin uploading at my max limit, most of the time. If there's more than one peer downloading the torrent the speed will go up quickly. This happens whether I'm a seeder or superseeder. It didn't used to do this before but I can't figure out what changed.

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OK, but what exactly is happening here, and how can I avoid it?

I noticed that even with a set limit that I know my connection can handle, upload speed degrades over time, it just takes longer. For example, when I set the limit to 100 KB/s and come back two hours later, it's uploading at 80 KB/s.

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