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uTorrent cyclically spikes above uploadlimit, causes massive latency


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When I set an upload limit in uTorrent, it seems to use it more as an average goal than a hard limit. uTorrent's upload speed will drop to way below the limit, shoot up way past the limit (as if trying to average it out), slowly drop to the limit, and then drops precipitously once again.

The problem with this is that while I generally keep my limit at 40 or 50KB/s, and my upload capacity is about 80KB/s, these spikes saturate my connection and cause enormous latency (+300-500ms).

Here are two screenshots illustrating the problem. You can see that it is a well defined pattern, exactly what shape the graph takes. The screenshots are from build 474, but the problem also occurs in beta build 483 (the speed graph in 483 is identical). The first screenshot is with 5 second granularity, the second is with 1 second (you can see me dropping speed cap from 50 to 40 in the first one)



As far as I can tell, uTorrent has always done this, and it has happened on three different computers on two different internet connections/routers (two laptops, one desktop, one DSL line and one cable line). So it shouldn't be connection or computer specific.

Is there some advanced setting that might fix this?

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  • 4 weeks later...

I have the same exact issue, and I have played with my Upload slots over the course of the past year with no noticeable difference whatsoever. Have ranged from five to 20, currently on 15.

The only time that my upload stays solid, is when I am not actually downloading that specific torrent and am in Seed only mode, it is really weird to say the least.

I currently have two torrents running while in Seed only, one( public tracker ) in Forced Start, maximum of 1kB up with down speeds ranging from 2kB-15kB. The other( private tracker ) just in Start mode uploading at ~56-57kB, unlimited up with a global up limit of 58kB and obviously not downloading anything.

If I start downloading the private tracker torrent, my upload speed starts doing exactly like in this pictures.

This has been going on since µTorrent came out, surprised it hasn't been nailed down yet. I think it is an issue with actually setting individual torrent limits, cause that's what seems to bring this problem out for me. But who knows!


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Yes, i think there is such a issue with certain settings/systems. I got a friend who had this problem since 1.4, no matter what he did to the settings the problem persists. after he removed his router, problem solved.

And yet, we got like 20 friends who used to same router and settings setup and there wasnt any problems. (A ISP gave out free routers for contracts recently so tons of ppl got them)

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Using only 1 KB/sec upload speed max with anything other than 1 upload slot MAX for that torrent is definitely hostile settings. Your download speeds will almost certainly be very bursty and probably won't go over 15 KB/sec...certainly not sustained over 10 KB/sec.

If your connection is trying to maintain over 50 global connections at once, then that's a possible problem with some marginal networking software or hardware...such as a Belkin router or Surfboard modem...or Zone Alarm software firewall.

Half open connections max set in µTorrent's advanced settings does not need to be set over 8 for anything short of 10 megabits/sec upload+download bandwidth...and may need to be lowered to 4 if ANY problems are experienced!

Running with too many or too few upload slots can cause all kinds of bursty activity. There needs to be no more than 1 upload slot PER 1 KB/sec of upload speed...preferably 1 upload slot per 3-10 KB/sec of upload bandwidth. Having more than 10 KB/sec upload speed per upload slot will just mean you're uploading faster to people than you're likely to download back from them...because they probably CAN'T upload that fast back!

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I meant default settings except the limit! (how can I talk about the upload limit without setting it?)

the problem is just like it was said - there are peaks that are far beyond the limit which make download slower(peak in upload=fall in download).

I think it's trying to maintain the avg upload speed at all cause

here are the other settings I've changed(which are minor):

upload slots for each torrent = 4

dowload speed=0

upload speed = 6

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