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Why Does Speed Fluctuate So Much?


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My utorrent configuration should be okay because it has always worked fine. But recently downloads have stuck on about 1.5kB/s.

But they are not limited to this. The configuration still allows better speeds. There's occasional spikes to about 25kB and even a couple up above 30kB/s.

I'm with an outfit in Australia called Aanet and my broadband connection is ASDL at 512kbs down, my utorrent version is 1.6.1. I do a local speed test and get 51.26kB/s which is close enough to my theoretical max: 54kB/s, so it looks like it is not my line speed or any of the equipment involved with downloading files (the test downloads a 10meg file).

So it looks like utorrent. Here's some facts on the setup:

The file I'm downloading: Seeds 8(8)

Peers 5(163)

the logger screen is blank.

setup switches etc: No port randomisation

No UpnP

No Win Firewall exceptions (I don't use windows firewall I use firefox and I have a router on the small home LAN.)

Max uploads 9

Max download 0

Max connect 80

Max Peer per torrent 55

Uploads slots per torrent 3

DHT enabled

DHT for new torrents Yes.

Ask Tracker Yes

Enable Peer Yes

Protocol encryption for outgoing Yes.

Max active torrents (up or down) was 2, I just now changed it to 4

Max active down 2

Seed while ratio =<150

Seeding high priority - No

When at seeding goal rate to 1kB/s

I have downloaded a few files prior to this - maybe a total of twenty, no more, and I don't remember anything as slow as this. But recently things have been bad in other directions, too, the last three downloads I made were bad files, contained a virus or just wouldn't open.

Is this normal behaviour or is some wrong with my setup?

Or is utorrent itself under attack somehow?


ab :)

p.s. I just switched utorrent back on and it immediately gave me about 30kB/s but within a couple of minutes was down to 0.2kB/s

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You don't mention upload limit. 3 upload slots with 4 torrents means you should have > 20 KiBps upload... Also being on australian ISPs currently means you get throttled all to frell when you are connecting to international peers. On a recent set of torrents though I have proven I can pump up to 20 KiBps to a single peer on certain ISPs, the more likely scenario is you are choking / overloading the connection such that other peers do not want to connect to you and send data. Are you seeing alot of "S" flags under Peers tab?

Generally speaking, more concurrent peers == more overhead == less performance. Even on a 6 (well 2 MiBit line with p2p traffic) I only use max peers per torrent 20.

As to the fluctuation, it is possible you are connecting non-encrypted with peers that are on ISPs which send RST packets (basically man-in-the-middle spoofing packet attack where the ISP tells both parties to disconnect). You may need to force encryption and disallow legacy connections...

Also testing http://distribution.openoffice.org/p2p/ can verify whether you can obtain the same PEAK performance with p2p traffic (speed tests generally use HTTP, which is mostly unshaped/throttled/mangled).

If you are downloading bad files, you may want to re-think your content delivery medium... Perhaps switching to a different site or more thoroughly reading comments... BitTorrent relies on byte-for-byte copies, so if you got a virus from a file, it was in the original.

As to the topic title, speed fluctuates based upon the supply of the peers you are connected to. It is also limited by your firewalled state. Being firewalled means you have to rely on being able to connect to NON-firewalled or CORRECTLY-opened firewalled peers. With the same on your end, firewalled peers can connect to YOU.

Like I said check the Ooo torrent, if you get the same results it is definitely your ISP.

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"When at seeding goal rate to 1kB/s"

Seems awful low when you could just stop the torrent. At that speed, upload slots for that particular torrent should be reduced to 1 as well.

"Or is utorrent itself under attack somehow?"

It may be so in the sense that marginal hardware and software can overload and fail once you exceed their stable running values.

Have you changed any of µTorrent's advanced settings?

(Some settings changes can crash µTorrent and possibly even your computer as well!)

Have you tried Ultima's Troubleshooting Guide?:


Just like jewelisheaven, I suggest conservative settings to see if the slowdowns are less frequent.

Mainly your 4 total active+downloading torrents at once with 3 upload slots each is too high for only giving back 9 KiloBYTES/sec. Even at absolute, worst-case scenario, total upload slots should never exceed your upload speed in KiloBYTES/sec. µTorrent will even start reducing the number of upload slots it allows per torrent if you try, because it breaks compatibility with the BitTorrent protocol.

Have you tried disabling Resolve IPs, UPnP, Local Peer Discovery, and DHT?

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