Peculiar network problem

[Bounty]

I'm trying to download Ubuntu via Bittorrent, which should be a half-hour job, but it's all kinda gone to shit in a very weird way.

I'm using Vista Home Premium, a WRT54GL router running Tomato 1.23 through a Linksys WUSB54GC connector, and µTorrent 1.83. My computer has a static IP with all relevant BT ports forwarded. The Windows firewall knows to allow µT both incoming and outgoing connections. µTorrent gets a green light, the connection works fine.

The problem is as follows:

Under normal circumstances I get about 400Kb/s. When I start a torrent, it *always* levels out at 60Kb/s, and the rest of my connection gets choked to hell. Browsing barely works, pages fail to load or take up to a minute to render properly (even simple ones with just basic HTML that otherwise load in a blink). Starting a second torrent slows the first one down until they're both at 60Kb/s. It's always that same number.

Using the same router and connection my last PC got consistent 300-350 speeds. It's not the torrent, it's not the router as far as I know, it's not the connection, all settings are correct, and I've basically reached the point where I'm out of tricks to try. What confuses me most is not the slowdown but the very peculiar combination of the torrent levelling out at precisely 60Kb/s while the rest of my connection goes to shit, and that this happens *only* with µTorrent running.

Ideas?

[rhoenix]

Your ISP is throttling torrent traffic.

[Bounty]

And they started doing this precisely in the week I bought a new PC, on a non-standard BT port? And this throttling drags the rest of the connection down with it? I very much doubt that.

[rhoenix]

I'm not going to give you a point-by-point rebuttal here. However, my hypothesis is falsifiable in the following ways:

1. reboot into Ubuntu on the same computer, and try downloading the same torrent file.
2. try another computer on the same connection, and try downloading again.

Please report your results. We will see from there.

[Bounty]

Ubuntu 9.04, Deluge 1.19, same hardware, same connection, same torrent: 300+ Kb/s, no browser issues. It's not traffic shaping.

[Bounty]

I doubt it's the driver since I do get 400Kb+ download speeds via the browser. It feels more like something along the line is overloading the router or hogging the connection.

[Resinence]

Ditch BT4luddites utorrent and try using the win32 version of deluge, since deluge apparently worked on linux.

[Beowulf]

Possibly you're running out of half open connections, and thus can't get as many seeds to download from? Don't really know what the solution is.

[rhoenix]

Alright, I withdraw my suspicions about traffic shaping or deep packet inspection. The only other thing I can think of which matches what experiences you've described might be either the network card driver for Vista, or the speed settings for it.

[Netko]

You are hogging your upload which chokes the "acknowledge" packets, thus slowing down your download because the remote source is waiting for them to send you the next packet.

Here's a link with a bit more info: http://www.cfos.de/traffic_shaping/traf ... ping_e.htm

Anyway, at the linked site you can buy a improved minidriver that prioritizes traffic at your computer so that acknowledgments are sent before html requests which are sent before torrent traffic and similar which is an effective remedy for the situation (I've been using their product for years).

Of course, the free alternative is to simply limit your upload in utorrent to around 80% of declared line speed which should give you enough breeding room for acknowledgments and browsing to work fine.

[Starglider]

which should give you enough breeding room for acknowledgments

You can breed ACK packets? Ah, so that's how denial of service attacks work, they're just factory farms for SYNs.

[Netko]

Yes, you see you have to have a good breeding program for them otherwise they never develop properly and are lazy and then you get problems like in the OP. True story.

I really shouldn't write posts when still groggy from a nap.

[Uraniun235]

Ditch BT4luddites utorrent and try using the win32 version of deluge, since deluge apparently worked on linux.

I looked at some screenshots of Deluge and it looks almost the same as utorrent; what's the big difference?

[Bounty]

My µTorrent upload speeds are properly set up. They're at 80% of my upload speed, and turning them down further changes nothing.

Ditch BT4luddites utorrent and try using the win32 version of deluge, since deluge apparently worked on linux.

I'd rather find the actual problem, thanks. I could just download everything from Linux but then I wouldn't learn anything.

Netko, thanks for the info; is that roughly the same as the QoS I have set up in Tomato?

[Netko]

Its pretty much the same thing, although details may differ, aside from the obvious different location of traffic shaping. This is weird, your description of the problem sounds like a typical acknowledge packet choking, but with your described configuration it shouldn't be happening.

Be sure to check if the prioritise ACK option is set in your Tomato QoS settings. Related to that, check to see the numbers of connections uTorrent is set to allow - dropping that down to 100 per torrent or even overall could be a good diagnostic attempt.

[Bounty]

Prioritize ACK is set.

I'm thinking the problem is either with Vista, the Vista driver for my wireless dongle, µTorrent, or a combination of those three. The fact that it works fine in Linux rules out the hardware, router settings and connection.

I tried bringing the connections back to 80 per-torrent and 80 overall but neither had an impact. µTorrent did work under XP with pretty much the same settings as it has under Vista right now.

[Uraniun235]

Try limiting the number of connections uTorrent is allowed to make. That should be somewhere in Preferences, I think.