Torrent traffic shaping?!?

Connection issues, drop outs or speed related faults for ADSL and ADSL2+ services

Torrent traffic shaping?!?

Postby sireddie on Mon Feb 13, 2012 7:04 pm

I'm not sure if this is a known issue, but lately I've been experiencing what seems to be torrent shaping.

During on-peak (a few minutes ago), when starting downloading content via the torrent protocol, the speed would slowly increase until it would max out my line speed, and then all of a sudden it would start slowing down until comming to a full stop.

5 sec interval:
Image

30 sec interval:
Image

After restarting uTorrent, 5 sec interval:
Image

Letting it run for about 30 min and it stabilizes at about 1/4 of my line speed, 30 sec intercal:
Image

I wouldn't care much during off-peak, but during peak when I need the download ASAP, this is quite anoying.

Could this be an issue with my torrent client (uTorrent) or would this indicate torrent traffic being shaped?

Suggestions welcome

Suggestions welcome.
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Re: Torrent traffic shaping?!?

Postby sireddie on Mon Feb 13, 2012 7:24 pm

And now they seem to have taken it down even further (to about 40kB/s):
Image
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Re: Torrent traffic shaping?!?

Postby Dazzled on Mon Feb 13, 2012 7:57 pm

I just finished one that maxed my line after about 20 connections came on board, quite quickly. From then on there was little speed variation. It eventually rose to 34. Have you looked at the peers individually? I used Deluge.


PS I have just tried with http://releases.ubuntu.com/11.10/ubuntu ... so.torrent, which is usually a good download speed test. It flew along for the first couple of hundred MB before I paused it, with little variation.
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Re: Torrent traffic shaping?!?

Postby shoner on Mon Feb 13, 2012 8:10 pm

sireddie wrote:I'm not sure if this is a known issue, but lately I've been experiencing what seems to be torrent shaping.

During on-peak (a few minutes ago), when starting downloading content via the torrent protocol, the speed would slowly increase until it would max out my line speed, and then all of a sudden it would start slowing down until comming to a full stop.

5 sec interval:
Image

30 sec interval:
Image

After restarting uTorrent, 5 sec interval:
Image

Letting it run for about 30 min and it stabilizes at about 1/4 of my line speed, 30 sec intercal:
Image

I wouldn't care much during off-peak, but during peak when I need the download ASAP, this is quite anoying.

Could this be an issue with my torrent client (uTorrent) or would this indicate torrent traffic being shaped?

Suggestions welcome

Suggestions welcome.


We do not shape any type of traffic. I would agree with Dazzled on checking individual peers.
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Re: Torrent traffic shaping?!?

Postby peteru on Tue Feb 21, 2012 2:58 pm

Your symptoms are indicative of a router with a limited NAT lookup table and a long(ish) TTL on expiring NAT entries.

For example, Billion 7402VGP routers can't handle more than ~1,500 NAT sessions and have a TCP timeout of 1800 seconds and UDP timeout of 120 seconds.

Something like an Asus RT-N16 will support about ~300,000 NAT sessions.

You may benefit from reducing the number of connections / peers allowed in your BT client.
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Re: Torrent traffic shaping?!?

Postby Dazzled on Tue Feb 21, 2012 3:27 pm

It's possible to run out of connections in the table, particularly if the router is old. Not so common now. On the telnet interface, poke around in /proc, typically the command cat /proc/sys/net/ipv4/ip_conntrack_max obtains the max number of connections available.

PS Some modem states can be monitored at /proc level from a computer, using perl, python, or expect scripts. There is an an example of monitoring (speed/SNR in this case) at viewtopic.php?f=284&t=38717&hilit=tones (second page)
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Re: Torrent traffic shaping?!?

Postby sireddie on Tue Feb 21, 2012 6:28 pm

Thanks for the suggestions guys.

I don't think that the router (Netgear WNDR3700) is the issue as it is about one year old. Also uTorrent is set for max 200 global connections and 50 peers per torrent. I was only downloading one torrent at the time.

If this happens again I'll make sure to try the torrent suggested earlier to rule out issues with peers dropping off all of a sudden.
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Re: Torrent traffic shaping?!?

Postby peteru on Tue Feb 21, 2012 9:56 pm

sireddie wrote:I don't think that the router (Netgear WNDR3700) is the issue as it is about one year old.

The age of the router is not necessarily a good indicator of it's capabilities. It tends to boil down to the firmware configuration and available memory. The 64MB of RAM on the Netgear isn't too bad, but the Asus has 128MB.

sireddie wrote:Also uTorrent is set for max 200 global connections and 50 peers per torrent. I was only downloading one torrent at the time.

Those numbers could easily result in a few thousand NAT sessions after a few minutes. Having DHT enabled will also drive the number of NAT sessions up. Because UDP NAT sessions can not be terminated until the timeout is reached, a 50 peer limit on the BT client does not mean a 50 session limit in NAT. If you connect or disconnect to a lot of peers and your NAT UDP session timeout is long, you will easily accumulate thousands of connections in just a few minutes.

Your best bet is to somehow figure out how to monitor the NAT sessions on your router. Failing that, drop the number of connections on your BT client right down. Something like 20 total and 10-20 per torrent. See if that helps (although you may have to wait for 5-10 minutes after you make the change, since the old sessions need to expire)
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Re: Torrent traffic shaping?!?

Postby peteru on Tue Feb 21, 2012 10:03 pm

Just looked it up and it looks like your Netgear router has a fixed limit of 4096 NAT sessions. There is no definitive information on the timeouts for various protocols, which will make a big difference to your BT config. Start with a small number of connections and then try increasing the limits until you start seeing a negative impact on the performance. Then back off a little, to give yourself some headroom.
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Re: Torrent traffic shaping?!?

Postby Dazzled on Wed Feb 22, 2012 5:20 pm

Peteru, I wasted some time checking out yoshac's code at http://wiki.openwrt.org/toh/netgear/telnet.console just to get into the Busybox shell to do a spot of monitoring. Now I know why I won't be buying one of these. Thanks for your info.
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Re: Torrent traffic shaping?!?

Postby samarium on Thu Feb 23, 2012 4:31 pm

Dazzled wrote:Peteru, I wasted some time checking out yoshac's code at http://wiki.openwrt.org/toh/netgear/telnet.console just to get into the Busybox shell to do a spot of monitoring. Now I know why I won't be buying one of these. Thanks for your info.


FYI, I have a 3800, and first thing I did after I verified it booted ok, was to flash openwrt on it. No hassles. Now I have a nice openwrt box again, much faster and with more storage than the old ASUS WL-500GP. I like the 3800.
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