Comcast Throttles BitTorrent Traffic, Seeding Impossible
Written by Ernesto on August 17, 2007Over the past weeks more and more Comcast users started to notice that their BitTorrent transfers were cut off. Most users report a significant decrease in download speeds, and even worse, they are unable to seed their downloads. A nightmare for people who want to keep up a positive ratio at private trackers and for the speed of BitTorrent transfers in general.
ISPs have been throttling BitTorrent traffic for almost two years now. Most ISPs simply limit the available bandwidth for BitTorrent traffic, but Comcast takes it one step further, and prevents their customers from seeding. And Comcast is not alone in this, Canadian ISPs Cogeco and Rogers use similar methods on a smaller scale.
Unfortunately, these more aggressive throttling methods can’t be circumvented by simply enabling encryption in your BitTorrent client. It is reported that Comcast is using an application from Sandvine to throttle BitTorrent traffic. Sandvine breaks every (seed) connection with new peers after a few seconds if it’s not a Comcast user. This makes it virtually impossible to seed a file, especially in small swarms without any Comcast users. Some users report that they can still connect to a few peers, but most of the Comcast customers see a significant drop in their upload speed.
The throttling works like this: A few seconds after you connect to someone in the swarm the Sandvine application sends a peer reset message (RST flag) and the upload immediately stops. Most vulnerable are users in a relatively small swarm where you only have a couple of peers you can upload the file to. Only seeding seems to be prevented, most users are able to upload to others while the download is still going, but once the download is finished, the upload speed drops to 0. Some users also report a significant drop in their download speeds, but this seems to be less widespread. Worse on private trackers, likely that this is because of the smaller swarm size
Although BitTorrent protocol encryption seems to work against most forms of traffic shaping, it doesn’t help in this specific case. Setting up a secure connection through VPN or over SSH seems to be the only solution. More info about how to setup BitTorrent over SSH can be found here.
Last year we had a discussion whether traffic shaping is good or bad, and ISPs made it pretty clear that they do not like P2P applications like BitTorrent. One of the ISPs that joined our discussions said: “The fact is, P2P is (from my point of view) a plague - a cancer, that will consume all the bandwidth that I can provide. It’s an insatiable appetite.”, and another one stated: “P2P applications can cripple a network, they’re like leaches. Just because you pay 49.99 for a 1.5-3.0mbps connection doesn’t mean your entitled to use whatever protocols you wish on your ISP’s network without them provisioning it to make the network experience good for all users involved.”
Customers on the other hand like to fully use their connection, and don’t agree that traffic shaping is the correct solution. One reader commented: “If you pay for an internet connection, that’s what you should get from your ISP — an internet connection. Not a connection that will let you browse the web and check email, but little else. If an ISP has issues with the amount of data a customer is transferring, then the ISP needs to address that issue with that customer, and not restrict every user in one class of traffic.”
I guess this battle will go on for a while and I would advise Comcast users to try setting up a VPN connection to get around the traffic shaping, other users who find out that they are throttles might try BitTorrent encryption first, that seems to work quite well in most cases.
More details about the Sandvine application can be found here.
Previously: BitTorrent Anime Downloaders Identified, $3500 Bill in the Mail
Next: TorrentPod Episode 43
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Here is a method that worked for [i]me[/i] to get around this seemingly-impenetrable barricade. I had created a free shell account and was using an HTTP proxy in combination with encryption. My client (rtorrent) doesn’t support SOCKS, so I tried to socksify the application, but I couldn’t get that to work and I was only able to upload on one torrent with all the others unable to connect to the tracker.
The user at http://forum.utorrent.com/viewtopic.php?pid=269426#p269426 provided an excellent suggestion that just so happened to work for me. I was fairly certain it would not.
Just set the port range to 40,000-50,000 or any other sufficiently high range. I’m uploading at max speeds now!
I’m still using encryption but it may well work just the same without it.
I hope this comment helps out other people. I sure am happy to have finally resolved this issue.
I don’t think Comcast has a right to do this, mainly because there are many companies that use torrents as a main source of data distribution. Debian is an example of this.
The central point here is that the broadband business is incredibly uncompetitive in the U.S. Where I live, I can choose between Qwest DSL and Comcast cable. Qwest’s service is shitty and I can’t even get the high-speed package where I live.
And now Comcast is fucking with my bittorrent uploads. What am I supposed to do? As a consumer, I have no recourse.
I don’t understand why, but as an earlier post said changing the dns to something other than Comcast’s seems to fix it for me. Very strange
I can understand the saturation issues Comcast is facing. Yet I can also understand the fact that many companies utilize BT for their products as do I to distribute my work (photographer).
To uniformly blanket the entire network with their throttling methods is not only wrong, it should be illegal.
P2P is not illegal. BitTorrent is not illegal. What they need to do is focus on individuals who use the most bandwidth and address the issue on an individual basis.
Many people, myself included, use the BT network for completely legal reasons and now since we are not able to, feel as if Comcast is breaching their own TOS by not providing us the services which we are paying money for.
I am now looking into Bellsouth DSL, the only other broadband provider in my area. The speeds are not as fast as Comcast, but at least they actually let their users upload.
[quote comment="148281"]I am as of today the 17th of August a Comcast cable internet subscriber. I’m not sure if this is affecting all Comcast or possibly untrue, but I am currently downloading/seeding without any issues. I seed on timer where day,early evening hours i upload at 32kb/s and late evening early morning at 64 kb/s and have done so for almost 2 years on a 24/7 basis with no problems from Comcast for doing so. I’ve up’d over 500 Terabytes this year so far, and that’s just in bitorrent traffic. I still use my net connection for games and surfing/email as well on top of this. I live in a smaller area so this may be the reason we aren’t affected. I can’t say anything bad about Comcast as of this time period. I had issues with sprint/earthlink dsl and their crap speeds before this but comcast has been reliable and almost always higher than rated speeds.[/quote]
You are full of cr@p. 64kbps*60*60*24*239 = 1.3tb
At thats IF you don’t throttle to 32kbps. So you were over exagerating by 500times. You are close but haven’t even reached the monthly transfer that most people get cut off with.
this stinks im at college now and the dorms have a cutt off rate at 2gb up/down a week and the only other option is to get comcast and now that i have comcast i cant even use it for what i want to use it for my upload is next to nothing after leaving any torrent program run for an hour verison fios is the way to go for any one who can switch
cry me a f-cking river ISPs. You charge for a service and I f-cking intend to USE WHAT I F-CKING PAY FOR.
Oh so you just want me to send you a payment everymonth and not use your service. wouldn’t that be just peachy for you?
This sh|t is almost as bad as verizonwireless
[quote comment="148454"]If you exceed your quota, you are sent to a “fast enough to browse the web and read email” “penalty box” until your last-60-minute usage drops below your quota.
[/quote]
I work for a UK ISP listed as a bad ISP by Azureus, but this is exactly how our throttling works, only usage is measured in 240 minute increments and reset when it drops below. I can tell you ISPs do oversell and if it were up to me, I’d have customers pay for bandwidth rather than shape those who might legitimately need it. Heavy torrentors sucking up resources who are willing to buy the bandwidth would be paying a fair amount for their use, allowing infrastructure upgrades to handle them. It’s not trivial to do such upgrades but I feel it’s necessary with ever increasing high bandwidth content,
I’d say our throttling scheme is fair, unlike Comcast’s, but I think ISPs in general are setting themselves up for a bandwidth crisis if they keep going this direction, as throttling can only go so far before even the e-mail users get unhappy and demand is not decreasing,
btw, that RST flag you Comcast users are dealing with is just shitty policy, I encourage everyone even outside of Comcast to do this(trivial for helping your fellow Comcast peers), which applies it to all ports.
# iptables -A INPUT -p tcp -m tcp –tcp-flags RST RST -j DROP
This is better as it will stop incoming RST to all ports, since not all connections are established on your listening port. The problem is that Sandvine sends one to the user and one to the server(aka your peer). So this could work nicely if the peer blocks them too. Get the word out, The ISP I worked for looked at Sandvine and I studied it as they did so, but thankfully the wigs here found it an unethical and user-imposing tool, unlike their ad propaganda would have many believe.
Perhaps the solution is to have those of you capable of effective programming and with a distinct knowledge of this difficulty, program against it and produce a Defender P2P Net from a location where you are more likely to be free from attack–as in Sierra Leon (considering an intelligent person would actually live there)
This could be a server designed to feed the world for a minor price, say $2.00 a month, which would support not only the system, but positive growth.
Whoever wrote this article is smoking crack. Comcast uses Sandvine for deep packet traffic analysis. I am a Comcast customer and my torrents are seeding and leaching great. Get the facts before you post shit like this dude.
can some1 tell me the command that i am supposed to use in ubuntu…because when i type the command above in the terminal it doesnt work
Bandwidth-consumption arguments are total BS propaganda — this is about KILLING BITTORRENT by murdering the torrents, pure and simple.
If it was about bandwidth, they wouldn’t let millions of people browse YouTube for hours on end, as opposed to the much, much smaller pool of people who P2P over bittorrent.
could someone explain where i put the iptable command under the tomato firmware? Is it under scripts? Thanks.
I personally contacted my ISP in regards to throttles I could see being set on my file sharing activities. Their response was to review their policy page.
I really don’t like where this is headed and I had a friend who had the same problems, but when he connected to his works VPN account there was no problems.
So I got a VPN account at the same place :) http://www.strongvpn.com
They say its Gigabit speed but I don’t know how I can tell, I’m not that fast on my home connection. But when I’m on it.. it’s no problem for my P2P activities.
It’s $15 a month though, is there anything cheaper out there?
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