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
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Confirmation of Rogers Canada traffic shaping:
http://iqdupont.com/blog/?page_id=19
Canada has so little ISP competition that they can traffic shape, admit it, and still get away with it.
[quote comment="149194"][quote comment="149035"]> Can any of you give me some
> pointers on where to enter this
> using DD-WRT on a Linksys router?
Do not bother. It does not work unless both sides of all (or at least most) of your peer connections also block RST-flagged packets.[/quote]
ummm that is not correct as far as I can tell since comcast is only doing this to their customers on their network. So all the other peers world wide not on comcast are not facing this issue so this will let you connect to them and stay connected.[/quote]
I did the original testing that found this issue (see the link at the bottom of the TF article) and I did try that test, specifically ( see http://www.dslreports.com/forum/r18726009- ), but if you have findings to the contrary — that’s great! Please double-check and confirm. Like I said in the above post, it does seem to keep the connection from dropping, but then it becomes clear that no bytes are moving on that connection.
The quoting of the above comment got all screwed up, but you get the idea: my testing shows the linux ‘iptables’ trick ultimately fails.
For everyone using Windows XP:
I wrote a guide for Comcast users on how to test whether, and how much, you are being affected by this problem.
Please visit this page http://www.dslreports.com/forum/r18901881-#18901881
The page explains how to test for it manually, and also gives you a Windows XP batch file that can automate the testing.
“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.”
Well… gee… If I pay $50 for 1.5-3mbps… shouldn’t that be exactly what I get? If your network can’t handle it, it sounds like it is time to upgrade, or to not charge such high prices for a service that you can’t fully provide.
Ernesto is correct. The only real way to get around this problem is with a VPN or ssh (where you’d run a command-line bittorrent client).
Messing around with your firewall rules isn’t going to help much. The server still gets sent an RST packet as if it came from your client and Comcast can still kill the connection in other ways.
Best to sign up with a service like https://vpnout.com
Then you don’t have to worry about traffic shaping, cut connections, your ISP spying on you, or getting legal notices from aggressive cartels.
-Riskable
http://riskable.com
“I have a license to kill -9″
so I had a conversation with comcast which went like this: do you use a router? do you have a firewall running? do you use antivirus? do you have port filtering? is it a public tracker? did you try a different port? Could there be things installed you don’t know about (in my mind: WTF?)
Their excuse “This is an unsupported issue” my response: “if you’re reducing speeds on downloads thats a comcast issue”
response: it’s not comcast there could be a software issue with the bittorrent program.
I have the audio recording of the entire conversation, so please let me know if you’d like it. I recorded it for quality assurance purposes, as comcast explicitly allows by calling them.
everyone needs to just bombard comcast like the nuts for jerico thing =)
http://www.nutsonline.com/jericho
i would be interested in hearing that audio recording of your call with comcast. i’m sure digg would love it too.
[quote comment="148283"]
If you sell a 3Mbits line, then you need to be sure, it can handle 3Mbits when everybody is using 3Mbits. They oversell like hell. Overselling = profits. And if people use to much bandwidth, then lets just throttle whatever application they are using.
[/quote]
I guess the all the net provider bastards took one from the POTS folks. Reason why you cannot place a call when everyone else is trying during a large event / disaster? The POTS system is built only to handle one out of about four to 15 customers using a line at once. I guess that is the reason for all the false advertising in broadband, and everyone couldn’t have 3MBs at once.
I dont mind if I cant upload because my ratio got fucked whilst using original bittorrent at demonoid by I cant even download, my internet just drops.
There is too much money for this problem to get solve in a ‘fair’ manner in the US. While the public play for network neutrality plays out, the real players prep for the eventuality that the curtain will fall and that the FCC theater will have no real bearing on reality. Hearing hte situation in Canada is disheartening as well.
My personal opinion is that we as individuals need to look at setting up our own wifi networks using the same tech being considered to create brandband networks where there is no infrastructure. (http://www.techdirt.com/articles/20070329/113707.shtml)
I tried in utorrent 1.6.1, setting the Protocol Encryption: OUTGOING, as FORCED. And i noticed that a brazilian ip is downloading one of my linux isos. And the connection hasn’t interrupted its been about 10 minutes straight. Maybe they are not able to knock down fully encrypted connections? If this is the solution, or part of it, i hope in the next utorrent releases and azureus releases the clients come with forced or enabled encryption as default.
“Funny. Then don’t oversell the lines.
…
If you sell a 3Mbits line, then you need to be sure, it can handle 3Mbits when everybody is using 3Mbits. They oversell like hell. Overselling = profits.”
Overselling = Better prices for users. If they were to makes sure a line could handle everyone using max bandwith all at once like you suggest, you would literally be paying 5-6x as much. You’re the type of person that would bitch and moan about that also. People like you can never be satisfied. If you want what you’re suggesting, buy a T1 line. Too expensive? Then shut the fuck up.
[quote comment="148304"]Use Hamachi to establish giant secure virtual lans on the internet. Its free, cheap, easy.
I personally have the “bogomip” network with a private password using the Hamachi servers. I use that for my personal home to work VPN, took maybe 5 minutes to set up and get working.
If torrent sites would use hamachis P2P encrypted VPN techniques to make a large virtual lan exist, they could privately host their own websites on private networks - outside of the public eye.[/quote]
This is what that nullsoft guy was talking about when he made waste before he quit. Your right. Large private encrypted networks are the way to go.
I’m on Comcast in San Francisco. Three or so weeks ago my upload went to near 0/kbs. Now I know why. I use BitTorrent rarely, but it’s an important application to transfer large graphics files between workgroups. I understand the ISP’s grief over a few users using an outsized amount of bandwidth, but why not just cap total transfers?
Yes, I’m one of those affected now.
Two different torrent sites for bootlegs are now affected. Y and TTD.
Chattanooga, TN.
GRRRR! at least there are still dc++ hubs.
First of a few issues with some of the posts people are making. You all know that when you pay for 6mb or 8mb or however fast your service is rated for that it is in megabits not megabytes so your only really gonna get ~500-800k/s MAX not 6mb/s as some of you seem to think.
That said I don’t mind if I can’t have true unlimited bandwidth BUT and this is a big but, then DONT ADVERTISE AS UNLMITED. I would be ok if they said your cap is 200gb a month and then your throttled. They don’t though. They proudly announce unlimited so thats what I expect. Dont give me this BS about then go with a dedicated T1 line. Yeah i know thats dedicated bandwidth. The point is they are using deceptive advertising practices.
Would I switch isp’s over this? Sometimes I wish I could unfortunately Comcast is the defacto monopoly here. It’s comcast or dialup.
RCN used to throttle but now they dont. Try RCN. I had to dump Comcast too earlier this year.
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