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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Seems anti-competitive to me… Comcast sells internet access. They also sell video subscriptions, charging extra for on-demand and PPV movies.
If I’m paying to DL a movie from a legal subscription service that uses the bittorrent protocol, and it’s blocked, that’s anticompetitive behavior designed to get me to use Comcast’s services instead of the competitors.
Dorkbags. Grrr.
Tate: “45 Mbps DS3″ ?! the 90′is called and wanted there network design back. Currently networks are built using 10GE, 40Gbit POS in the core, Peering is done via GE or 10GE. Uplinking to costumes distributions switches is usaly done by GE. And if you are lucky enought to live in the developed part of he world, costumes are uplinked via Ethernet, FastEthernet, DSL* or Docsis*.
As customers, all we ask is to get what we pay for. Unfortunately, increasingly, ISPs reserve the right to throttle certain kinds of traffic in their “Terms of Service” agreements. One would hope that competition would come to the rescue, but countries like the US, through the FCC, tend to favor having only one or two providers in most markets with the resulting monopolistic consequences.
My own experience is with Qwest, the major and only real competitor in my local market to Comcast.
My first issue with Qwest was that my downloads were capped a 3Mb/sec, even though Qwest’s advertisements in the local paper and online trumpeted 5Mb/sec rates. Two calls to Qwest technical support resulted in statements that there was no technical reason for the cap, but I would need to call the business office to determine the reason for the cap. A two hour call to the Qwest business office didn’t provide a satisfactory reason for or removal of the cap. Currently Qwest advertises a 7Mb/sec download rate for DSL in my area.
My second issue with Qwest started early this year. Previously, torrent downloads had proceeded at the 3Mb/sec limit without problem. Starting this year, whenever the torrent download rate approaches 2 - 3 MB/sec, Qwest logs the PPPoE connection out.
While I believe that ISPs have the right to specify and enforce the terms on how their services are used, at least in the US, broadband customers don’t have the options available to shop for a better deal.
As customers, all we ask is to get what we pay for. Unfortunately, increasingly, ISPs reserve the right to throttle certain kinds of traffic in their “Terms of Service” agreements. One would hope that competition would come to the rescue, but countries like the US, through the FCC, tend to favor having only one or two providers in most markets with the resulting monopolistic consequences.
My own experience is with Qwest, the major and only real competitor in my local market to Comcast.
My first issue with Qwest was that my downloads were capped a 3Mb/sec, even though Qwest’s advertisements in the local paper and online trumpeted 5Mb/sec rates. Two calls to Qwest technical support resulted in statements that there was no technical reason for the cap, but I would need to call the business office. A two hour call to the Qwest business office didn’t provide a satisfactory reason for or removal of the cap. Currently Qwest advertises a 7Mb/sec download rate for DSL in my area.
My second issue with Qwest started early this year. Previously, torrent downloads had proceeded at the 3Mb/sec limit without problem. Starting this year, whenever the torrent download rate approaches 2 - 3 MB/sec, Qwest logs the PPPoE connection out.
While I believe that ISPs have the right to specify and enforce the terms on how their services are used, at least in the US, broadband customers don’t have the options available to shop for a better deal.
I predict that within the next 2 months Comcast will loost 10% of its clients
does anyone know the ipfw equivalent for the iptables command:
iptables -A INPUT -p tcp –dport $TORRENT_CLIENT_PORT –tcp-flags RST RST -j DROP
i’m running osx, and i’d like to give it a shot.
“CABEL CHANNELS SUCK . THEY SHOW THE SAME OLD CRAP.”
Too funny. This pretty much describes TV in general. This is not just a Comcast cable issue.
yep, i cancelled my comcast and just hop between verizon and earthlink customers in the vicinity. i just use it for ssh and svn so whatever - im not really raping their connection..
$65 a month and you cant even use bittorrent properly is ridiculous.
plus theres that joke ‘upstream boost’ that lasts for about 10 seconds, then drops back to 35-40K/second
its realy only the customers fault that comcast is able to raise prices all the time - too many people are willing to pay it
Um, question (a few in fact).
“Although BitTorrent protocol encryption seems to work against most forms of traffic shaping, it doesn’t help in this specific case.”
Then later:
“other users who find out that they are throttles[sic] might try BitTorrent encryption first, that seems to work quite well in most cases.”
Both “encryptions” link to the same page. How does this compute?
Also, I would like to know how Comcast can block BT traffic that is both encrypted and on a non-standard port.
How about that http seed feature in azureus? Surely they can’t block the 8080 port, or any other widely used one.
In New Zealand, the internet is getting worse and worse. They basically cap high usage users so that low-use users can browse their e-mails in 3MBPS glory.
Our plan went from unlimited downloads to…10GB cap. We get capped to 14.4K in the evening.
There are perfectly legitimate ways to rack up over 50GB of data a month - just intensively browsing streaming sites is a perfect way to get a hefty chunk of data. Then add in skype with video, some lossless itunes albums and itunes video, paid-for TV download, legal old movies which have expired copyright, trailers in HD, paid for applications, videography usage (uploading personal video files and downloading from other users), uploading and downloading high res photographs…(upload is counted with download in New Zealand so the cap = up and down)
In fact our ISP brags that you can download, oh my gosh, 1000 e-mails? Wow! And browse…20,000 websites? WOW! Amazing! Then why do you need 3Mbps internet? Wouldn’t 256 be more than sufficient?
[quote comment="148318"]“45 Mbps DS3″ ?! the 90′is called and wanted there network design back. Currently networks are built using 10GE, 40Gbit POS in the core,[/quote]
Maybe in major cities or if you are a major player, but not in middle America.
Many rural ISPs are still using DS3s or, horrors, bonded T1s.
There are many parts of the US where DS3s from the phone company are the only way to get transit unless you can afford to bury fiber or build a wireless backhaul chain to reach a major city.
Can ComCast folks switch to DSL Extreme? I have heard good things about them; why not give them a try?
Its tough to switch broadband ISPs in the USA because we have a monopoly system here (unlike with most of the world/even the developing world).
Some people may only have 1 DSL Option (say SBC At&T) and 1 Cable option(say Cox).
In Southern California they say we get ‘3mb/second’ or whatever but i have never gotten more than 256kb/second for a prolonged period of time.
Never ever more than 512kb/second.
The whole thing about 3mb/second I would like to know how they get that figure if no one gets it?
If they sell you “Internet access” intending to filter or otherwise interfere with your connections, that’s fraud. Hiding warnings about their intent in an agreement you’re unlikely to read is a deceptive practice. If you’re trying use your Internet access to share content with its creator’s permission, or to share your original work, and the access provider prevents you from doing it, then you have a right to taintkick them, legally speaking.
The problem is bad business practices (IE=overselling/overpromising)
They are doing the same thing now that they did in years past with the phone system. You paid a certain price each month for an analog phone line that is “dedicated” to you.. but the infrastructure was simply not there if everyone tried to be on the phone at once (what happens during an emergency or social upheaval). Thats just bad business. If you oversell, and under-structure your backend, you are a moron.
The problem of bandwidth saturation and download/upload heavy multi-media usage is NOT GOING AWAY. If anything its going to get worse for ISP’s. (and I do know what I’m talking about, I work for an ISP)
If I pay a certain amount a month for a certain size pipe.. I want that amount of bandwidth available to me without filtering. If the ISP isnt going to honor that, I’ll get a different ISP. You are an ISP, you arent the “digital file police”.. Your job is to provide bandwidth, not decide what bits are OK to send and which ones arent.
I understand that Bandwidth costs money, so if thats the case, then ISP’s need to raise prices, provide “tiered pricing”.. or “a la carte pricing” (your monthly bill is adjusted to reflect your usage, like gasoline or electricity).
just my 2c
I’m lucky to live in central maryland, we have fios competition with comcast. Comcast even tried to get our county to remove their rights to build saying they were here first. the county just slammed the door on their face and now we have fiber optics glory.
[quote comment="148372"][quote comment="148318"]“45 Mbps DS3″ ?! the 90′is called and wanted there network design back. Currently networks are built using 10GE, 40Gbit POS in the core,[/quote]
Maybe in major cities or if you are a major player, but not in middle America.
Many rural ISPs are still using DS3s or, horrors, bonded T1s.
There are many parts of the US where DS3s from the phone company are the only way to get transit unless you can afford to bury fiber or build a wireless backhaul chain to reach a major city.[/quote]
You beat me to the punch TiAMO, though I couldn’t have said it better myself. Until the world has ubiquitous OC-768 backbones in every city, small ISP’s have to take what they can get in terms of their WAN peers.
- Tate
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