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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[quote comment="148414"]…If I pay a certain amount a month for a certain size pipe.. I want that amount of bandwidth available to me without filtering…
…I understand that Bandwidth costs money, so if thats the case, then ISP’s need to raise prices…[/quote]
Are you for real? So, you wouldn’t mind paying ten times what you’re currently paying so your ISP can afford to give you dedicated bandwidth?
What you don’t seem to realize is that the reason there is broadband is because companies rely on a “time share” method of dividing up their much much MUCH more expensive WAN connection costs. When you purchase broadband, you’re not purchasing an SLA’ed point-to-point pipe that’s dedicated to you; you’re purchasing a chance for equal use rights to someone else’s pipe. If you’re on cable, then you’re competing with everyone else on your node. If you’re on DSL, then you’re competing with everyone else on your DSLAM. If you’re on FiOS (BPON / GPON), then you’re competing with 32 other people on your splitter. And so on, and so forth.
If you really want 100% guaranteed access to a pipe / dedicated bandwidth, then you need to shop around for a T1, ether, microwave, or some other business class connection. Once you see the prices of these types of links, I guarantee you’ll appreciate your “best effort” broadband connection more.
- Tate
[quote comment="148414"]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)[/quote]
Sorry, I seemed to have missed this interesting tidbit. I’m going to go out on a limb and guess that you’re not in any kind of upper management position, but rather some level of technical support, right? Just curious.
Oh, and I’m not sure if you were implying otherwise, but if you were, I’d like to point out that telephone connections are still oversold to this day. Typical oversell ratios are from 1:3, all the way to 1:20 and beyond. There’s no justification from a financial or technical aspect to provision at a 1:1 ratio for the PSTN. To undersell and over-structure your company’s backend would be incredibly wasteful and moronic.
- Tate
Hey Comcast CEO Brian Robert: Why do you think people have broadband in the first place? Sheesh. Where do they find these luddites.
The next chapter in the Saga for Comcast will be Chapter 11.
“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.”
Fuck that shit! The ISPs are leaching us by billing $49 for shitty 3mbit service! Someone point this shit out in the the terms and agreements in the contract. “just because you pay $49 for a 1.5-3.0mbps connection doesn’t mean your entitled…”, my ass. If these fucking ISPs won’t give us comparable bandwidth to what other countries are enjoying for a third the cost, I’ll make sure to get my fucking money worth in service. It’s called getting what you pay for.
[quote comment="148441"]Someone point this shit out in the the terms and agreements in the contract. [/quote]
[quote]Examples of prohibited services and servers include, but are not limited to, e-mail, Web hosting, file sharing, and proxy services and servers[/quote]
Comcast TOS:
http://www.comcast.net/terms/use.jsp
They should sell Mb/sec and GB/hour combos. You’d pay more for 10MB/sec with 36000MB/hour than you would for 10MB/sec with 3600MB/hour. 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.
Heck, this would let them “give” even the low-end customers the highest burst speed possible while making those who generate a lot of traffic pay for it.
They also wouldn’t have to invest in protocol-specific traffic-shaping technology.
To address the needs of heavy downloaders, they can also have “peak” and “off-peak” rates, and offer “buy it when you need it” extra capacity. If I’m on the cheap plan, but want to watch a streaming video, I can buy 2 hours worth of full-speed access right now.
Many thanks for the iptables line. Router set and primed.
Who’d have thought I’d have to use the same trick against my ISP as Chinese users have to use to prevent cencorship?
The world is truly in a handbasket.
I’ve noticed this behavior for almost two months with Comcast. I check online sites that track ISPs who throttle bittorrent. Comcast was never on that list. It’s good to know the truth. The solution to keep your ratio up is to throttle your download until your upload reaches the desired level. Upload works fine until the download is fully completed.
My experience with Qwest DSL in the Portland, OR area: excellent for Bit Torrent. I can get 600-700 KB/s downloads and up to 100 KB/s uploads. Not quite the rates they advertise, but pretty close, and certainly no throttling. Comcast would be a bit cheaper for me, but it sounds like my seeding would be ruined.
Dang - I hate that Comcast is my only option, but it really is (other than dial-up). Technically there’s Qwest - but their speeds suck and they’ve actually publicly stated that they don’t plan on investing in fiber any time soon.
What is this iptable command line and where can it be configured in your router.
iptables -A INPUT -p tcp –dport $TORRENT_CLIENT_PORT –tcp-flags RST RST -j DROP
“I predict that within the next 2 months Comcast will loost 10% of its clients”
Exactly how is that going to happen? Broadband companies have a monopoly in their area of service. Do you think 10% of Comcast’s customers are going to ditch them for dial-up?!
“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.”
Thats because you’re retarded.
3 mbps = 3000 kbps = ~300 KB/Sec max
[quote comment="148484"]What is this iptable command line and where can it be configured in your router.
iptables -A INPUT -p tcp –dport $TORRENT_CLIENT_PORT –tcp-flags RST RST -j DROP[/quote]
This is a UNIX (Linux/BSB/etc) firewall rule. This blocks the reset packets Comcast is producing. It’s been years since I’ve used ipfw but I think this will work:
ipfw add drop tcp src-port (bittorrent_port) tcpflags rst
“iptables -A INPUT -p tcp –dport $TORRENT_CLIENT_PORT –tcp-flags RST RST -j DROP
is the solution, and soon torrent clients / peerguardian and alike hopefully implements it for windows aswell =)”
Is there any way to get this to work on a windows network through ICS with a server instead of a router??
Time to start complaining to the FCC and congress.
Ok…sorry everyone that’s posted on this and bitched about it…and I will say…before I state my thoughts and bias’s, that I (heart Digg…love the concept, needs to be tweaked…and it still doesn’t have an unbias’d vibe to it, it seams like everyone on the site is very open and atheist, and thinks that everything is ok and moral. Sorry guys, I’m not like that, I’m going to stick w/ my morals…N E Way…think of the ISP in this situation, they don’t want to get sued, and if they do, they’ll pass that bill right on to their customers. Bit-Torrent is notorious for illegal content, and until there is a standard protocol that LEGAL content is transfered on, they’ll keep blocking it. It’s simple ethics and business tacticks, don’t get screwed, cuz you’ll have to pass it on to your customer (or whoever’s below you in the business chain.)…that’s my thoughts…visit me on alex.sluiter.us (i know…it’s not fully up yet, I’ll get what i can on there asap) peace all…
The upload rate with comcast has never been super, they tended to focus on download rate over anything else. Personally I’m not seeing that much of a difference, my dl/ul rates even on semi-old torrents are still within tolerable limits.
Using Utorrent 1.6 (build 474) with outgoing packet encryption, port 80 for incoming connections, and the IP/Hostname reported to tracker is Google’s :D So that might have something to do with it.
“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”
LoL, I wonder when they will get pissed at TCP/IP then… :roll:
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