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Comcast implements new throttling system [U]

updated 06:15 pm EST, Thu November 5, 2009

Comcast two-tier throttling now active

(Update clarifying timing) Comcast in a new FCC notice (PDF) revealed that it has already begun implementing a new throttling system. The approach is now service-agnostic and will lower the priority of any data packets if a user's cable modem either tops 70 percent of download or upload bandwidth for more than 15 minutes or else is flagged as bogging down the CMTS node, which manages a neighborhood's cable modem traffic.

When throttling is active, local routers will either reduce the priority of the connection altogether for 15 minutes or until average bandwidth use falls below 50 percent during a similar span. The throttling could lead to packet loss in "extreme" cases where enough priority information exists to flood out that data, Comcast says. Certain traffic won't be completely throttled, however, as a node facing little to no congestion will send low-priority traffic through at a similar rate to normal data.

The update fulfills a promise made by the company to drop format-specific throttling following an FCC ruling that barred it from discriminating against BitTorrent and other specific protocols. The decision followed the establishment of a non-binding net neutrality principle and the eventual discovery that Comcast had masked its behavior by publicly denying its throttling even as tests confirmed the practice. Moves are underway at the FCC to formally ban such earlier tactics but likely won't take effect until 2010 at the earliest. [via The Inquirer]

Update: Although the FCC filing is new and provided significant added detail regarding the throttling method, the system reflects what was implemented in late 2008.

by MacNN Staff



  1. Mr. Strat

    Joined: Dec 1969


    Comcast sucks

    This should be popular with Slingbox owners. Glad I kicked Comcast out of my house years ago.

  1. LGgeek

    Joined: Dec 1969


    will be looking at AT&T uverse

    I have already noticed this and will be looking at AT&T. If all of the isp's do this then I'm not going to continue to pay for high speed access. I can have low speed download my mail while I get cup of coffee. If they are going to charge me for high speed access then I expect to get it or lower my bill to reflect the lower quality product I am now getting.

    I wonder how much it cost Comcast to "influence" the FCC.

  1. Arty50

    Joined: Dec 1969



    I thought I was paying for 100% of the bandwith 24/7. Not 70% in 15 minute increments. I sense a class action suit over this...

  1. lamewing

    Joined: Dec 1969


    Already switched

    I switched from Comcast to ATT Uverse and never looked back. I agree LGgeek. If other companies start to follow suit I will simply use the internet at my university as well as at Barnes and Noble and Panera.

  1. Telekinesis

    Joined: Dec 1969


    What a scam.

    They start off throttling off P2P as their evil scapegoat to complete what they are now doing - throttling *all* traffic indiscriminately.

  1. Zaren

    Joined: Dec 1969


    My Comcast died tonight

    I get Internet and phone service from Comcast, and both were down for six hours tonight. The paranoid me wonders if tonight's outage was due to this new throttling. I just cancelled my cable TV service this week after switching over to Dish Network. I guess it's time to sign up for UVerse now.

  1. nowwhatareyoulookingat

    Joined: Dec 1969


    you can only get the rated speed

    from Comcast for a few seconds at a time. Maybe their ads should be forced to reflect this?

  1. b9robot

    Joined: Dec 1969


    I thought being a provider meant providing somethi

    So I thought being an internet provider meant that you would provide the bandwidth that you claim for more than 15 minutes.

    I'm glad I don't use such a lame service as Comcast. They claim the best speeds but what an oxymoron. You can't use those speeds they claim. Anyone on Comcast I think you should email and call them and tell them if they throttle your service you will throttle them out of your house!
    They sucked as a cable TV provider with half channels and snow outs 50% of the time and now they suck at providing internet service.

  1. danviento

    Joined: Dec 1969


    Punishing Legit Use

    So when you're downloading that Mac OS 250MB update or some movie from the iTunes store or a bunch of back TV episodes from iTMS (which total in the GBs), you'll see your speed drop? Seriously?

    There's a reason people pay the extra $10-$30 a month for higher speed access- they want to be able to drastically shorten download times for the somewhat irregular use of legitimate services like these. To disable such abilities defeats the purpose of paying for higher bandwidth.

    Call it false advertising. Call it a retraction. Call it a dumb business practice.

    Call it what it is: a provider that sold more bandwidth than they actually have, more than they actually can support. It's treading on the line of being a ponzi scheme.

  1. TheSnarkmeister

    Joined: Dec 1969


    Very clever of them, but too late...

    To bad Comcast was not sufficiently clever to have thought of this even sooner. If average users had been being throttled back every time had they tried tried to use their NetFlix accounts, which is what is going to happen now, this aspect of Network Neutrality (now rechristened "Open Internet" in Newspeak) never would have gained as much traction as it did. Instead, Comcast only targeted a small section of politically active and highly intelligent users/abusers of the system. Now, we are all going to be stuck with the resulting mess that is going to drive up the cost of service and likely end the days of unlimited usage plans. Look for by-the-bit pricing to arrive for your home Internet service, very much like you pay for your cell phone surfing, at similar prices -- and you can thank your favorite Broadband activist.

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