Cogent Now Admits They Slowed Down Netflix’s Traffic, Creating A Fast Lane & Slow Lane

Last week when M-Lab published the results of their study on traffic congestion on the Internet, many used it as another example of how the ISPs were the one’s responsible for slowing down or blocking Netflix traffic coming into the ISPs network. But something odd stood out about some of the data M-Lab’s collected, which policy makers and lawyers missed. The M-Lab’s data documented the introduction of a higher level of prioritization somewhere on the network. Prioritization rules that would impact how content is delivered to the ISPs, and would greatly impact the quality of video and other content consumers would receive.

This morning, Cogent admitted that in February and March of this year the company put in place a procedure that favored traffic on their network, putting a QoS structure in place, based on the type of content being delivered. Without telling anyone, Cogent created at least two priority levels (a ‘fast lane’ and ‘slow lane’), and possibly more, and implemented them at scale in February of this year. What Cogent did is considered a form of network management and was done without them disclosing it, even though it was the direct cause of many of the earlier published congestion charts and all the current debates. [See: Cogent’s Favoring Of Packets Disregards FCC Rules]

Cogent said they prioritized data based on user type “putting its retail customers in one group and wholesale in another.” Cogent said “retail customers were favored because they tend to use applications, such as VoIP, that are most sensitive to congestion” and that they “implemented a QoS structure that impacts interconnections during the time they are congested.” Cogent classified M-Lab performance tests into the highest priority class. As they did so, this change instantly and dramatically improved the M-Lab test results. [Described by Susan Crawford as “the Cliff and the Slope” – it appears the cliff was Cogent taking on Netflix and the slope was the introduction of a fast lane on the Cogent network] The fact that the high priority traffic class so quickly improved M-Lab’s test performance demonstrates conclusively that there must have been significant congestion present in Cogent’s network. Cogent now admits to impacting third-party content and says they did it as a “last resort effort to help manage the congestion and its impact to our customers”.

It seems extremely unusual that Cogent implemented this traffic change during the very same week that Comcast announced the Netflix deal. The Comcast and Netflix interconnection deal was announced On February 22 and most of the Cogent changes, according to the M-Lab blog, appear to have occurred within five days starting on February 20. Was this done to influence public debate about the cause & effect of the deal? Remember, Cogent started making critical comments in the press once they started making their prioritization changes, while not disclosing what they had done. And to make this even more interesting, Cogent makes it sound like they only did this in February and March of this year, but Cogent’s priority classes appear to continue to this day, which can be proven by looking at how the packets are being prioritized. If Netflix was aware of their traffic being deprioritized that would be even more interesting. And what about Cogent’s wholesale customers. Were they told their traffic was being deprioritized as well?

As I have been saying for many months, the vast majority of people are laying blame on specific companies without having all the data to really make an informed decision. This new admission by Cogent is just another example of companies playing games, in an effort not to disclose everything that is really going on behind the public’s eye. As far as I am concerned, all companies share the blame in this as they all have to work together to fix the problem and keep consumers happy. But for all the lawyers and policy makers that jump on something the moment it is released, and do a blog post laying blame, I’d like them to now explain what is going on when Cogent has now confirmed they put Netflix traffic in the slow lane.

Updated Nov. 6th: Cogent told Ars Technica that it implemented the network management in a “visible” and “transparent” way, yet the company didn’t discuss it publicly when the system was implemented.

And on Cogent’s website, on their net neutrality page it says: “Cogent practices net neutrality. We do not prioritize packet transmissions on the basis of the content of the packet, the customer or network that is the source of the packet, or the customer or network that is the recipient of the packet.”

Cogent can’t get their story straight.

  • Larry

    dan, whenever you post something that doesn’t take the side of netflix people love to make personal attacks on you, so good luck with this post. all you are doing is pointing out what cogent said they are doing. what i want to know is why the tech community isn’t looking at this and asking questions. you have said before you are not an enginner, but many others are, and cogent just confessed to something it appears no one knew about. the tech community should be asking questions. this is a big deal, cogent never disclosed it, those who are in the networking community for a living should be talking about it.

  • Ralph

    This article implies that because Cogent was using QoS that they had
    internal congestion, but I don’t think that’s the case. If they applied
    QoS then the saturated cross connects are the point where the QoS would
    take effect.

    Without knowing the ratio of High priority vs low priority traffic it’s
    hard to know how this QoS would have affected the low priority traffic
    at the congestion point. Certainly the higher priority traffic would
    look better, but if it was only a small percentage of traffic then the
    lower priority wouldn’t look much worse.

    Doing something to ensure that sip traffic or other low bandwidth
    latency sensitive traffic flowed smoothly across a congested exchange
    point seems like a good thing to be doing and in fact minimizes the
    impact of the saturated link, which is kind of the opposite of what this
    article suggests.

    For example, if you have a saturated 10G link and you prioritize your
    SIP traffic that is ~2% of your bandwidth, there will be minimal impact
    on the non prioritized traffic, and you will have removed issues for SIP
    connections making the issue look less bad.

  • Jeremy

    “The fact that the high priority traffic class so quickly improved
    M-Lab’s test performance demonstrates conclusively that there must have
    been significant congestion present in Cogent’s network.”

    Do we know that the congestion was internal to Cogent’s network? I don’t think we do. What if the QoS was only used to determine which packets were the first to go through the congested Cogent to Eyeball ISP links? If Cogent’s network is internally uncongested, then the QoS has no effect there. I think Cogent can make the case that the QoS only had effect on the congested peer links and was their attempt to make the congestion have the least possible impact on customer experience.

    • Moe

      I think your hypothesis is % right. The QoS was used to address the congestion of the peering links. It would explain the data. I guess they found a way to oversubscribe and differentiate quality. I just wonder if those that got degraded got a discount (and knew about it)

      • tim305

        I wonder that too. If Netflix knew they were signing up for discounted “last effort” service, then their public outcry appears in a different light. Perhaps they got exactly what the paid for. Hopefully, the FCC will use its new powers to investigate and publicize the terms of these deals. How much was Netflix paying Cogent for the service they received?

        On the other hand, if the prioritization only took place after the Comcast-Netflix deal was announced, it looks more like Cogent was simply trying to salvage relations with existing customers, knowing they would not long be doing business with Netflix.

  • Dan Hamstra

    If more ISPs start prioritizing SIP, it will become the new protocol of choice for media delivery. And then it will be some other protocol and on and on as the ISPs and the content providers start playing whack-a-mole with each other and the consumer will continue to suffer from the ensuing instability of performance. I’m not generally a fan of more government intervention but I wish they could figure out some way (that’s agreeable to the FCC and Congress and actually useful, hahaha) to fix this without creating lots of regulations and red tape. Perhaps ICANN or some other entity could be tasked with coming up with routing transparency reporting procedures and then release the data publicly so that public and private research groups could analyze the data and praise/criticize the various players. Any company participating and adhering to certain standards could then tout that they are “NetNeutral Level 1 certified” or some similar thing and market based on it.

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  • Australian

    If it is true that wholesale users were being de-prioritized, then significant problem s have been created for international ISPs with a peering presence in the USA. These are wholesale users and knocking packets off a link at 300ms latency has a much greater effect on TCP throughput than for local users. There have been countless customer complaints about poor speed to the US, and the common thread has been cogentco. Of course they blame the ISP, despite the purchasing of adequate bandwidth.

  • cscooper2000

    Does Cogent have any competitors in their market?

    • Zack Sargent

      Mercifully, yes. Cogent is a terribly operated backbone – one that I have only used as “last resort” when other backbones were down or routing through them was an only option.

      • cscooper2000

        Then what is the point of this article? If Cogent customers aren’t happy with their Netflix Streaming (i.e. if they can tell they’re not getting HD quality streams), then they can cancel their service, forget about Cogent and move on to one of their competitors. Leave the government out of it and save the tax dollars. The free market will determine who wins and who loses, here. When my Time Warner Cable was delivering less-than-promised speeds, I called and complained. Eventually I started looking for alternatives. Fortunately I found one. In some markets there aren’t any alternatives. That’s the only time I feel the government should get involved (i.e. maybe deregulating like the US gov did to the phone companies in the 70s or 80s). Let the free markets compete and you’ll end up with some really excellent competitors (and the government won’t have to grow in the process)!

        • danrayburn

          Point of this article is simple. To inform people of what Cogent was/is doing, since they didn’t disclose it. Would you rather have less info on what’s going on with these kinds of companies or more? We need more transparency.

          • cscooper2000

            Yeah, I get it. I just don’t agree that they are beholden to share all of their decisions (operational, business, accounting, network, or otherwise) with us. Like I said, if I’m dissatisfied with their service, I’m free to go elsewhere. And, for the record, if I was their customer, I would have. Is there a law that says they have to share that information? I’m not clear where exactly Cogent operates, but is there a law in their country that says they cannot “manage their network” without informing the press (or whomever)? I’m sincerely trying to understand what they did wrong? Did they do something wrong? If so, shame on the government. Or did they just do something you hate? If so, shame on you for trying to scandalize Cogent’s actions without making it transparent to your readers (oh wait, that’s not illegal either).

          • danrayburn

            On July 23rd of this year, the FCC put out an enforcement advisory saying that “broadband providers must disclose accurate information to protect consumers“. Cogent admits, they didn’t notify anyone.

          • Zack Sargent

            Curiously, looks like they primarily connect to Netflix via XO. I haven’t looked up every Netflix IP block, so this could not be representative of all things Netflix from Cogent’s perspective:

            BGP routing table entry for, version 2952562286
            Paths: (1 available, best #1, table Default-IP-Routing-Table)
            2828 55095
   (metric 10102021) from (
            Origin IGP, metric 4294967294, localpref 100, valid, internal, best
            Community: 174:10031 174:20666 174:21000 174:22013
            Originator:, Cluster list:,,

            The “Paths:” attribute shows 2828 (XO) to 55095 (Netflix) as the only path in the table.

            A list of Cogent community strings:

            Only one of the communities is listed (174:21000 – learned from North American customer). I’m assuming the other three (174:10031, 174:20666, and 174:22013) have something to do with their traffic shaping policies.

            Okay, I was curious … 🙂

          • cscooper2000

            Thanks, Dan. That valuable bit of information was left out of the article. Knowing that changes everything. I looked up the FCC advisory and read it. You are right. According to the law Cogent should have disclosed. Case closed. Off-topic: While I want transparency from the companies I do business with, I don’t agree with that it’s the government’s place to dictate in these kinds of trivial things. Their duty is to “Protect Consumers”. Experiencing an intermittent, broken 4K stream—or being subjected to the inferior 720p stream—trying to enjoy the latest installment of the Hobbit, while infuriatingly annoying, is hardly putting anyone in harms way.

        • Zack Sargent

          @danrayburn:disqus – Transparency is a funny thing. The Internet has always supported this kind of tool: Now, that doesn’t show their QoS rules, but might be able to read through some of the BGP communities to suss it out. I don’t have time for that, today. In general, yes, I agree that Cogent did a sinister and/or stupid thing, here.

          @cscooper2000:disqus – Less government is usually better, I agree. If you look at major problems of recent years, the BP oil spill was not prevented by regulators, nor was the financial collapse. It’s not enough to have rules – they also have to be enforceable.

          The best solution is to have your municipality do what Kansas City did: Incentivize Google Fiber to come to town. This way, they offered greater competition to their residents: Cable, Telco, Wireless – and now Google. (As the home of Sprint, there’s a LOT of excess fiber available in KC … but that’s another story.) That is the best solution, in my opinion. Give customers more choice; don’t take away possibilities from ISP’s.

        • Aaron Chauncey

          Precisely correct.

  • Anon

    The technical implementation is quite appropriate, percentages of top marked traffic versus de-prefferenced traffic. The problem comes into play from the way Cogent designates Retail vs Wholesale. The designation is entirely based on the facility type; enter at a carrier hotel and your traffic is lower class, enter at a downtown office tower and you are high class traffic.

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