Blog Post

He said, she said: Is Comcast prioritizing traffic or not?

Stay on Top of Enterprise Technology Trends

Get updates impacting your industry from our GigaOm Research Community
Join the Community!

Comcast, (s cmcsa) once again, has some explaining to do. An engineer has conducted experiments that he says show the nation’s largest broadband provider is prioritizing traffic– something it’s not supposed to do under the conditions the government imposed when the cable company bought NBC-Universal. At issue are the methods and arguments Comcast uses to exempt some of its Xfinity on-demand traffic from its broadband cap.

Comcast categorically denies it’s prioritizing traffic, but the issue is sure to dog the cable provider in the near term, much like the back and forth that ensued back in 2007 when it was caught blocking P2P traffic. Comcast sent me the following statement:

“It’s really important that we make crystal clear that we are not prioritizing our transmission of Xfinity TV content to the Xbox (as some have speculated). While DSCP markings can be used to assign traffic different priority levels, that is not their only application – and that is not what they are being used for here. It’s also important to point out that our Xfinity TV content being delivered to the Xbox is the same video subscription that customers already paid for and is delivered to their home over our traditional cable network – the difference is that we are now delivering it using IP technology to the Xbox 360, in a similar manner as other IP-based cable service providers. But this is still our traditional cable television service, which is governed by something known as Title VI of the Communications Act, and we provide the service in compliance with applicable FCC rules.

After two separate blog posts appeared last week showing that Comcast was labeling packets on its network with different quality of service marks, many folks in the industry raised their eyebrows and a few started feeling around for people to conduct reliable tests. I spoke to people in ISPs, Washington circles, and at web companies about Comcast’s actions. They noted that it did look like Comcast was marking packets, but proving that it was prioritizing them in defiance of the FCC and DoJ merger conditions wasn’t obvious.

Proving prioritization is no easy task.

Meanwhile Bryan Berg, the Founder and CTO at MixMedia was making a mess in his living room trying to prove that Comcast wasn’t just trying to mark its traffic for counting elements of it against a cap, but was indeed giving its Xfinity service delivered via the Xbox precedence over normal traffic. From the blog:

What I’ve concluded is that Comcast is using separate DOCSIS service flows to prioritize the traffic to the Xfinity Xbox app (so that I’m using consistent terminology, I’m going to call this traffic “Xfinity traffic” in the rest of the post). This separation allows them to exempt that traffic from both bandwidth cap accounting and download speed limits. It’s still plain-old HTTP delivering MP4-encoded video files, just like the other streaming services use, but additional priority is granted to the Xfinity traffic at the DOCSIS level. … In addition, contrary to what has been widely speculated, the Xfinity traffic is not delivered via separate, dedicated downstream channel(s)—it uses the same downstream channels as regular Internet traffic.

He then offers some speculation that Comcast is actually paying more per bit to send its Xfinity traffic via the Xbox and back around to the end consumer, which means that this prioritization isn’t done to save Comcast money. The obvious reason he implies, is because Comcast wants to create an unfair advantage over other video-streaming apps that will fall under the cap. An argument that I and several other people have made.

Berg’s chart showing Xfinity over Xbox traffic getting prioritized despite Berg flooding the connection.

Berg’s post is detailed (it has pretty charts!) and Berg lays out his methodology and offers the code he used, so others can replicate his experiments. I’d be curious to hear if others have tried to prove that Comcast is prioritizing traffic, and what they are discovering. Comcast clearly says it is not, but it also vehemently denied that it was blocking P2P packets back in 2007 and 2008 even though the results of it’s actions ended up in P2P downloads getting blocked.

Comcast’s actions violate two principles.

So, if Comcast is prioritizing its Xfinity traffic going over the Xbox, there are two problems that will have to be addressed: one related to Comcast and the other related to the FCC’s regulations covering network neutrality.

For Comcast specifically, when it received approval to purchase NBC-U, the DoJ and FCC said it would have to follow certain merger conditions. Those conditions explicitly state it can’t treat its own traffic differently under its cap, and many people believe that its decision to exempt Xfinity traffic streamed via the Xbox was alone a violation of the agreement.

Now, however, if the FCC can prove that Comcast is prioritizing certain elements of its own traffic, then it is clearly violating those conditions. Of course, then the FCC or the DoJ, would have to take some kind of action against Comcast, and so far both agencies have proven slow to react to other allegations that Comcast was violating its merger conditions. From the conditions:

If Comcast offers consumers Internet Access Service under a package that includes caps, tiers, metering, or other usage-based pricing, it shall not measure, count, or otherwise treat Defendants’ affiliated network traffic differently from unaffiliated network traffic. Comcast shall not prioritize Defendants’ Video Programming or other content over other Persons’ Video Programming or other content.

The second issue is a larger problem for the overall industry, and deals with a loophole in the FCC’s network neutrality regulations that were proposed in 2010 and are currently the subject of a lawsuit filed by Verizon (s vz). The regulations don’t forbid what Comcast is doing specifically, but exempting Comcast’s own Xfinity service delivered via the Xbox (and TiVo) from its data cap is a roundabout way to discriminate against other traffic that isn’t exempt. In that sense it violates the spirit of the regulations. Which means that the merger conditions are largest stick that opponents can wield against Comcast’s actions.

So what’s next on the regulatory front?

Most of the people I spoke with who have experience in politics expect that if Comcast is challenged it will be on the economic advantage is has created for itself because it owns both the last-mile access, a cable business and a content company. Unfortunately such a challenge ignores the fundamental problem with U.S. broadband: it’s not very competitive and the agency charged with regulating it has classified cable Internet as something that lays outside of its authority (for the details on this fight see this GigaOM Pro report (sub req’d).

Ironically the fight that stripped the FCC of much of its authority to regulate cable services, and still to this day puts its network neutrality rules on somewhat shaky legal ground was Comcast’s lawsuit against the agency, after the FCC had censured the cable company for blocking P2P traffic. Comcast is playing a long game here, and it’s unclear how far the FCC can push to protect consumers against its behavior even if it wanted to close that loophole in its network neutrality rules. For now the best bet for enforcement is the NBC-U conditions. Too bad they expire in January 2018.

Comcast van image courtesy of Flickr user Titanas.

14 Responses to “He said, she said: Is Comcast prioritizing traffic or not?”

  1. Phillip Dampier

    Comcast, as usual, is talking out of every side of its mouth. In an effort to justify their unjustified usage caps, they have pretzel-twisted a novel way out of this Net Neutrality debate by paving their own digital highway on a Comcast private drive.

    Comcast argues their 250GB usage cap controls last-mile congestion to provide an excellent user experience. That excuse completely evaporates in the context of its new toll-free video traffic.

    DOCSIS 3 technology has vastly expanded the last mile pipe into subscriber homes. If Comcast can launch their own private pipe for unlimited IPTV traffic that travels down the same wires their Internet service does, they can comfortably handle any additional capacity needs to support their “constrained” broadband service without the need to limit their customers’ use.

    Usage caps remain an end run around Net Neutrality. By combining usage caps on the public Internet lanes and a private, toll-free traffic lane for their own content and that from their “preferred partners,” customers will gravitate towards the free lane to protect their usage allowance. You don’t have to de-prioritize traffic from your competition, you just have to limit it.

    That is why Netflix is foolish to argue that Xfinity’s video traffic should count against Comcast’s arbitrary usage cap. The real issue here is whether Comcast should be capping any of its Internet service.

    Comcast has given us the answer, launching the very bandwidth-intense video streaming it used to decry was helping to create an Internet traffic tsunami.

    It’s time for Comcast to drop its usage cap.

    Phillip M. Dampier
    Editor, Stop the Cap!

  2. I like how Tony Werner basically admits that yes, they ARE discriminating/prioritizing, while trying to claim they are not.

    What next, Comcast claiming their peering policy makes business and technical sense?

  3. Tom Lazlo

    A few questions looking for clarification on Tony Werner’s comments:

    1. He says “we provision a separate, additional bandwidth flow into the home for the use of this service”. Fine. But the issue with this statement is that the last-mile bandwidth over a DOCSIS HFC network is limited and shared. That “additional” bandwidth has to come from the limited pool of DOCSIS bandwidth available to the customers on that HFC network segment. If there is free bandwidth available (i.e. not in use at the time) then no problems. But what about when there is no additional bandwidth available (i.e. during periods of congestion)? How does the CMTS prioritize the Xbox video traffic compared to the Internet traffic during times of congestion? Does the Xbox video traffic get treated the same as the best-effort Internet traffic and drop packets during times of congestion? If not, then he is being disingenuous with his priority comments.

    2. He also states “Your Xbox 360 running Xfinity TV On Demand essentially acts as an additional cable box for your existing cable service”. However, the Xbox is not a single function dedicated device like a cable box. It is primarily an Internet connected gaming machine. Clearly you are not adding “a separate, additional bandwidth flow” for all of the Xbox gaming traffic or even the Xbox Netflix traffic. This implies four things:
    I. You are using Deep Packet Inspection to identify the types of traffic coming from the Xbox and using this to separate the traffic into different service flows.
    II. This means you are using your position as the Internet Service provider and owner of the “pipe” to your advantage over the other Over-The-Top video traffic.
    III. The “separate, additonal bandwidth flow” is simply a “virtual” separation of the traffic and not based on hardware like a dedicated cable box would be.
    IV. If you can identify and separate out your Xbox video traffic, you could identify and separate out all video traffic to Internet connected devices like the Xbox.

    All of which means that if my assumptions are true, Comcast is using its position as the Internet Service Provider to identify and discriminate against certain types of Internet traffic which is clearly a Net Neutrality violation. Calling it “traditional cable televison service” does not hold water in the era of converged services over the Internet.


    • Guest

      Stat-mux sharing is present in all IP networks. There is nothing unique about this. With proper capacity planning there is no issue with converged IP pipes. There are a number of public studies from the FCC SamKnows to Speedtest to Akamai to Netflix’s own performance ratings that show downstream capacity is properly maintained for optimal performance of all services. That said if it wasn’t and was an issue BOTH the Xbox and Internet traffic would be negatively impacted.

    • Bobby

      As someone who has built out DOCSIS infrastructure, and designed DOCSIS service flows, I completely agree with Larry’s comments. I wish more people had a technical understanding of how DOCSIS works so that they would know exactly what Comcast is doing. It is not at all neutral.

  4. Nathan

    First off, Stacey and Gigaom, thanks for the consistently high quality coverage.

    My worry is the precedent that is being set. If they (Comcast, Verizon, AT&T etc) get away with this, what next? Seeing that Comcast owns NBC and Universal, will they relegate CBS, ABC, Fox and others to a lower class of traffic and make it count against my cap while delivering NBC shows via their preferential “service.”

    If I want to watch The Avengers via broadband, I would hate to be forced to watch American Reunion from Universal because of some opaque technical favoritism that Comcast affords its own assets.

    Outlandish? That’s what I first thought when Netflix first raised this issue. I know better now.

  5. Guest

    That depends on your definition of priority. Your argument doesn’t discount the fact that they are giving the Xfininty video service an unnatural advantage over Netflix. In that regard, they are most definitely giving their service priority over a competing service.

    • deeceefar2

      I would absolutely agree with this. If I force everyone to stand in a line at the TSA and wait to be groped. Then later down the road I single out people to be certified Americans, and then add and additional 8 lanes of groping. I’m prioritizing, not on the individual level, but on the group level. I said I’m going to invest in this new line for certified Americans not the old one.

      This is why the stipulation on the merger existed. Comcast cannot allowed to leverage their granted local monopoly to force people to use their video services on a micro market and not compete in the market they were granted a monopoly for.

      • deeceefar2

        How Uverse or FiOS TV work isn’t really at issue here. Comcast is out on its own right now because it is buying a TV Network, and in the spirit of their negotiations to purchase the company they aren’t supposed to be creating a 2nd tier of internet.

        But in this case you are looking a very narrow technical definition on a micro scale without considering the overall picture. They have created a second lane of IP traffic that is not regulated like the rest of the IP traffic. The express purpose of this IP traffic is to provide a better quality of service to this particular set of traffic that no other traffic can get. The next logical step for them is to leverage this to provide an entire class of data services that only they have access to.

        You might say well that is fine because they aren’t prioritizing anything, but as I pointed out in the analogy above you can prioritize your investment in such a way as to create a defacto priority. They merely need to stop investing in internet traffic and in a few years time it will work itself out. They’ll have the only service capable of offering 4k 3D Holographic TV or whatever else is on the horizon because they have a monopoly and don’t have to compete on data services they can chose to invest only in video services for their own networks.

  6. Guest

    I think the chart clearly shows that new bandwidth is specifically added for Xbox service. It is not impacting the Internet service under congestion. That isn’t prioritization, that is adding incremental IP services.

    • deeceefar2

      Not so fast what the graph shows is that the one household received additional internet capacity. Which proves that Comcast isn’t prioritizing the customers own traffic, but that isn’t where congestion occurs anyway. What about the next level up?

      Are they prioritizing Comcast video traffic leaving the node? The only one that can prove that is Comcast, and they didn’t specifically detail how the traffic flowed in their response other then to say it was on their network and not to the “internet.” Well in this case since their network is massive you can go coast to coast inside their network and so that doesn’t really do much to soften the blow of traffic prioritizing.