berg'd Bryan Berg's blog

Comcast responds to my previous post

It’s been incredible to see the interest in this story that has developed over the last few days. The response to my little hobby project (intended mostly to force myself to start writing blog posts again) has been pretty amazing to read. Comcast responded to some “chatter” (which is PR-speak for this blog, I like to think) with first a defensive rebuttal and finally some real change for consumers, which is far more than I imagined would happen.

I’ll start with the positive changes. Comcast agreed to raise the monthly data cap on for all of their subscribers by 20%. This change is long overdue. Comcast introduced data caps in October of 2008 with a promise to reevaluate the caps periodically. Only now, nearly four years later, have they made good on that promise, and only by 20%. Much more important than the increase in data cap is the implementation of a concrete policy as to what happens when you exceed your cap. The previous policy was merely to merely cut off users who repeatedly exceeded their caps. The new policy (currently in “trials”) introduces usage-based pricing above the cap threshold. Ultimately, this is more fair; as a former network operator myself, I recognize the need to manage the data usage of individual customers. But given the importance of broadband, and Comcast’s near monopoly in many markets, Comcast shouldn’t be allowed to refuse service to customers just because they watched too many hours of Netflix video.

So, that’s the good news.

But this policy change doesn’t go far enough. Comcast still asserts that their Xfinity streaming service is exempt from the cap. By merely doing this, Comcast is treating their traffic differently from other video streaming traffic and is thus violating the terms of the consent decree. In the decree there are two conditions related to treatment of network traffic, neither dependent upon the other; not until the second condition is “prioritize” even used.** Just treating the traffic differently is sufficient to violate the agreement.** Comcast confirmed my assertions in their first blog post by indicating that: a) they use DSCP values to map IP traffic into separate DOCSIS service flows, and b) these flows are exempt from the rate limits imposed on other Internet traffic. Additionally, as I’ve demonstrated in my previous post, the traffic on these separate service flows uses the same RF channels as other traffic.

Comcast goes on to say (emphasis mine):

Specifically, we provision a separate, additional bandwidth flow into the home for the use of this service — above and beyond, and distinct from, the bandwidth a customer has for his or her regular Internet access service. Our Xfinity TV content is provided through the Xbox over that separate service flow, and therefore does not use a customer’s provisioned Internet service capacity.

Let’s talk about limits versus capacity. The amount of capacity provisioned to my neighborhood is the sum of the bandwidth of each DOCSIS channel visible to my cable modem. Given the number of homes this passes—probably in the hundreds—this capacity is massively oversubscribed. That’s absolutely fine, of course; in order for this network to be financially viable, oversubscription is a given. To manage this, Comcast artificially limits the bandwidth available to my IP address to 25 Mbit/s (which is what is standard with my Blast service tier.) This is merely the CMTS imposing a logical limit on the amount of traffic that can pass to my home in any given second.

On the other hand, when using the Xfinity app on my Xbox 360, this limit does not apply. When Comcast says that the Xbox traffic “does not use a customer’s provisioned Internet service capacity,” they are, at best, stretching the truth. The Xbox traffic does not apply to my limit, but no additional capacity is made available. The same amount of capacity is used to provide service to the Xfinity Xbox app as would be used by an equivalent stream being consumed by the Netflix Xbox app, even if the limiting behavior is different. Before the introduction of the Xfinity Xbox app, all of this capacity was available for Internet service.

This distinction is important when the discussion comes to prioritization. In general, prioritization is impossible to clearly observe in the absence of congestion. My previous test clearly showed that Comcast was treating Xfinity traffic differently than Netflix traffic in terms of the artificial limit. I was unable (unwilling, rather) to create congestion for my entire neighborhood, and thus the treatment of this traffic in the face of actual downstream congestion is as yet undetermined. I believe this very narrow definition is what Comcast is using when they say they aren’t prioritizing traffic. Because I can’t measure this, I can’t verify or disprove this claim, though I remain skeptical as to whether that is the case.

Just as a note, I’ve enabled comments only for verified users. The comments section was taking a turn towards a place I was not willing to let it go. I won’t tolerate comments which attack others.