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Comcast Denies Own Traffic Prioritization
Insists They're Fully Adhering to NBC Universal Conditions
by Karl Bode 10:17AM Wednesday May 16 2012 Tipped by AndyDufresne See Profile
Just when the network neutrality debate appeared to have resigned itself to a dark corner, the revelation that Comcast was exempting Comcast TV content over Xbox 360 traffic from its bandwidth cap rekindled the entire debate. Comcast claims they're simply treating the Xbox 360 as other set top, while competitors like Netflix claim it gives them an unfair advantage in streaming video offerings. "The same device, the same IP address, the same wifi, the same internet connection, but totally different cap treatment -- in what way is this neutral?" recently asked Netflix CEO Reed Hastings.

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Complicating the situation was recent "proof" by several different individuals claiming that Comcast was specifically prioritizing their own streaming services over that of their competitors. You can find the broadest technical exploration of the claim here by MixMedia CTO Bryan Berg, who says he has proven that Comcast is busily playing favorites:
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.

I still believe that DSCP values I observed in the packet headers of Xfinity traffic is the method by which Comcast signals that traffic is to be prioritized, both in their backbone and regional networks and their DOCSIS network. 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.
However, as we noted in our original post (and was pointed out by several readers by e-mail), QoS over a cable network is complicated, and it's very difficult to prove prioritization using DSCP (& IP PREC) tags. A week or so later and Comcast CTO Tony Werner has responded to the claims at the company's blog, stating they in no way are giving their own content a leg up:
There's also been some chatter that we might be prioritizing our Xfinity TV content on the Xbox. It's really important to us that we make crystal clear that, in contrast to some other providers, 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.
As for the Xbox 360, Comcast continues to insist that they're using the device as just another set top box, just utilizing IP. Your thoughts? Is Comcast playing favorites or not?

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reply to UnnDunn

Re: How is this different from FiOS TV and Uverse TV

said by UnnDunn:

said by 28619103:

Isn't this like FiOS TV and Uverse TV?

The difference is neither Verizon nor AT&T impose bandwidth caps on their wired residential broadband plans.

Wrong - U-Verse has a 250GB cap, which their own TV conveniently ignores. Just like Comcast.


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The traffic is not prioritized (so capacity management impacts all services equally). ADDITIONAL bandwidth is added as not to impact your Internet service. On top of that, capacity is managed normally with the downstream while multiple watchdogs (FCC, Netflix, etc) have been measuring this for years with great results as compared with all ISPs.

I'm amazed at all the negative hype around using IP as it was intended to be used. Viva IP Convergence!

Isn't this like FiOS TV and Uverse TV?