Internet Founding Father Calls Out Comcast On Their Data Caps

05.23.12 5 years ago

We mentioned a while back that Comcast had decided that they would just stone-cold ignore the rules over net neutrality, declaring that using their streaming apps and other goodies on the XBox 360 wouldn’t count against customer data caps.

That smells bad to a lot of people, including Vint Cerf, one of the key players in writing TCP/IP, and essentially one of the founding fathers of the modern Internet.

For the nerds in our audience, here’s how it breaks down:

Comcast acknowledges it is applying a different quality of service value (known in the industry as Differentiated Services Code Point, DiffServ, or DSCP value) that normally denotes priority levels for traffic. But the company states, “that is not their only application—and that is not what they are being used for here.”

Within that DSCP value, there are a number of ranges of possible sub-values defined as a way to manage traffic. These have names like Class Selector, Assured Forwarding, Expedited Forwarding, and others. In this case, Berg and Dan Rayburn both showed that Comcast appears to be primarily using the Class Selector value to distinguish its traffic. This has a range of values from CS1 (lowest value, also known as “bulk”) to CS5, which takes higher priority. The company is taking advantage of this 6-bit field in the IP header of each packet as a way to distinguish the Xfinity traffic as it is sent down to the customer.

Essentially, what Comcast is trying to claim here is that they aren’t prioritizing traffic, even though they’re, uh, using a technology designed to prioritize traffic to mark some traffic as different from others. But one thing even Comcast can’t deny is that their claim that the Internet comes from servers and their traffic comes from a magic separate Internet is pretty much total crap.

Unfortunately, it’s not completely clear; technically, since the Xfinity channel isn’t faster, it might not be a violation of net neutrality rules. On the other hand, we also have to wonder how, exactly, Comcast is going to justify to government officials that the same content, from the same connection, using the same equipment, can be capped or not capped on Comcast’s say-so.

(Image via Steve Garfield on Flickr)

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