The Pig Problem


Comcast’s high-speed Internet service has been in the news again. For the wrong reasons. 

The Washington Post reported this month that the operator cut off service to subscribers whose bandwidth usage exceeded the norm. "I thought it was unlimited service," griped one alleged bandwidth-hog, whose teenage son evidently was slurping too many bits.

Comcast’s crackdown on another presumed bandwidth abuser made national headlines earlier this year, after the Utah man who had his Net connection yanked complained bitterly on his blog.

So how much downloading is too much?

Comcast won’t release a specific bandwidth ceiling, but a company spokesman told the Washington Post that a subscriber downloading 1,000 songs per day would trigger a disconnection warning. Assuming an average of 3 megabytes per song, according to Wired’s calculations, that’s 3 gigabytes per day, although the Wired blog item includes a disclaimer at the top prompted by a call from Comcast P.R. emphasizing that the 1,000-song example was provided "only as an example."

So, 1,000 songs, 10,000 songs per day–whatever. The real question is, What bandwidth limits will Comcast enforce once it begins offering its tantalizing up-to-200-megabit-per-second wideband cable modem service? CEO Brian Roberts said earlier this week that Comcast expects to start selling wideband services next year.

If Comcast has a problem today with corner cases on its 8-Mbps service, imagine the can of worms (pigs?) that a 200-Mbps tier is going to open up.

The issue is this: High-speed Internet networks aren’t architected for everyone to be consuming their full pipe. 

Motorola estimates broadband concurrency rates to be somewhere around 0.25%, meaning on average only a quarter of a percent of the potential bandwidth available to subscribers is actually being used at any given time. (Say there are 750 homes in a node, half of whom are subscribers to a 100-Mbps service; with a 0.25% concurrency ratio that’s 94 Mbps average bandwidth to the node.) 

That is highly oversubscribed, compared with traditional phone networks or even VOD. And while real-world usage statistics bear the 0.25% concurrency model out, that’s only assuming more people don’t start gobbling bandwidth 24/7. If everyone in the neighborhood is tuning to some Joost-like video service, all the time, the model breaks.

This issue, of course, does not apply exclusively to Comcast. Every other ultra-high-speed provider, including Verizon FiOS Internet, is going to have to stare this one down. One suggestion, floated by Motley Fool’s Larry Rothman: Why not just charge the pigs extra?