·Time Warner Cable
Points of clarification
U-Verse meters shouldn't be too screwed up...as long as video traffic isn't counted (it doesn't add incremental bandwidth costs like unicast data so it shouldn't be counted...and AT&T probably doesn't want it counted). PPPoE overhead means that, on a 1500 byte packet, you get 1492 bytes of data. So 0.5% inflated.
ATM OTOH is where all bets are off. 53 byte cells carrying 48 bytes of data is 10.4% worth of overhead. Add to PPPoE overhead and you get about 11% overhead. So your 150GB plan just became 135GB.
You can layer in TCP overhead and such beyond that if you really want to, resulting in 86% of the data being sent/received being the stuff you really want, instead of overhead/headers. This brings the overhead count up to 16.2%, giving you around 129GB for your 150GB package.
Comcast's usage meter is much nicer. They filter out all of the multicast/ARP noise (a few GB per month) that happens on a cable system, plus other forms of overhead (Comcast doesn't use PPoE or ATM, so overhead is significantly lower) so you end up with a usage meter that reports LESS than what DD-WRT does. Plus it's a soft cap.
I would say "I hate to say it" but I don't, when you compare to AT&T...Comcast did their meter correctly, and AT&T is screwing theirs up, big time. Especially since the numbers I listed above don't even reflect the reality that people are seeing with the usage meter...the meter is all over the place!
Don't give Comcast too much credit. They implemented their soft cap 10/2008, but could not get a usage meter going at the time of their cap launch. So, we cap you, but you have no idea how much you are using via our accounts page. More corp behemoth, eh we do whatever we want.