AT&T Internet usage billing off by as much as 4,700%

How can your ISP count your packets if it doesn't know how to count?


If gas goes up this summer above $4 per gallon, or even $5 per gallon, how comfortable would you be pulling in to a full-service station whose pump dial spun randomly and you were charged according to how many gallons the attendant figured had gone into your tank while holding down the lever and counting "one Mississippi, two Mississippi, three Mississippi" at about 50 cents per Mississippi?

It might happen to your Internet costs if carriers are able to move to usage based billing under current FCC regulations and a shocking degree of their own incompetence.

Two weeks ago, according to a story in, AT&T confirmed that it is putting caps on data customers can download -- 150 GB per month for its DSL customers and 250GB/month on subscribers to its U-Verse fiberoptic service, which offers speeds of up to 24 Mbit/sec downstream.

Customers who go over the limit three times during the entire life of the account will have to pay $10 for every 50GB over the limit.

Usage-based billing is routine for business users, though it's unusual in consumer markets. AT&T and other carriers have experimented with it, to widespread complaints from customers.

Those complaints got louder following AT&T's revelation of the usage-based billing plan when it became clear it had a real problem measuring the volume of data individual customers use.

In one case AT&T's metrics varied so wildly it under-reported one household's usage by 91 percent on one day and over-estimated it by 4,700 percent another.

"...four Mississippi, five Mississippi, six Mississippi..."

It's not clear what the problem is, but DSLReports and many of its telecom-geek readers theorize the measurements come from statistical reports from Digital Subscriber Line Access Multiplexers (DSLAM) devices that merge many DSL lines into a larger IP connection at the exchange rather than the subscriber's house.

Because DSLAM works on OSI level 2 it could misinterpret PPoE and ATM networking overhead as legitimate traffic. That explanation covers inaccuracies of about 30 percent, however, leaving at least one subscriber with 4,740-percent-worth of unexplained discrepancy.

AT&T isn't the only carrier with an arithmetic problem, either.

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