Following a trend set by other carriers, AT&T has begun sending SMS warning messages to the top 5 percent of unlimited data users on its network. The message alerts consumers that they are among AT&T's top 5 percent that billing period, and suggests they use Wi-Fi to avoid reduced data speeds in the future.

Although it's a pain to those affected, AT&T is being transparent about the issue, giving subscribers a chance to minimize their usage before getting their data speeds choked. Verizon began throttling users who consume a large amount of data, but didn't initially reveal the policy to the public, describe how it would be implemented or describe if and how users would be notified.

It should be noted, however, that AT&T was the first carrier to introduce the tiered data plan structure to customers, setting the trend for other carriers to follow suit thereafter.

AT&T did away with its unlimited data plan shortly after the iPhone 4 debuted last summer, replacing it with a tiered data structure. However, many users are still grandfathered into the unlimited plan. For more recent subscribers, the most robust data option is a $25 per month 2 GB plan that allows you to go over that limit for $10 per extra GB. AT&T confirmed it would throttle the data speeds of the heaviest users remaining on the unlimited plan on its network in late July.

Verizon has a similar policy. The carrier will reduce data speeds "periodically for the remainder of your then current and immediately following billing cycle" if you fall within the top 5 percent of heavy data users. This is done in order to "ensure high quality network performance" for other users, especially in times and locations where there's peak demand. According to a developer forum, Verizon will call and then send a letter to users who are about to get their data speeds throttled. Verizon eliminated its unlimited data plan in July and now offers 2 GB for $30/month, 5 GB for $50 monthly and 10 GB for $80 monthly.

T-Mobile offers an unlimited data plan that costs $100 per month, but throttles users who exceed 5 GB in a single billing cycle.

That leaves Sprint as the only carrier that still offers an unlimited data plan without any kind of throttling (unlimited data and minutes for $100/month), but the carrier does tack on a $10 "Premium Data" fee for smartphone owners. Sprint is rumored to begin carrying the iPhone this year, which would make it the only carrier to allow users an unlimited data plan with the popular phone.

Business analyst and Redditor Zaied Ali was one of the recipients of AT&T's recent round of SMS alerts. He used between 11 and 12 GB of data this month, but normally averages around 6 GB to 7 GB. Ali thinks that AT&T's throttling policy reduces the utility of his smartphone, since he has to think twice about how he uses his phone.

"What is the point of a Netflix app if we don't have the back-end to fully support it?" Ali says.

Another Redditor, Skelatwork, amassed a similar level of data this billing period and received an SMS warning. Skelatwork said that he reached the 11 GB mark by listening to podcasts and Pandora on his commute to work. "I have signed a contract for an unlimited data package. It's my data, I'm going to use it however I please," he says.

A Wired.com poll of 11,000 data plan subscribers showed that 73 percent use less than 2 GB of data each month. Consumer Reports similarly found that the average iPhone user only gobbles 273 MB of data each month. So right now, the throttling issue is generally only affecting a small number of users.

As the use of cloud storage and streaming music and video services becomes more widespread, the issue of these data caps and speed throttling is likely to get more heated.

Updated October 3 at 10:44 AM to clarify that AT&T's throttling policy only affects customers with unlimited data plans.

via Reddit

Image: TheReverendZ/Reddit