AT&T is on the defensive today, saying that its decision to limit the use of Apple's video-call app Facetime does not violate the FCC's net neutrality rules.

Ever since Apple introduced the application, AT&T has limited its use to Wi-fi. In other words, customers who were using the AT&T network could not make video calls using the built-in app. Last week, AT&T changed that policy, saying it would allow customers on its new "shared data plans" to use the app but that did not apply to those who are on unlimited or tiered plans.

As The New York Times reports, this made many unhappy. The Times adds:

"John Bergmayer, senior staff lawyer at Public Knowledge, said AT&T was violating the F.C.C.'s Open Internet Rules, which say that mobile providers shall not 'block applications that compete with the provider's voice or video telephony services.'"'There is no technical reason why one data plan should be able to access FaceTime and another not,' Mr. Bergmayer said in a statement."

AT&T called the reaction "knee jerk" and said groups like Public Knowledge had "rushed to judgement." It is not violating net neutrality rules, it said, because there is a distinction between "pre-loaded" apps and apps that you users can download like Skype.

"The FCC's net neutrality rules do not regulate the availability to customers of applications that are preloaded on phones," AT&T said.

It added that it made the decision to limit access because it was unsure what kind of impact that kind of move would have on its network.

"We will be monitoring the impact the upgrade to this popular preloaded app has on our mobile broadband network, and customers, too, will be in a learning mode as to exactly how much data FaceTime consumes on those usage-based plans," AT&T said in a statement.

Ars Technica reports that many neutrality advocates, including Public Knowledge, disagree with AT&T's reading of the FCC rules.

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