FCC study pins all blame on AT&T for massive mobile outage

The errors and foibles that led to AT&T’s massive mobile network outage in February that impaired millions of devices and blocked millions of voice calls were “all attributed” to the carrier, the FCC’s Public Safety and Homeland Security Bureau concluded in its damning assessment of the outage.

The FCC’s 29-page report (PDF) found that the size and scope of the outage resulted from a litany of factors that fell at the feet of AT&T, including a configuration error, a lack of adherence to the company’s internal procedures, a lack of peer review, inadequate lab testing and insufficient safeguards and controls to ensure approval of changes that impact AT&T’s core network.

The FCC’s report arrives five months after a misconfiguration of AT&T’s network during a routine maintenance window in the wee hours of February 22 sparked the outage.

Misconfiguration led to a massive outage

Per the FCC’s description of the event, the misconfiguration delivered by an employee – and done without proper peer review – was not detected before it was introduced into the AT&T network. That caused AT&T’s network to enter “protect mode” and trigger “an automated response that shut down all network connections to prevent the traffic from propagating further into the network,” the FCC explained.

The outage occurred at 2:45 a.m. Central Time, roughly three minutes after the misconfigured network element was put into production, the FCC said.

“The shutdown isolated all voice and 5G data processing elements from the wireless towers and switching elements, preventing these services from being available,” the FCC explained in the report.

Based on info provided by AT&T, the FCC said the outage affected more than 125 million registered devices, blocked more than 92 million voice calls, and prevented more than 25,000 calls to 911 call centers across all 50 US states, Washington, DC, Puerto Rico and the US Virgin Islands. The outage also impacted FirstNet subscribers, which AT&T prioritized when it moved to restore service.

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