T-Mobile Blames Network Failure on a Fiber-Circuit Supplier

Scott Moritz (Bloomberg) -- T-Mobile US Inc. said its nationwide service outage Monday stemmed from the failure of a Southeast fiber circuit that was leased from a wholesale network supplier, which triggered an overload and a “traffic storm.”

As many as 68 million of T-Mobile’s wireless customers had their mobile connections disrupted for several hours as the company tried to identify the problem and restore service.

With the help of hundreds of engineers and technicians, T-Mobile traced the root cause and fully restored service by 1 a.m. New York time on Tuesday, the carrier said. T-Mobile didn’t name the fiber-circuit supplier.

The company’s technology chief, Neville Ray, issued an apology on social media and on the T-Mobile website. “We did not meet our own bar for excellence,” he said.

T-Mobile is working with vendors “to add permanent additional safeguards to prevent this from happening again,” Ray said in his website post. He said the company is continuing to work on determining what exactly caused the initial overload failure.

The episode was the first big test for the company since it absorbed Sprint Corp. in April, after a two-year battle for regulatory clearance. The Federal Communications Commission took notice.

“The T-Mobile network outage is unacceptable,” FCC Chairman Ajit Pai tweeted Monday evening when he announced that the agency would launch an investigation. “We’re demanding answers -- and so are American consumers.”