Making good on Chairman Ajit Pai’s vow to investigate a major recent outage on T-Mobile US’ network, the Federal Communications Commission is asking for information from individuals, businesses and first responder agencies who were impacted by the outage to try to determine the extent of the impact, particularly on 911 calls.

“The Public Safety and Homeland Security Bureau is conducting an investigation into this outage given the large area affected and the critical importance of dependable and resilient 911 service throughout the United States,” the FCC said. It asked for state and local governments to weigh in (pdf) with information including estimates of how many calls were impacted, whether data services that first responders rely on were affected, and how Public Safety Answering Points learned about the outage and how/whether it impacted their operations. It also asked consumers and businesses to comment on how the outage affected them.

Around noon on June 15, T-Mobile US has said that users experienced what CTO Neville Ray described as “a voice and text issue … specifically with VoLTE (Voice over LTE) calling” that was due to a leased fiber circuit failure from a third party provider in the Southeast, which ultimately resulted in an IP traffic storm that created “significant capacity issues across the IMS (IP multimedia Subsystem) core network that supports VoLTE calls.”

Ray said in a blog post on the outage that “Data connections continued to work, as did our non-VoLTE calling for many customers and services like FaceTime, iMessage, Google Meet, Google Duo, Zoom, Skype and others allowed our customers to stay in touch. Additionally, many customers were able to use circuit-switched voice connections and customers on the Sprint network were unaffected. VoLTE and text in all regions were fully recovered by 10 p.m. PDT last night.”

In the wake of the incident, Pai tweeted “The T-Mobile network outage is unacceptable. The [FCC] is launching an investigation. We’re demanding answers–and so are American consumers.”

T-Mobile US has not specifically addressed the extent to which 911 calls were impacted by the outage, but several local first responder agencies alerted their communities via social media that there were issues with 911 calls specific to T-Mobile US. The FCC noted that the Greater Harris County 911 Emergency Network in Texas warned people that they should use landlines or other devices to call 911, and that the police department in Redmond, Washington tweeted that its dispatch service had confirmed they were “unable to receive 911 calls from T-Mobile callers.”

RootMetrics testing teams on the ground in 10 cities around the country told RCR Wireless News that they began to see 100% call failures in nine out of the 10 markets, but their testing focuses on calls from device-to-device within a carrier network and to/from different carrier networks, not on 911 calls specifically.

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Categories Carriers, network outage, T-Mobile US
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