June 15, 2020 T-Mobile Network Outage Report

The causes and impact of a nationwide T-Mobile outage that occurred in June, along with actions that can help prevent similar outages in the future. On June 15, 2020, T-Mobile experienced an outage on its wireless networks that lasted over twelve hours, disrupting calling and texting services nationwide, including 911 service, as well as access to data service in some areas. The FCC’s Public Safety and Homeland Security Bureau estimates that at least 41% of all calls on T-Mobile’s network failed during the outage, including at least 23,621 failed calls to 911. The Bureau notes that T-Mobile’s outage was caused by an equipment failure and exacerbated by a network routing misconfiguration. The outage was also magnified by a software flaw in T-Mobile’s network that had been latent for months and interfered with customers’ ability to initiate or receive voice calls during the outage.

The Bureau identifies the network reliability best practices that could have prevented the outage or mitigated its effects, including providers periodically auditing the diversity of their networks. The Bureau also recommends several network reliability issues for further examination by standards bodies. In keeping with past practice, the Bureau plans to release a Public Notice, based on its analysis of this and other recent outages, reminding companies of industry-accepted best practices, including those recommended by the FCC’s Communications Security, Reliability, and Interoperability Council, and their importance. In addition, the Bureau will contact major transport providers to discuss their network practices and offer assistance to smaller providers to help ensure that our nation’s communications networks remain robust, reliable, and resilient.