KDDI outage affects nearly 40M in Japan

Japanese carrier KDDI is coming under fire after a network outage that affected nearly 40 million people over three days.

The company said data transmission had mostly been restored by Monday morning, but service restrictions were still causing many users to have trouble making phone calls and sending short messages, the Associated Press reported on Monday.

The nationwide outage started around 1:35 a.m. on Saturday due to a “facility failure” that was tied to a VoLTE switch. Text messaging, phone calls and other services were disabled for more than 39 million users of KDDI’s mobile services.  

The AP said the outage was especially unfortunate because it disrupted emergency calls at a time when people were facing increased risks of Covid-19 and heat strokes and potential emergencies due to an approaching typhoon.  

On Tuesday, Japan's communications minister criticized KDDI over its handling of the situation, saying the company failed to provide sufficient information to customers in a timely manner, the Japan Times reported.

KDDI, which provides the au mobile phone service brand, "has not fulfilled its responsibility as a telecommunications operator," Internal Affairs and Communications Minister Yasushi Kaneko told reporters, according to the Times.

Specifically, the network failure occurred when a router for voice calls was replaced during regular maintenance, with repair work triggering a concentration of traffic that led the company to reduce user access. The carrier then experienced a cascade of technical problems that further prolonged the connection difficulties, the Times said.

An outage last October by rival NTT DoCoMo affected nearly 13 million people.

In the U.S., T-Mobile in 2020 experienced a 13-hour network outage that left many customers without the ability to text or use VoLTE calling. The carrier blamed that on a leased fiber-optic circuit failure that set off a chain of events leading to major capacity issues across T-Mobile’s IMS core network.

At the time, T-Mobile said the circuit failure was tied to leased fiber from a third-party provider in the Southeast, but didn’t say who. That wasn't the only problem, as backups put in place also failed.