Japanese telco KDDI Corporation experienced its biggest outage ever, which pushed around 40 million customers offline in the wee hours of Saturday morning. The outage began at around 1:35 a.m.
Although internet and communication services have largely been restored, au mobile phones are still having difficulty making phone calls due to a temporary limit placed on network traffic. Around 260,000 customers out of the total 40 million affected belonged to corporate sectors. The outage disrupted payment machines, bank teller machines, parcel deliveries, and even the Meteorological Agency's weather data.
At a press conference, Deputy Chief Cabinet Secretary Seiji Kihara said that the problem is extremely regrettable as mobile networks are important infrastructure for the public and their activities. He also demanded an "in-depth explanation for users" from the carrier.
KDDI President Makoto Takahashi apologized for the disruption at a press conference, admitting that it was the largest outage in the company's history. The carrier is also considering compensating individual and corporate users.
KDDI is Japan's second largest mobile carrier by subscribers. The company says that the problem occurred due to a facility failure before dawn on Saturday. The failure was due to the switching system for voice calls that was replaced during regular maintenance. The repair work triggered a greater concentration of traffic that made the company put limits.
The carrier is taking measures such as flow control to reduce traffic congestion for voice calls and data.
ATMs at Ogaki Kyoritsu Bank, among others, still remain out of service as of Monday morning. Transport company Yamoto Transport Co reported that its delivery system was disrupted. Drivers using Toyota's connected car service were unable to reach a call center or do other tasks too.
The problem also affected low-cost UQ mobile brand and its "povo" mobile customers, as well as other small leasing companies such as Rakuten Mobile Inc.
KDDI recommended people to use landlines or public phones in case of an emergency.