NTT: NTT's Network Down in Japan, Affecting Telecom Operations

On April 3, NTT East and NTT West, subsidiaries of Nippon Telegraph and Telephone (NTT), were impacted by a network outage in Japan. NTT had a significant network outage that morning at about 7:10 local time, according to reports from regional media outlets, albeit the impacted services have since been restored. According to Kyodo News, up to 446,000 Internet links and 233,000 landline telephone connections were disrupted by the outage for NTT's Internet and landline telephone services. 

According to sources, the outage was attributed to a communications system malfunction, and services were resumed a short time later. The network failures affected users in 13 prefectures, including Tokyo, Osaka, Ishikawa, and Ehime. Due to the disruption, NTT Docomo and SoftBank Corp., which both use NTT's optical line services, also experienced connectivity issues. Calls to emergency services like 110 and 119 were also impacted. This outage wasn't quite as bad as the one that affected KDDI Company, a rival Japanese carrier, which in July of last year rendered almost 40 million people nationwide without access to mobile phone service. 

The cause of that specific outage, which lasted all weekend, was given as "equipment failure". In October 2021, two million NTT Docomo customers experienced an outage that prevented them from using voice and data services.