The LTE (4G) mobile phone services of “SoftBank,” “Y!mobile,” Fixed Line Services called “Ouchi-no-Denwa” and a part of “SoftBank Air” services were not available for its use from 1:39 pm to 6:04 pm on Thursday, December 6, 2018, due to our network outage caused by Ericsson-made software errors related to its packet switches, covering our customers nationwide.

We deeply apologize to our customers for all inconveniences it caused. We will strive to take all measures to prevent the same network outage.

1. Period of Network Outage

1:39 pm - 6:04 pm (JST) on Thursday, December 6, 2018

2. Services Affected by the Outage

• “SoftBank” and “Y!mobile” 4G LTE mobile phone service
• Fixed-line telephone service “Ouchi-No-Denwa”
• “SoftBank Air”

3. Details of Impact

4G (LTE) of mobile services under the “SoftBank” and “Y!mobile” brands were not available for use across Japan. Along with this, traffic data surge occurred in the 3G network that caused further difficulties for service use. The same situation occurred for “Ouchi-No-Denwa” and “SoftBank Air” services.

4. The Number of Users Affected by the Outage

Currently under investigation

5. Cause of the Network Outage

At 1:39 pm on Thursday, December 6, 2018, the SoftBank Network Center detected software's malfunction in all of the packet switching machines manufactured by Ericsson, which are installed at the Tokyo Center and the Osaka Center, covering our mobile customers nationwide. After the incident, SoftBank received a report from Ericsson that the software has been in operation since nine months ago and the failure caused by the same software also occurred simultaneously in other telecom carriers across 11 countries, which installed the same Ericsson-made devices.

The network was recovered to the normal operation by adapting the older version of the software to all packet switching machines.

6. Recurrence Prevention Measure

SoftBank will work together with Ericsson and thoroughly investigate this issue to prevent further recurrence.

• The information is true and accurate at the time of publication. Price, specification, contact and other information of products and service may be subjected to change. The information contains certain forward-looking statements that are subject to known and unknown risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such statements.