In the remote disaster recovery (DR) and local regeneration scenario (without considering registration update), assume that user A is a SIP user in the central site and user B is a PSTN user outside a branch site, User A calls user B through the gateway in the branch site. User A and user B are engaged in an ongoing call. At this time, the active device breaks down due to the central site power outage. Then, the standby device takes over services from the active device. In this scenario, which of the following statements is CORRECT?