At 09:23 UTC the London Data Center experienced issues connecting with PSTN carriers. The issue was quickly identified and resolved at 09:34 UTC. Customers may have noticed calls failing with a 502 response, or being canceled and receiving a 487. Some calls may have been terminated early due to Session Timers expiring.
Connectivity on a Network Interface Card in our London Data Centre caused calls to be unable to initiate, and calls did not failover to a different server automatically.
To avoid a situation like this from happening again in the future we are planning the following preventative actions: