With servers across the US your system settings are always safe. Whether your internet goes down temporarily or your building is destroyed in a tsunami, your calls will still be routed as if nothings wrong. The call would be routed through the cloud and attempt to ring normally. If it doesn’t see a phone on the other end (IE: Tsunami) it will then ring backup numbers set in place. (Cell phone, Laptop, or just a mailbox if you prefer that you can check from anywhere).