Information about the users on each system is distributed within the network. That allows users to resume activity when their home system is not available.
The system on which the user record was created holds their full user setting. That includes their telephony settings, personal directory and call log. This is that users' home system.
All other systems in the network receive basic details of the users on other systems: the user's name, extension number, login code, home system and current (if hot-desked) system. This information is sufficient for other systems to correctly route calls to users when required.
When a user logs in at another system, that system requests their full user settings for their home system.
User resilience is configured by the Backs up my IP Phones settings, even if the system does not host any IP phones.
How does resilience affect this
When the line from a system to a remote system is set to support IP phone resilience, then during normal operation that remote switch also receives a backup copy of all the system's user settings. That is regardless of the user's currently associated phone type.
If for some reason, the user's home system is no longer visible on the network, after 3 minutes the failover system begins supporting any requests for the other system's user records.
For IP phone users, this allows them to continue using their phone once it has re-registered with the failover system.
For all users, it allows them to hot desk onto any phone on the failover system with their full settings. It also allows them to hot desk with their full settings onto phones on any other systems that are still in the network with the failover server.
When does user failover occur?
If the home system is not visible to its failover system for at least 3 minutes and IP desk phone resilience has begun.
The failover delay ensures that resilience is not invoked when it is not required, for example when the home system is simply being rebooted to complete configuration changes.
When does user failback occur?
After the home system has been visible again for more than 10 minutes.
The failback delay helps ensures that the home system has fully recovered and is stable before starting failback.
Limitations
Resilience fails if the failover server is restarted during failover. The backup user settings received by the failover server during normal operation are held in its non-permanent memory. If during failover operation the server is rebooted, those records are lost.
Internal twinning is not supported during resilience failover.
Fallback twinning is supported during failover. However, only after the phone has registered with the failover server.
