Active Call Preservation

Phones and trunks using direct media may be able to continue existing calls when resilience first occurs. Additional settings can be configured to ensure that the start of resilient mode operation does not interrupt those calls.

When using direct media, the audio part of the call is no longer routed via the telephone system. The telephone system is only involved when any of the parties in the call requires call signaling. This means that the call audio can continue without requiring the telephone system. So long as the call data routing remains in place, the call may continue even if the telephone system is no longer visible for some reason. However, this is not guaranteed.

Media Connection Preservation (MCP)

On calls involving links between systems, the invoking of resilience mode can potentially interrupt existing calls as re-registration occurs. Media connection preservation can help prevent this if required. This feature is supported for the following telephones on IP Office Release 9.1 or higher. It can be applied to calls between systems and via SIP trunks:

IP Office Release 9.1+ : 9608, 9611, 9621, 9641

IP Office Release 11.0+ : J139, J159, J169, J179, Avaya IX Workplace


On those phones, if a call experiences end-to-end signaling loss or refresh failures but still has an active media path, call preservation allows the call to continue. While preserving a call, the phone does not attempt to re-register with its call server or attempt to failover to a standby call server until the preserved call has ended. The maximum duration of a preserved call is two hours after which it is automatically ended.

Calls on hold and calls to hunt groups are not preserved. Only the following call types are preserved:

Connected active calls.

Two-party calls where the other end is a phone, trunk or voicemail.

Conference calls.


During a preserved call the only permitted action is to continue speaking and then end the call. The phone’s softkey actions and feature menus do not work.

Call preservation can be enabled at the system level and for individual trunks. The system level setting control use of call preservation on the system’s IP Office lines and H.323 IP phones. All systems in the network must be configured for call preservation to ensure end to end connection support.

By default, the system setting is also automatically applied to all SIP trunks. However, the trunk setting for each trunk can be individually altered.

When does media connection preservation occur?

This is an immediate feature applied to all qualifying calls currently in progress. It ends when the call ends.

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