While investigating High Availability (HA) in CTI and PBX systems you will often find mention of Call Recovery. Another term you run into is Call Survival, which is often used interchangeably with Call Recovery incorrectly. This is because each is a different approach to solving a problem. The problem being a failure which would interrupt the calls of a system.
With Call Survival when a failure happens the caller and callee do not have to take action to continue their call as it survives the failure. At a high level this is done by reacting to the failure quickly and re-routing the audio path around the failure.
With Call Recovery when a failure happens the recovery is different depending on the system. Sometimes the caller will need to initiate the redial the callee or it could be an automated process but the callee still have to answer this new call.
From a user perspective the better option is Call Survival as they may only experience a momentary interruption in their audio as the path is rerouted around the failure instead of having to re-initiate a call to recovery it.