Limitations during failover or failback
Limitations of the phone when the phone is in the process of failover or failback are as follows:
• Held calls are dropped.
• Calls that are in the middle of the conferencing or transfer set up are dropped.
• Calls in the dialing or ringing state might not be completed.
• Emergency calls might not work depending on the stage of failover and the functionality
available on the alternate server.
• Incoming calls might not be completed, or they might get diverted to voicemail.
• Message Waiting Indicator is cleared.
Preserved call
When there is a call in progress and a loss of connection occurs between the phone and the
proxy, an attempt is made to preserve the audio path between the phone and the far end. This is
called Call preservation. In most cases, call preservation is successful. However, there are
conditions when the audio path is lost. This loss of audio might happen when there is no direct
path between the phone and the far end. The entity that connects the media between the two
ends is also affected by the loss. Further, there are limitations to modify a preserved call.
Limitations of call preservation
A call is preserved on a best effort basis. A call is preserved on a best effort basis. If the audio
path is directly between two devices and there is no network issue between the two devices, the
audio path is preserved. If the audio is anchored by a device in the middle, for example, a gateway
or conference server and that device is affected by the network outage, there will not be any audio
path. In a preserved call, the phone does not support call features, for example, conference call,
call transfer, and call forward . The reason is loss of signaling between the phone and the SIP
proxy that was used when the call was initially established.
The loss of signalling between the phone and the originating proxy also limits the call control
between the preserved calling parties. For example,
• Calls cannot be transferred.
• Call conferencing cannot be initiated.
If a user disconnects a preserved call, the other end might not be disconnected because of the
loss of signaling.
Failover and survivability
December 2018 Installing and Administering Avaya J100 Series IP Phones 180
Comments on this document? infodev@avaya.com
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