Avaya 9601 Administering page 132

System Failover and Survivability
approximately 90 seconds of the time the failure occurs when TCP or TLS connections are used.
Once a failure has been detected, the endpoint completes its selection of an 'Active' controller within
approximately 5 seconds.
With simultaneous registration, available in a multiple SM environment with SIP software Release
2.6, both failover/failback transition time and behavior is minimized.
Related Links
Failover/failback behavior
Deskphone behavior during failover
During failover, 9600 Series SIP IP Deskphones will:
• Locate multiple controller addresses in priority order,
• Detect the availability of each controller,
• Transition automatically to lower priority controllers whenever a high priority controller fails or
becomes unreachable (automatic failover),
• Transition from lower priority controllers to a high priority controller (failback) either
automatically or as a result of explicit administrator activity,
• Preserve active calls to the greatest extent possible in the event of a transition, and
• Preserve as many call and system features as possible when operating under failure
conditions.
• Be in a pushable state during transition, when the primary controller is lost and the deskphone
is not connected to a secondary controller. Once the phone is registered on secondary
controller (AudioCodes, Cisco, etc.) and regardless if the phone is active on a call, the phone is
in a pushable state, just as if were connected to primary server. The phone is always in a
pushable for state for all normal or barge-in Top Line. Display, Audio Receive/Transmit, or
phonexml pushes for all transition conditions.
In general, the phone does not attempt to preserve SIP transactions in progress when a controller
failure is detected, and some mid-call features like conferencing can fail. However, in some
scenarios the same transaction may succeed if re-attempted once the transition to a new controller
has been completed.
The deskphone always registers to a configured controller with the credentials (username/
password) of the user who is currently logged-in, even if the deskphone transitions from one
controller to another.
As described in the respective deskphone user guide, certain features may not be available and
functionality may be limited or work differently during any stage of failover, "limbo," transition, or
failback. Calls can still be placed and received, and other deskphone functions remain active. The
following apply when a deskphone is in failover mode:
• If the user is active on a call, a failover icon displays when failing over to a non-AST controller
and messages like "Link recovery." "Limited phone service." and "Calls may be lost." inform the
user of a failover situation. The message "Limited phone service" also displays during failover
transition from one Session Manager server to another when the subscriptions have not yet
Administering Avaya 9601/9608/9611G/9621G/9641G/9641GS IP Deskphones SIP
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on page 131
Comments on this document? infodev@avaya.com
August 2015