Ast Feature Determination - Avaya 9601 Administering

System Failover and Survivability
3. Controller Failover - The deskphone removes all the existing subscriptions and establishes
subscriptions with the highest priority controller that is available.
4. Controller Failback - If the failback policy is "auto" or if the failback policy is "admin" and the
trigger is a message, the deskphone unsubscribes from the current controller and subscribes
with the highest priority controller available. Otherwise (for example, the failback policy is
"admin" and the trigger is Trigger 1 or Trigger 2), the deskphone executes a "controller
subscription refresh."
When one of the triggers occurs, the deskphone follows this algorithm:
1. If there is no active call, the controller search is performed immediately.
• If the current controller is available and it is the highest priority available controller, the
"Controller Subscription Refresh" function is performed.
• If the current controller is available, but there is a higher priority controller available, the
"Controller Failback" function is performed.
• If the current controller is not available, the "Controller Failover" function is performed.
2. If there is an active call, the controller search (Step 1) is performed when the call is over.
Related Links
Controller Determination and Survivability Activity

AST feature determination

After the Active controller has been selected, the deskphone examines the value of the
DISCOVER_AVAYA_ENVIRONMENT parameter.
If the parameter value is 1, the phone determines if that controller supports the AST (Advanced SIP
Telephony) feature set or not. The phone sends a SUBSCRIBE request to the active controller for
the "Feature Status Event Package" (avaya-cm-feature-status). If the request succeeds, the phone
proceeds with PPM Synchronization. If the request is either rejected, is proxied back to the phone,
or does not receive a response, the deskphone assumes that AST features are not available.
If the parameter value is 0, the deskphone operates in a mode where AST features are not
available.
Upon receiving a 202 Pending response, the deskphone starts an internal timer of 16 seconds and
waits to receive a NOTIFY to determine whether the subscription is active or terminated. If the
NOTIFY indicates an "active" state, the phone considers itself in an AST environment and proceeds
with PPM Synchronization. If the NOTIFY indicates a "terminated" state, the phone considers itself
in a non-AST environment. It periodically retries the subscription to the Feature Status Event
Package. If it receives a 202 Pending response, it continues as specified above. If the 16 second
timer expires before a NOTIFY is received the phone considers itself in a non-AST environment.
Related Links
Controller Determination and Survivability Activity
Administering Avaya 9601/9608/9611G/9621G/9641G/9641GS IP Deskphones SIP
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Comments on this document? infodev@avaya.com
August 2015