Ast Feature Determination; Ppm Synchronization - Avaya 9608 Administrator's Manual

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.

4. 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.

5. PPM synchronization

As part of PPM synchronization the deskphone performs a getAllEndpointConfiguration
request. This request contains the following EndpointConfigurationFields:
VolumeSettings
●
LinePreferenceInfo
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Controller Determination and Survivability Activity
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