The PCRF may subscribe to an event trigger on the node. The PCRF subscribes to new event triggers or removes armed event triggers unsolicited at any time. When an event matching the event trigger occurs, the node reports the event to the PCRF. The event triggers that are required in procedures are unconditionally reported (for example, IP address allocation/de-allocation) from the node, while the PCRF may subscribe to the remaining events (for example Usage-Monitoring).
When sent from the PCRF to the node, the Event Trigger AVP indicates an event that triggers an action in the node. When sent from the node to the PCRF, the Event Trigger AVP indicates that the corresponding event has occurred. If no Event Trigger AVP is included in a CCA or RAR operation, any previously provisioned event trigger is still applicable.
The PCRF may remove all previously provided event triggers by providing the Event-Trigger AVP set to the value NO_EVENT_TRIGGERS. When an Event-Trigger AVP is provided with this value, no other Event-Trigger AVP is provided in the cca or rar command. Upon reception of an Event-Trigger AVP with this value, the node does not inform the PCRF of any event except for those events that are always reported and do not require provisioning from the PCRF.
When the PCRF subscribes to one or more event triggers by using the rar command, the node sends the corresponding currently applicable values to the PCRF in the RAA if available, and in this case, the Event-Trigger AVPs are not included.
For a list of the supported events on the node, see the 7750 SR Gx AVPs Reference Guide.