The node reports usage information to the PCRF under the following conditions:
when a usage threshold is reached
when all pcc rules associated with the monitoring are removed or deactivated
when Usage-Monitoring is explicitly disabled by PCRF
when a session is terminated
when requested by PCRF (on demand)
To report accumulated usage for a specific monitoring-key, the node sends a CCR with the Usage-Monitoring-Information AVP containing the accumulated usage information since the last report. For each of the enabled monitoring-keys, the Usage-Monitoring-Information AVP includes the Monitoring-Key AVP and the accumulated volume usage in the Used-Service-Unit AVP.
A usage report on the node can be triggered by reaching the usage threshold communicated to the node by the PCRF in the CCR-U message carrying accumulated usage for that monitoring entity along with the Event-Trigger AVP set to USAGE_REPORT.
In response to the CCR-U message, the PCRF communicates to the node via a CCA-u message whether the Usage-Monitoring should continue:
If the new thresholds for the currently monitored entity/levels are provided in Granted-Service-Units AVP, the Usage-Monitoring continues.
If the thresholds are not included in Granted-Service-Units AVP, the Usage-Monitoring stops.
Thresholds are incremental. For example, if the quota of 100 MB is submitted to the node, the usage should be reported when that quota is reached. At that point, the user can be granted another 100 MB. The new usage report on the node is triggered when another 100 MB are accumulated. Absence of the threshold for an entity in the CCA-u message is an indication that the Usage-Monitoring should stop.
When the PCRF informs the node that Usage-Monitoring should stop (by not including thresholds in CCA-u), the node does not report usage which has accumulated between sending the CCR and receiving the CCA.
Another possibility of usage reporting is on-demand. In this scenario, usage for one or more monitoring keys is reported whether the usage threshold has been reached. This is achieved by sending the node the Usage-Monitoring-Report AVP (within the Usage-Monitoring-Information AVP) set to USAGE-MONITORING_REPORT_REQUIRED. If the Monitoring-Key AVP is omitted in such a request, Usage-Monitoring for all enabled entities is reported to the PCRF.
If that the credit-category is removed from the subscriber host (the sla-profile instance referencing the category-map is changed for the subscriber host), the node reports the outstanding usage in a CCR-U message with the Event-Trigger set to USAGE_REPORT.