4.7 Spending limits Procedures over Sy reference point

29.2133GPPPolicy and charging control signalling flows and Quality of Service (QoS) parameter mappingRelease 17TS

4.7.1 Initial Spending Limit Report Request

In the following procedure, the signalling flow for the H-PCRF to request the status of the policy counters available at the OCS, and to subscribe to updates of these policy counters by the OCS. If the H-PCRF provides the list of policy counter identifier(s), the OCS returns the policy counter status per policy counter identifier provided by the PCRF. If the H-PCRF does not provide the list of policy counter identifier(s), the OCS returns the policy counter status for all policy counter identifier(s), which are available for this subscriber.

Figure 4.7.1: Initial Spending Limit Report Request

1. The H-PCRF retrieves subscription information that indicates that policy decisions depend on policy counter(s) held at the OCS and optionally the list of policy counter identifier(s).

2. The H-PCRF sends a Diameter SLR command if no Sy session yet has been established for this subscriber. The Diameter SLR command includes the Subscription-Id AVP (e.g. IMSI) and optionally the list of policy counter identifier(s) within Policy-Counter-Identifier AVPs. The request also includes the SL-Request-Type AVP which set to the value INITIAL_REQUEST (0).

3. The OCS sends a Diameter SLA command to the PCRF. The Diameter SLA includes a Policy-Counter-Status-Report AVP for each requested policy counter identifier containing the policy counter identifier and the current status value, optionally pending policy counter statuses with the activation times, and Result-Code AVP contains the result of the operation. When no policy counter identifier(s) was provided, the Diameter SLA includes a Policy-Counter-Status-Report AVP for all policy counter identifiers applicable to the subscriber. The OCS stores the H-PCRF’s subscription to changes in the status of all policy counter identifiers provided to the H-PCRF in the Diameter SLA.

4.7.2 Intermediate Spending Limit Report Request

This clause describes the signalling flow for the H-PCRF to request the status of additional policy counters available at the OCS or to remove the request for the status of policy counters available at OCS. If the H-PCRF provides the list of policy counter identifier(s), the OCS returns the policy counter status per policy counter identifier provided by the PCRF.

Figure 4.7.2: Intermediate Spending Limit Report Request

1. The H-PCRF decides to modify the list of subscribed policy counters, e.g. PCRF determines that policy decisions depend on additional policy counter identifier(s) held at the OCS or that notifications of policy counter status changes for some policy counters are no longer required.

2. The H-PCRF sends a Diameter SLR command, optionally including the list of policy counter identifier(s) within Policy-Counter-Identifier(s) AVPs. The request also includes the SL-Request-Type AVP which set to the value INTERMEDIATE_REQUEST (1).

3. The OCS sends the Diameter SLA command to the PCRF including Policy-Counter-Status-Report AVP(s) containing the policy counter identifier, the current status value and optionally pending policy counter statuses with the activation times. Result-Code contains the result of the operation is also included in the response.

4. The PCRF makes the policy decision based on the information provided by the OCS.

4.7.3 Final Spending Limit Report Request

This clause describes the signalling flow for the H-PCRF to unsubscribe to any future updates of policy counters for a given subscriber by the OCS. It cancels the request for reporting the change of the status of the policy counters available at the OCS.

Figure 4.7.3: Final Spending Limit Report Request

1. The PCRF decides that policy decisions for a given user no longer depend on policy counter(s) to which the PCRF has existing subscriptions for status change notification.

2. The H-PCRF sends the Diameter STR command to the OCS to cancel the notification request from the OCS on policy counter status. The request includes the Termination-Cause which contains the reason why the session was terminated set to “DIAMETER_LOGOUT”.

3. The OCS sends the Diameter STA command to the H-PCRF with Result-Code contains the result of the operation.

4.7.4 Spending Limit Report

This clause describes the signalling flow for the OCS to notify the changes of the status of a subscribed policy counter(s) available at the OCS for that subscriber. Alternatively, the signalling flow can be re-used by the OCS to provide one or more pending statuses for a subscribed policy counter together with the time that have to be applied.

Figure 4.7.4: Spending Limit Report

1. The OCS detects that status of a policy counter identifier(s) has changed and the PCRF requested notification of changes in the status of a policy counter(s). Alternatively, if the OCS detects a policy counter status will change at a future point in time, the OCS shall be able to instruct the PCRF to apply one or more pending statuses for a requested policy counter.

2. When the status of a specific policy counter changes, or the OCS detects that a policy counter status will change at a future point in time and decides to instruct the PCRF to apply one or more pending statuses for a requested policy counter, the OCS shall determine the Sy sessions impacted by the change (i.e. those Sy sessions that have subscribed to status change notifications for the changed policy counter) and send the Diameter SNR command to the PCRF associated with each affected Sy session including one Policy-Counter-Status-Report AVP. If several counters change status at the same time, the OCS may group the status change notifications into a single Spending Limit Report request to the PCRF by sending multiple Policy-Counter-Status-Report AVPs in the request.

NOTE: Sy session is per UE. And more than one Sy session will exist when the UE has IP-CAN session connection with more than one PCRF.

3. The H-PCRF acknowledges the request by sending a Diameter SNA command with a Result-Code AVP set to DIAMETER_SUCCESS and use the status of the received policy counter(s) as input to its policy decision to apply operator defined actions, e.g. downgrade the QoS. The PCRF shall ignore an unknown policy counter status report for all unknown policy counter identifiers in the SNR from the OCS.