Step 1.
The AMF establishes an AM Policy Association for retrieving access and mobility related policy information, e.g. RFSP index value, as described in
clause 4.16.1.2.
Step 2.
If the access and mobility related policy information depends on the application in use, then depending on operator policies in the PCF, the PCF may subscribe to the BSF, then step 3 follows, or provides its PCF binding information to the AMF in step 1 with the indication to be notified about the PCF for the PDU Session for a DNN, S-NSSAI, then step 4 follows.
Step 3.
The PCF for the UE determines that access and mobility related policy information (e.g. RFSP index value) depends on the detection of one or more application(s) in use, the DNN, S-NSSAI used to access each Application Id is configured in the PCF or retrieved from the UDR as part of the Application Data Set, then subscribes to the BSF to be notified when a PCF for the PDU Session for this SUPI is registered in the BSF, by invoking Nbsf_Management_Subscribe (SUPI, list of (DNN, S-NSSAI)(s)). Steps 4 and 5 are repeated for each PCF registered for a PDU Session to a (DNN, S-NSSAI) included in the Nbsf_Management.
Step 4.
The SMF establishes a SM Policy Association as described in
clause 4.16.4. The allocated UE address/prefix, SUPI, DNN, S-NSSAI and the PCF address is registered in the BSF, as described in
clause 6.1.1.2.2 of TS 23.503.
Step 5a.
If the PCF for the UE subscribed to the BSF, then the BSF notifies that a PCF for the PDU Session is registered in the BSF, by invoking Nbsf_Management_Notify (DNN, S-NSSAI, UE address(es), PCF address, PCF instance id, PCF Set ID, level of binding). When there are multiple PDU Sessions to the same (DNN, S-NSSAI) the BSF provides multiple notification to the PCF.
Step 5b.
If the PCF for the UE sent the request to notify that a PCF for the PDU Session is available to the AMF in step 1, then the PCF for the PDU Sessions sends Npcf_PolicyAuthorization_Notify (EventID set to SM Policy Association established, UE address, PCF address, PCF instance is, PCF Set ID) to the PCF indicated in the PCF binding information provided by the SMF.
Step 6.
The PCF for the UE subscribes to notifications of event
"start/stop of application traffic" as defined in
clause 6.1.3.18 of TS 23.503, using
Npcf_PolicyAuthorization_Subscribe (UE address, EventId, EventFilter set to
"list of Application Identifiers") to the PCF for the PDU Session to the DNN, S-NSSAI. The PCF for the PDU Session then generates PCC Rules including the Application Identifier in the SDF template, if there are multiple Application Identifiers included in the
Npcf_PolicyAuthorization, the PCF generates PCC Rules for each Application Identifier. The response includes the NotificationCorrelationId.
Step 7.
The PCF installs PCC Rules and the Policy Control Request Trigger to detect "start/stop of application traffic" in the SMF.
Step 8.
The SMF detects that the Policy Control Request Trigger is met, then reports the start/stop of application traffic to the PCF serving the PDU Session.
Step 9.
The PCF for the UE is notified on the start/stop of application traffic by Npcf_PolicyAuthorization_Notify (NotificationCorrelationId, EventId set to "start/stop of application traffic", EventInformation including the ApplicationId). When the reporting of start and stop of a list of Application(s) was requested, the PCF for the PDU Session provides multiple notification to the PCF for the UE.
Step 10.
The PCF checks operator policies and then may change access and mobility related policy information (e.g. RFSP index value) based on the reporting of start/stop of application traffic.
Step 11.
The SM Policy Association is terminated as described in
clause 4.16.6. The allocated UE address/prefix, SUPI, DNN, S-NSSAI and the PCF address are deregistered in the BSF.
Step 12a.
If the PCF for the UE subscribed to the BSF, then the BSF notifies that the PCF serving a PDU Session is deregistered in the BSF, by invoking Nbsf_Management_Notify (Binding Identifier for the PDU Session).
Step 12b.
If the PCF for the UE sent the request to notify that a PCF for the PDU Session is available to the AMF in step 1, then the PCF for the PDU Session sends Npcf_PolicyAuthoritation_Notify ((EventID set to SM Policy Association termination, Notification Correlation Id).