4.8 Call flows for User Plane Congestion Management

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

4.8.1 General

The call flows for User Plane Congestion Management (UPCON) over Np reference point are specified as follows:

– RAN User Plane Congestion Information (RUCI) reporting, in which non-aggregated RUCI reporting and aggregated RUCI reporting are included.

– Reporting restriction provisioning

– UE mobility between RAN Congestion Awareness Functions (RCAFs)

– Removal of UE context

4.8.2 RUCI reporting

4.8.2.1 Non-aggregated RUCI report procedure

Figure 4.8.2.1.1: Non-aggregated RUCI reporting

1. The RCAF sends a diameter NR-Request command to the PCRF, including the user id, PDN ID, the congestion level info and additional parameters as defined in clause 4.4.1.2 of 3GPP TS 29.217 [36].

2. The PCRF stores the related information and acknowledges the RUCI reporting by sending a Diameter NR-Answer including the PCRF id.

4.8.2.2 Aggregated RUCI report procedure

Figure 4.8.2.2.1: Aggregated RUCI reporting

1. The RCAF sends a Diameter AR-Request command to the PCRF, including one or more Aggregated-RUCI-Report AVP and additional parameters as defined in clause 4.4.1.3 of 3GPP TS 29.217 [36]. The PCRF is the common destination PCRF for a set of user id and PDN ID and identified by the PCRF id returned in the previous non-aggregating RUCI reporting.

2. The PCRF stores the related information and acknowledges the RUCI reporting by sending a Diameter AR-Answer back to the RCAF.

4.8.3 Np reporting restriction provisioning

The Np reporting restriction provisioning is used by the PCRF to stop RUCI reporting for a specific user id and PDN ID. It is also used by the PCRF to specify, modify or disable restrictions for RUCI reporting.

Figure 4.8.3.1: Np reporting restriction provisioning

1. The PCRF sends a Diameter MUR command to the RCAF for the provisioning of RUCI reporting restriction including the parameters as defined in clause 4.4.2 of 3GPP TS 29.217 [36].

2. The RCAF responds a Diameter MUA command to the PCRF including the parameters as defined in clause 4.4.2 of 3GPP TS 29.217 [36].

4.8.4 UE mobility between RCAFs

This signalling flow describes the mobility handling of a UE from one RCAF to another RCAF. The UE is affected by congestion for both RCAFs.

Figure 4.8.4.1: UE mobility from RCAF1 to RCAF2 (the UE is affected by congestion at RCAF2 after the UE was earlier affected by congestion at RCAF1)

1. The UE is located in the RCAF1 which is affected by congestion. The RCAF1 sends a Diameter NRR command to the PCRF for reporting RUCI including the parameters as defined in clause 4.4.1.2 of 3GPP TS 29.217 [36].

2. The PCRF stores the identity of RCAF1 for the given UE and responds a Diameter NRA command to the RCAF1 including the parameters as defined in clause 4.4.1.2 of 3GPP TS 29.217 [36].

3. The UE moves to the RCAF2 which is also affected by congestion. The RCAF2 sends a Diameter NRR command to the PCRF for reporting RUCI of the same UE including the parameters as defined in clause 4.4.1.2 of 3GPP TS 29.217 [36].

4. The PCRF stores the identity of RCAF2 for the given UE and responds a Diameter NRA command to the RCAF2 including the parameters as defined in clause 4.4.1.2 of 3GPP TS 29.217 [36].

5. The PCRF initiates a removal of the UE context to RCAF1 to release the context of the given user id and PDN ID, including the parameters as defined in clause 4.4.4 of 3GPP TS 29.217 [36].

4.8.5 Removal of UE context

This signalling flow describes the removal of a UE context from the RCAF.

Figure 4.8.5.1: UE context removal in RCAF

1. The PCRF sends a Diameter MUR command to the RCAF to release the context of the given user id and PDN ID, including the parameters as defined in clause 4.4.4 of 3GPP TS 29.217 [36].

2. The RCAF responds with a Diameter MUA command to the PCRF including the parameters as defined in clause 4.4.4 of 3GPP TS 29.217 [36]. The RCAF releases the context corresponding to the given user id and PDN ID, including any reporting restriction.