6.17 APN information retrieval procedure

23.0603GPPGeneral Packet Radio Service (GPRS)Release 17Service descriptionStage 2TS

This procedure is used by the RCAF to retrieve the APNs of the active PDN connections of the UEs served by a specific (congested) UTRAN cell. The RCAF leverages this information to determine the PCRFs serving these UEs and subsequently report RAN user-plane congestion information (RUCI) to the PCRFs.

NOTE 1: The details of congestion reporting to the PCRF are specified in TS 23.203 [88].

The RCAF determines the SGSNs that are serving the congested UTRAN cell based on the Routing Area Identities served by the congested UTRAN cell. For further details on the related DNS procedure see TS 29.303 [100]. The following steps are applied for all SGSNs serving the congested UTRAN cell.

NOTE 2: In network sharing scenarios the RCAF belongs to the RAN operator. In this case it is up to inter-operator agreements and operator configuration which sharing partner’s SGSNs the RCAF queries APN information from.

Figure 6.17-1: APN information retrieval procedure

1. The RCAF sends an APN information request to the SGSN. The request shall include the IMSIs for which the RCAF wants to retrieve APN information.

2. The SGSN sends the APN information response to the RCAF. The response shall contain the the list of APNs of the active PDN connections of each IMSI.

NOTE 3: In order for RCAF to maintain the APN information for UEs in a congested cell, the RCAF needs to regularly receive APN information updates from the SGSN. The details of whether the RCAF needs to query the SGSN regularly or whether the SGSN updates the RCAF regularly without further explicit requests from the RCAF is defined in Stage 3.