To allow the 5G system to interwork with AFs related to existing services, e.g. IMS based services as described in TS 23.228
, Mission Critical Push To Talk services as described in TS 23.179
, the PCF shall support the corresponding IMS procedures defined in the main body of this TS via Rx interface. This facilitates the migration from EPC to 5GC without requiring these AFs to upgrade to support the Npcf_PolicyAuthorization
services in Rel-16.
Session Binding applies for PDU Sessions of IP type only.
The functionality described for Multimedia Priority Services (clause 126.96.36.199
) and Mission Critical service (clause 188.8.131.52
) applies via Rx interface.
In order to support IMS Emergency services over Rx interface, in addition to the functional description in clause 184.108.40.206
, the following applies: The PCF shall provide the IMEI and the subscriber identifiers (IMSI, MSISDN) (if available), received from the SMF at PDU Session establishment, if so requested by the P-CSCF. The PCF derives the IMEI from the PEI, the IMSI from the SUPI and the MSISDN from the GPSI.
Any AF using Rx, such as P-CSCF, the BSF determines the selected PCF address according to the information included in the incoming Rx requests and the information stored at the BSF. The BSF is able to proxy or redirect Rx requests targeting an IP address of a UE to the selected PCF.
The following event reporting is supported over Rx interface:
|Availability for Rx Session
|PLMN Identifier Notification
|The PLMN identifier where the UE is currently located.
|Change of Access Type
|The Access Type and, if applicable, the RAT Type of the PDU Session has changed.
|EPS fallback is initiated
|Signalling path status
|The status of the resources related to the signalling traffic of the AF session.
|Access Network Charging Correlation Information
|The Access Network Charging Correlation Information of the resources allocated for the AF session.
|Access Network Information Notification
|The user location and/or timezone when the PDU Session has changed in relation to the AF session.
|Reporting Usage for Sponsored Data Connectivity
|The usage threshold provided by the AF has been reached; or the AF session is terminated.
|Resource allocation status
|The status of the resources related to the AF session (established/released).
|QoS targets can no longer (or can again) be fulfilled
|The QoS targets can no longer (or can again) be fulfilled by the network for (a part of) the AF session.
|Out of credit
|Credit is no longer available.