B.17 Handling of MPS Session

29.5143GPP5G SystemPolicy Authorization ServiceRelease 18Stage 3TS

When the P-CSCF receives an authorised Resource-Priority header field or when the P-CSCF adds a temporarily authorised Resource-Priority header field containing an appropriate namespace and priority value in SIP signaling, and recognizes the need for priority treatment as specified in 3GPP TS 24.229 [32], and the "IMS_SBI" feature is supported, the P-CSCF shall include the "mpsId" attribute and the "resPrio" attribute in the corresponding Npcf_PolicyAuthorization service operation towards the PCF. The "mpsId" attribute shall contain the national variant for MPS service name indicating an MPS session. The "resPrio" attribute shall be determined based on the resource value received in the "wps" namespace of the SIP Resource-Priority header field, and shall be included at "AppSessionContextReqData" data type level as well as the "MediaComponent" data type level. The "resPrio" attribute shall be populated with a default value if the priority value is unknown.

NOTE 1: Various mechanisms can be applied to recognize the need for priority treatment in the P-CSCF (e.g., based on the dialled digits), according to national regulation and network configuration, as stated in 3GPP TS 24.229 [32].

NOTE 2: Highest user priority level (lowest numerical resource value of the SIP Resource-Priority header field) is mapped to the highest enumerated value of the "resPrio" attribute.

If the P-CSCF supports the SBI Message Priority mechanism for an MPS session, the P-CSCF shall include the "3gpp-Sbi-Message-Priority" custom HTTP header with a priority value based on the value of the "resPrio" attribute. The highest "resPrio" value is mapped to the corresponding lowest value of the "3gpp-Sbi-Message-Priority" custom HTTP header.

Upon reception of a request that requires MPS treatment, the PCF shall derive the PCC rules corresponding to the MPS session, as appropriate. The PCF shall take specific actions on the corresponding PDU session to ensure that the MPS session is prioritized, as described in 3GPP TS 29.512 [8], clause 4.2.6.2.12.3.

When the P-CSCF detects that the MPS session has ended, the P-CSCF deletes in the PCF the "Individual Application Session Context" resource corresponding to the MPS session. The PCF shall delete the PCC rules corresponding to the MPS session and shall revoke the actions related to the prioritization of the MPS session in the corresponding PDU session, as described in 3GPP TS 29.512 [8], clause 4.2.6.2.12.3.

Annex C (normative):
Flow identifiers: Format definition and examples