5.16.3.4 P-CSCF address delivery

At PDU Session Establishment procedure related to IMS, SMF shall support the capability to send the P-CSCF address(es) to UE. The SMF is located in VPLMN if LBO is used. This is sent by visited SMF if LBO is used. For Home routed, this information is sent by the SMF in HPLMN. P-CSCF address(es) shall be sent transparently through AMF and in the case of Home Routed also through the SMF in VPLMN. The P-CSCF IP address(es) may be locally configured in the SMF, or discovered using NRF as described in clause 5.16.3.11.

NOTE 1: Other options to provide P-CSCF to the UE as defined in TS 23.228 [15] is not excluded.

NOTE 2: PDU Session for IMS is identified by "APN" or "DNN".

In the case of SNPN access the SMF is always located in the serving SNPN (no support for Home Routed traffic); therefore, the serving SMF sends the P-CSCF address(es) to the UE.