Section: 5.16.3.11 P-CSCF discovery and selection
Content: P-CSCF selection functionality may be used by the SMF to select the P-CSCF for an IMS PDU Session of the UE. The SMF can utilize the Network Repository Function to discover the P-CSCF instance(s). The NRF provides the IP address or the FQDN of P-CSCF instance(s) to the SMF. The P-CSCF selection function in the SMF selects the P-CSCF instance(s) based on the available P-CSCF instances obtained from NRF or based on the configured P-CSCF information in the SMF. If the SMF receives FQDN(s) from the NRF or is configured with FQDN(s) the SMF shall resolve these to IP addresses for sending to the UE in the PDU session response. The following factors may be considered during the P-CSCF discovery and selection: - S-NSSAI of the PDU Session. - UE location information. - Local operator policies. - Availability of candidate P-CSCFs. - UE IP address. - Access Type. - Proximity to location of selected UPF. - Selected Data Network Name (DNN).