6.3.22 NSACF discovery and selection

The NF consumers shall utilise the NRF to discover NSACF instance(s), including the NSACF acting as Primary NSACF role, unless NSACF information is available by other means, e.g. locally configured in NF consumers.

The NSACF selection function in the NSACF NF consumer selects an NSACF instance based on the available NSACF instances, which are obtained from the NRF or locally configured in the NSACF NF consumer.

The following factors may be considered by the NF consumer for NSACF discovery and selection:

• S-NSSAI(s).
• NSAC Service Area Identifier, or a reserved value "Entire PLMN" for discovering the NSACF acting as Primary NSACF or centralized NSAC role. The NSAC Service Area Identifier is configured at the consumer NF and NSACF (see clause 5.15.11.0). Each Service Area Identifier is a unique and unambiguous identifier and a NSACF registers with the NRF the NSAC Service Area Identifier(s) of the NSAC Service Area(s) it serves. "Entire PLMN" is indicated in roaming case to the NRF of HPLMN by the VPLMN NF consumer when the VPLMN NF consumer needs to discover the HPLMN NSACF, or in non roaming case to select a Primary NSACF.
• NSACF service capabilities:
• Support monitoring and controlling the number of registered UEs per network slice for the network slice that is subject to NSAC.
• Support, for network slices that are subject to NSAC and configured to support EPS counting, monitoring and controlling the number of registered UEs with at least one PDU session per network slice, as defined in clause 5.15.11.5a.
• Support monitoring and controlling the number of established PDU Sessions per network slice for the network slice that is subject to NSAC.
• PLMN ID information in the case of roaming to contact the HPLMN NSACF for inbound roamers.

In the case of delegated discovery and selection in SCP, the NSACF NF consumer shall send all available and applicable factors to the SCP.