5.21.3.4 Reliability of NF Services

When multiple NF Service instances within a NF Service Set are exposed to the NF Service consumer or SCP and the failure of NF Service instance is detected or notified by the NRF, i.e. it is not available anymore, the NF Service consumer or SCP selects another NF Service instance of the same NF Service Set within the NF instance, if available. Otherwise the NF Service consumer or SCP selects a different NF instance within the same NF Set. The NF service consumer or SCP may also take the above action based on notification of subscription of signalling storm analytics from NWDAF.

NOTE: The NF Producer instance can change the NF Service instance in the response to the service request.

When multiple NF Service instances within a NF Service Set are exposed to the NF Service consumer or SCP as a single NF Service, the reliability, i.e. the selection of an alternative NF Service instance is handled within the NF instance.