CF, NEF, NSSF, SMSF, AUSF, CHF, NRF, NWDAF, I-CSCF, S-CSCF, IMS-AS, SCP, and UDM Nnrf NFDiscovery Request Request/Response AMF, SMF, PCF, NEF, NSSF, SMSF, AUSF, CHF, NRF, NWDAF, I-CSCF, S-CSCF, IMS-AS, SCP, UDM, and AF Nnrf_AccessToken Request/Response AMF, SMF, PCF, NEF, NSSF, SMSF, AUSF, UDM, NWDAF, I-CSCF, S-CSCF, IMS-AS, and HSS Figure 3.20 - Services offered by the NRF REST in 5G AF services The Naf_EventExposure service offered by the AF enables the consumer network function to subscribe for notifications of events. The consumer can be notified about the following events: Service experience information Performance data information UE mobility information UE communication information Service Name Service Operations Operation Sematics Consumer Naf_EventExposure Subscribe Subscribe/Notify NEF and NWDAF Unsubscribe NEF and NWDAF Notify NEF and NWDAF Naf_ProSe AuthorizeDiscovery Request/Response 5G DDNMF Figure 3.21- - Services offered by the AF The Naf_ProSe service enables the consumer to request authorization for discovery requests. Network Slice Selection Function (NSSF) services The NSSF offers a set of services to its consumers. The list of the services offered is as follows, per 3GPP Release 16, 23.502. Service Name Service Operations Operation Consumers Nnssf_NSSelection Request/Response AMF, NSSF in a different PLMN, SMF and NWDAF (Nnssf_NSSAIAvaillability Update Request/Response Subscribe Subscribe/Notify Unsubscribe Notify Delete Request/Response Nnssf_NSRestriction Subscribe Subscribe/Notify Notify Figure 3.22 - Services offered by the NSSF Lets take a deep dive into each of these services provided by the NSSF: The (NnssfNSSelection service is used to support network slice selection. The requesting NF is the AMF in this case, and the NSSF provides to the AMF the allowed NSSAI and configured NSSAI for the serving PLMN. Building Blocks - Cloud Native Infrastructure The Nnssf_NSSAIAvailability service is for the AMF to inform the NSSF about the S-NSSAIs (the S-NSSAI is used to uniquely identify a networ