The AUSF shall execute authentication of the UE.
The authentication is performed as described in TS 33.501 
, by Nudm_UEAuthenticate_Get operation. The AUSF discovers a UDM as described in TS 23.501 , clause 6.3.8
. In case the AMF provided a SUCI
to AUSF, the AUSF shall return the SUPI
to AMF only after the authentication is successful.
If network slicing is used, the AMF decides if the Registration Request needs to be rerouted as described in clause 188.8.131.52.3
, where the initial AMF refers to the AMF.