If a 5G-S-TMSI or GUAMI
is not included or the 5G-S-TMSI or GUAMI
does not indicate a valid AMF the (R)AN, based on (R)AT and Requested NSSAI, if available, selects an AMF.
The (R)AN selects an AMF as described in TS 23.501 , clause 6.3.5
. If UE is in CM-CONNECTED state, the (R)AN can forward the Registration Request message to the AMF based on the N2 connection of the UE.
If the (R)AN cannot select an appropriate AMF, it forwards the Registration Request to an AMF which has been configured, in (R)AN, to perform AMF selection.