Section: 5.15.8 Configuration of Network Slice availability in a PLMN
Content: A Network Slice may be supported in the whole PLMN or in one or more Tracking Areas of the PLMN. Network Slices may also be available with an NS-AoS not matching deployed Tracking Areas as defined in clause 5.15.18. The availability of a Network Slice refers to the support of the S-NSSAI in the involved NFs. In addition, policies in the NSSF may further restrict from using certain Network Slices in a particular TA, e.g. depending on the HPLMN of the UE. The UE can receive, for a Network Slice where the NS-AoS does not match the whole set of cells in one or more TAs, S-NSSAI location availability information as described in clause 5.15.18. The support of a Network Slice in a TA is established end-to-end using a combination of OAM and signalling among network functions. It is derived by using the S-NSSAIs supported per TA in 5G-AN, the S-NSSAIs supported in the AMF and operator policies per TA in the NSSF. The AMF learns the S-NSSAIs supported per TA by the 5G-AN when the 5G-AN nodes establish or update the N2 connection with the AMF (see TS 38.413[ NG-RAN; NG Application Protocol (NGAP) ]  [34]) and TS 38.300[ NR; NR and NG-RAN Overall description; Stage-2 ]  [27]). One or all AMF per AMF Set provides and updates the NSSF with the S-NSSAIs support per TA. The 5G-AN learns the S-NSSAIs per PLMN ID the AMFs it connects to support when the 5G-AN nodes establishes the N2 connection with the AMF or when the AMF updates the N2 connection with the 5G-AN (see TS 38.413[ NG-RAN; NG Application Protocol (NGAP) ]  [34] and TS 38.300[ NR; NR and NG-RAN Overall description; Stage-2 ]  [27]). The NSSF may be configured with operator policies specifying under what conditions the S-NSSAIs can be restricted per TA and per HPLMN of the UE. The per TA restricted S-NSSAIs may be provided to the AMFs of the AMF Sets at setup of the network and whenever changed. The AMF may be configured for the S-NSSAIs it supports with operator policies specifying any restriction per TA and per HPLMN of the UE.