5.15.8 Configuration of Network Slice support and availability in a PLMN

A Network Slice may be supported in the whole PLMN or in one or more Tracking Areas of the PLMN. A Network Slice is supported within a TA if the 5G-AN has been configured to support the S-NSSAI in the TA.

Network Slices are defined to be available within an NS-AoS when the Network Slice is supported in the set of TAs which the NS-AoS comprises and more than zero resources are allocated to the Network Slice in the NG-RAN cells of the NS-AoS. An NS-AoS can be defined on a per cell level granularity when the NS-AoS is not matching deployed Tracking Areas as defined in clause 5.15.18.

The availability of a Network Slice S-NSSAI in an NS-AoS requires the support of the S-NSSAI in the involved NFs and in the NG-RAN in the TAs which the NS-AoS comprises. Hence, the cells of a TA need to be configured to support a S-NSSAI if the S-NSSAI needs to be available in at least a cell of the TA. A Network Slice is considered available in a TA if the Network Slice is supported within the TA and available in all cells of the TA. 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 [34]) and TS 38.300 [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 [34] and TS 38.300 [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.