Section: 5.15.12 Support of subscription-based restrictions to simultaneous registration of network slices 5.15.12.1 General
Content: The subscription information for a UE may include for each S-NSSAI Network Slice Simultaneous Registration Group (NSSRG) information constraining which S-NSSAIs can be simultaneously provided to the UE in the Allowed NSSAI. When S-NSSAIs have associated NSSRG information, then the S-NSSAIs in the Allowed NSSAI shall share at least one NSSRG. The NSSRG information, defining the association of S-NSSAIs to NSSRG, is provided as an additional and separate information. If the optional NSSRG information is not present for the S-NSSAIs of a subscription, and other restrictions do not apply e.g. availability at a specific location, then it is assumed that all the S-NSSAIs in the subscription information can be simultaneously provided to the UE in the Allowed NSSAI. However, if NSSRG information is present in the subscription information, at least one NSSRG shall be associated with each of the S-NSSAIs in the subscription information. At any time, if the AMF has received subscription information for a UE that includes NSSRG information, the Allowed NSSAI for the UE can only include S-NSSAIs which share a common NSSRG. NOTE 1: The AMF enforces NSSRG only for the access(es) the UE registered to the AMF. When the UE is registered to different PLMNs over 3GPP access and non-3GPP access, the AMF in one access cannot enforce a common NSSRG over both accesses. The default S-NSSAIs, if more than one is present, are associated with the same NSSRGs, i.e. the UE is always allowed to be registered with all the default S-NSSAIs simultaneously. The HPLMN only sends S-NSSAIs sharing all the NSSRGs of the Default S-NSSAIs to a non-supporting VPLMN as part of the subscription information, i.e. in addition to the default S-NSSAI(s), the HPLMN may send any other subscribed S-NSSAI which shares at least all the NSSRG defined for the default S-NSSAI(s), and the HPLMN sends no NSSRG information to the VPLMN. A subscription information that includes NSSRG information shall include at least one default S-NSSAI. A supporting AMF/NSSF, when it receives a Requested NSSAI, evaluates the S-NSSAIs of the HPLMN (in the mapping information of the Requested NSSAI, when a mapping information is applicable) based on any received NSSRG information for these S-NSSAIs, to determines whether they can be provided together in the Allowed NSSAI. NOTE 2: An HPLMN enabling support of subscription-based restrictions to simultaneous registration of network slices for a Subscriber, can set the subscribed S-NSSAI(s) already in the subscription information before the NSSRG information was added to the subscription information, to have the same NSSRGs defined for the default S-NSSAI(s) if it has to continue to support the same service behaviour for these S-NSSAIs.