Section: 5.30.2.8 Access to stand-alone non-public network services via PLMN
Content: To access SNPN services, a UE that has successfully registered with a PLMN over 3GPP access may perform another registration via the PLMN User Plane with an SNPN (using the credentials of that SNPN) following the same architectural principles as specified in clause 4.2.8 (including the optional support for PDU Session continuity between PLMN and SNPN using the Handover of a PDU Session procedures in clauses 4.9.2.1 and 4.9.2.2 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]) and the PLMN taking the role of "Untrusted non-3GPP access" of the SNPN, i.e. using the procedures for Untrusted non-3GPP access in clause 4.12.2 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]. Annex D, clause D.3 provides additional details. The case where UE that has successfully registered with a PLMN over non-3GPP access to access SNPN services is not specified in this Release. NOTE: QoS differentiation in the PLMN can be provided on per-IPsec Child Security Association basis by using the UE or network requested PDU Session Modification procedure described in clause 4.3.3.2 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]. In the SNPN, N3IWF determines the IPsec child SAs as defined in clause 4.12 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]. The N3IWF is preconfigured by SNPN to allocate different IPsec child SAs for QoS Flows with different QoS profiles. To support QoS differentiation in the PLMN with network-initiated QoS, the mapping rules between the PLMN and the SNPN are assumed to be governed by an SLA including: 1) mapping between the DSCP markings for the IPsec child SAs on NWu and the corresponding QoS, which is the QoS requirement of the SNPN and is expected to be provided by the PLMN, and 2) N3IWF IP address(es) in the SNPN. The non-alteration of the DSCP field on NWu is also assumed to be governed by an SLA and by transport-level arrangements that are outside of 3GPP scope. The packet detection filters in the PLMN can be based on the N3IWF IP address and the DSCP markings on NWu. To support QoS differentiation in the PLMN with UE-requested QoS, the UE can request for an IPsec SA the same 5QI from the PLMN as the 5QI provided by the SNPN. It is assumed that UE-requested QoS is used only when the 5QIs used by the SNPN are from the range of standardized 5QIs. The packet filters in the requested QoS rule can be based on the N3IWF IP address and the SPI associated with the IPsec SA. Refer to clause D.7 for details on how to support QoS differentiation. When the UE accesses the SNPN over NWu via a PLMN, the AMF in the SNPN shall send an indication toward the UE during the Registration procedure to indicate whether an IMS voice over PS session is supported or not.