Section: 4.14.2 Stand-alone non-public network (SNPN)
Content: If the UE is not SNPN enabled, the UE is always considered to be not operating in SNPN access operation mode. If the UE is SNPN enabled, the UE can operate in SNPN access operation mode. Details of activation and deactivation of SNPN access operation mode at the SNPN-enabled UE are up to UE implementation. The functions and procedures of NAS described in the present document are applicable to an SNPN and an SNPN-enabled UE unless indicated otherwise. The key differences brought by the SNPN to the NAS layer are as follows: a) instead of the PLMN selection process, the SNPN selection process is performed by a UE operating in SNPN access operation mode (see 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [5] and 3GPP TS 24.502[ Access to the 3GPP 5G Core Network (5GCN) via non-3GPP access networks ]  [18] for further details on the SNPN selection); b) a "permanently forbidden SNPNs" list and a "temporarily forbidden SNPNs" list are managed per access type independently (i.e. 3GPP access or non-3GPP access) and, if the UE supports access to an SNPN using credentials from a credentials holder, equivalent SNPNs or both, per entry of the "list of subscriber data" or, if the UE supports access to an SNPN using credentials from a credentials holder, per the PLMN subscription, by a UE operating in SNPN access operation mode instead of forbidden PLMN lists. If the UE supports onboarding services in SNPN, an additional "permanently forbidden SNPNs" list for onboarding services and an additional "temporarily forbidden SNPNs" list for onboarding services are managed. If the UE supports access to an SNPN providing access for localized services in SNPN, an additional "permanently forbidden SNPNs for access for localized services in SNPN" list and an additional "temporarily forbidden SNPNs for access for localized services in SNPN" list per entry of the "list of subscriber data" and per the PLMN subscription are managed for 3GPP access only. These lists shall be maintained across activation and deactivation of SNPN access operation mode; NOTE 0: On timer T3245 expiry when the UE supports access to an SNPN using credentials from a credentials holder using PLMN subscription, and the UE is not operating in SNPN access operation mode, as an implementation option the UE can delete the list of "temporarily forbidden SNPNs" and "permanently forbidden SNPNs" and additionally the list of "permanently forbidden SNPNs for access for localized services in SNPN" and list of "temporarily forbidden SNPNs for access for localized services in SNPN" if the UE supports access to an SNPN providing access for localized services in SNPN. c) inter-system change to and from S1 mode is not supported; d) void; e) CAG is not supported in SNPN access operation mode; f) with respect to the 5GMM cause values: 1) 5GMM cause values #74 "Temporarily not authorized for this SNPN" and #75 "Permanently not authorized for this SNPN" are supported whereas these 5GMM cause values cannot be used in a PLMN; and 2) 5GMM cause values #11 "PLMN not allowed", #31 "Redirection to EPC required", #73 "Serving network not authorized", and #76 "Not authorized for this CAG or authorized for CAG cells only" are not supported whereas these 5GMM cause values can be used in a PLMN; g) a list of "5GS forbidden tracking areas for roaming" and a list of "5GS forbidden tracking areas for regional provision of service" are managed per SNPN and, if the UE supports access to an SNPN using credentials from a credentials holder, equivalent SNPNs or both, entry of the "list of subscriber data" or, if the UE supports access to an SNPN using credentials from a credentials holder,PLMN subscription (see 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [5]); h) when accessing SNPN services via a PLMN using 3GPP access, access to 5GCN of the SNPN is performed using 5GMM procedures for non-3GPP access, 5GMM parameters for non-3GPP access, the UE is performing access to SNPN over non-3GPP access and the UE is not operating in SNPN access operation mode over 3GPP access. When accessing PLMN services via a SNPN using 3GPP access, access to 5GCN of the PLMN is performed using 5GMM procedures for non-3GPP access, 5GMM parameters for non-3GPP access, the UE is not performing access to SNPN over non-3GPP access, and the UE is operating in SNPN access operation mode over 3GPP access. From the UE's NAS perspective, accessing PLMN services via an SNPN and accessing SNPN services via a PLMN are treated as untrusted non-3GPP access. If the UE is accessing the PLMN using non-3GPP access, the access to 5GCN of the SNPN via PLMN is not specified in this release of the specification . Emergency services are not supported in an SNPN when a UE accesses SNPN services via a PLMN; i) when registered to an SNPN, the UE shall use only the UE policies provided by the registered SNPN; j) inclusion of a TAI of an SNPN other than the registered SNPN, into the registration area is not supported. The AMF of an SNPN shall only include into the registration area one or more TAIs of the registered SNPN; j1) inclusion of a TAI of an SNPN other than the registered SNPN, into the LADN service area is not supported. The AMF of an SNPN shall only include one or more TAIs of the registered SNPN into the LADN service area; j2) inclusion of a TAI of an SNPN other than the registered SNPN, into the allowed area or the non-allowed area, of the 3GPP access service area restrictions is not supported. The AMF of an SNPN shall include only one or more TAIs of the registered SNPN into the allowed area or the non-allowed area, of the 3GPP access service area restrictions; k) void; l) void; m) UE mobility between SNPNs in 5GMM-CONNECTED mode is supported when the SNPNs are equivalent SNPNs for the selected entry of the "list of subscriber data" or the selected PLMN subscription. UE mobility between SNPNs in 5GMM-IDLE mode is supported when the UE supports access to an SNPN using credentials from a credentials holder or when the SNPNs are equivalent SNPNs or both for the selected entry of the "list of subscriber data" or the selected PLMN subscription. UE mobility between an SNPN and a PLMN is not supported; n) CIoT 5GS optimizations are not supported; o) void; p) when registering or registered to an SNPN, the UE shall handle the 5GS mobile identity as described in subclause 5.5.1.2.2; q) when registering or registered to an SNPN, the UE shall only consider: 1) a last visited registered TAI visited in the same SNPN as an available last visited registered TAI; or 2) a last visited registered TAI visited using the same entry of the "list of subscriber data" or the same PLMN subscription as an available last visited registered TAI, if the UE supports access to an SNPN using credentials from a credentials holder, equivalent SNPNs or both; NOTE 1: If the last visited registered TAI is assigned by an SNPN other than the current SNPN, the serving AMF can determine the SNPN assigning the last visited registered TAI using the NID provided by the UE. r) emergency service fallback is not supported; s) when registering or registered for onboarding services in SNPN, the UE shall not provide the requested NSSAI to the network; s1) when performing initial registration for onboarding services in SNPN, the UE shall set the 5GS registration type value to "SNPN onboarding registration"; t) when registering or registered for onboarding services in SNPN, the AMF shall not provide the configured NSSAI, the allowed NSSAI or the rejected NSSAI to the UE, shall use the S-NSSAI included in the AMF onboarding configuration data for onboarding services in SNPN and shall not perform NSSAA procedure for S-NSSAI used for onboarding services in SNPN; u) the UE can access an SNPN indicating that onboarding is allowed using default UE credentials for primary authentication in order for the UE to be configured with one or more entries of the "list of subscriber data"; x) eCall over IMS is not supported in SNPN access operation mode and the UE ignores any USIM configuration for eCall only mode; y) when registering or registered for onboarding services in SNPN, the AMF shall store in the 5GMM context of the UE an indication that the UE is registered for onboarding services in SNPN; z) a UE with multiple valid entries of "list of subscriber data", or one or more valid USIMs and one or more valid entries of "list of subscriber data", capable of initiating and maintaining simultaneous separate registration states over 3GPP access with PLMN(s) or SNPN(s), using identities and credentials associated with those entries of "list of subscriber data", or USIMs and entries of "list of subscriber data", and supporting one or more of the N1 NAS signalling connection release, the paging indication for voice services, the reject paging request, the paging restriction and the paging timing collision control may use procedures defined for MUSIM UE, even if the UE does not include multiple valid USIMs; za) when the UE is registering or registered for onboarding services in SNPN, the network slice admission control is not performed; NOTE 2: If the network determines that the UE cannot register to the onboarding SNPN due to lack of resources for the network slice used for onboarding, the AMF can reject the UE with 5GMM cause #22 "congestion". zb) when the UE is registered for onboarding services in SNPN (as specified in subclause 3.1), the UE determines that the number dialled is an emergency number, and emergency services are not supported in the SNPN, the UE shall perform a local de-registration and utilize the procedures specified in 3GPP TS 23.167[ IP Multimedia Subsystem (IMS) emergency sessions ]  [45] and 3GPP TS 24.229[ IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 ]  [13D] to select a domain for the emergency session attempt; and NOTE 4: The UE can select PS domain for emergency session attempt. v) proximity based services (5G ProSe as specified in 3GPP TS 24.554[ Proximity-services (ProSe) in 5G System (5GS) protocol aspects; Stage 3 ]  [19E]) are not supported.