Section: 5.4.5.3.2 Network-initiated NAS transport procedure initiation
Content: In 5GMM-CONNECTED mode, the AMF initiates the NAS transport procedure by sending the DL NAS TRANSPORT message, as shown in figure 5.4.5.3.2.1. In case a) in subclause 5.4.5.3.1, i.e. upon reception from an SMF of a 5GSM message without an N1 SM delivery skip allowed indication for a UE or a 5GSM message with an N1 SM delivery skip allowed indication for a UE in the 5GMM-CONNECTED mode, the AMF shall: a) include the PDU session information (PDU session ID) in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; and c) set the Payload container IE to the 5GSM message. In case b) in subclause 5.4.5.3.1, i.e. upon reception from an SMSF of an SMS payload, the AMF shall: a) set the Payload container type IE to "SMS"; b) set the Payload container IE to the SMS payload; and c) select the access type to deliver the DL NAS TRANSPORT message as follows in case the access type selection is required: 1) if the UE to receive the DL NAS TRANSPORT message is registered to the network via both 3GPP access and non-3GPP access, the 5GMM context of the UE indicates that SMS over NAS is allowed, the UE is in MICO mode, and the UE is in 5GMM-IDLE mode for 3GPP access and in 5GMM-CONNECTED mode for non-3GPP access, then the AMF selects non-3GPP access. Otherwise, the AMF selects either 3GPP access or non-3GPP access. If the delivery of the DL NAS TRANSPORT message over 3GPP access has failed, the AMF may re-send the DL NAS TRANSPORT message over the non-3GPP access. If the delivery of the DL NAS TRANSPORT message over non-3GPP access has failed, the AMF may re-send the DL NAS TRANSPORT message over the 3GPP access; and 2) otherwise, the AMF selects 3GPP access. NOTE 1: The AMF selects an access type between 3GPP access and non-3GPP access based on operator policy. In case c) in subclause 5.4.5.3.1 i.e. upon reception from an LMF of an LPP message payload, the AMF shall: a) set the Payload container type IE to "LTE Positioning Protocol (LPP) message container"; b) set the Payload container IE to the LPP message payload received from the LMF; c) set the Additional information IE to an LCS correlation identifier received from the LMF from which the LPP message was received. NOTE 2: The LCS Correlation Identifier is assigned originally by the AMF except for LPP message transfer associated with event reporting for periodic or triggered location as described in subclause 6.3.1 of 3GPP TS 23.273[ 5G System (5GS) Location Services (LCS); Stage 2 ]  [6B], where the LMF assigns the correlation identifier. AMF and LMF assigned correlation identifiers can be distinguished by an implementation specific convention (e.g. use of a different number of octets) to enable an AMF to distinguish one from the other when received in the Additional Information IE in an UL NAS Transport message. In case c1) in subclause 5.4.5.3.1 i.e. upon reception from an LMF of an SLPP message payload, the AMF shall: a) set the Payload container type IE to "SLPP message container"; b) set the Payload container IE to the SLPP message payload received from the LMF; and c) set the Additional information IE to an LCS correlation identifier received from the LMF from which the SLPP message was received. In case d) in subclause 5.4.5.3.1 i.e. upon reception of a steering of roaming information (see 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [5]) from the UDM to be forwarded to the UE, the AMF shall: a) set the Payload container type IE to "SOR transparent container"; and b) set the Payload container IE to the steering of roaming information received from the UDM (see 3GPP TS 29.503[ 5G System; Unified Data Management Services; Stage 3 ]  [20AB]). In case e) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded due to routing failure, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; d) set the 5GMM cause IE to the 5GMM cause #90 "payload was not forwarded" or 5GMM cause #91 "DNN not supported or not subscribed in the slice". The AMF sets the 5GMM cause IE to the 5GMM cause #91 "DNN not supported or not subscribed in the slice", if the 5GSM message could not be forwarded since SMF selection fails because: 1) the DNN is not supported in the slice identified by the S-NSSAI used by the AMF; or 2) neither the DNN provided by the UE nor the wildcard DNN are in the subscribed DNN list of the UE for the S-NSSAI used by the AMF. Otherwise, the AMF sets the 5GMM cause IE to the 5GMM cause #90 "payload was not forwarded"; and e) optionally include the Back-off timer value IE if the 5GMM cause IE is set to 5GMM cause #91 "DNN not supported or not subscribed in the slice" due to the DNN is not supported in the slice. In case f) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded due to congestion control, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; d) set the 5GMM cause IE to the 5GMM cause #22 "Congestion", the 5GMM cause #67 "insufficient resources for specific slice and DNN" or the 5GMM cause #69 "insufficient resources for specific slice"; and e) include the Back-off timer value IE. In case g) in subclause 5.4.5.3.1, i.e. upon reception of a UE policy container from the PCF to be forwarded to the UE, the AMF shall: a) set the Payload container type IE to "UE policy container"; and b) set the Payload container IE to the UE policy container received from the PCF. In case h) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded, because the PLMN's maximum number of PDU sessions has been reached, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; and d) set the 5GMM cause IE to the 5GMM cause #65 "maximum number of PDU sessions reached". In case h1) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded, because the maximum number of PDU sessions with active user-plane resources has been reached, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; and d) set the 5GMM cause IE to the 5GMM cause #92 "insufficient user-plane resources for the PDU session". In case h2) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded because the UE requested to establish a PDU session associated with an S-NSSAI or to modify a PDU session associated with an S-NSSAI for which: a) the AMF is performing network slice-specific authentication and authorization and determined to reject the request based on local policy; or b) the network slice-specific authentication and authorization has failed or the authorization has been revoked; the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; and d) set the 5GMM cause IE to the 5GMM cause #90 "payload was not forwarded". In case h3) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded because the UE requested to establish an MA PDU session for LADN DNN, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; and d) set the 5GMM cause IE to the 5GMM cause #90 "payload was not forwarded". In case h4) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded, because the maximum number of UEs for a network slice has been reached, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; d) set the 5GMM cause IE to the 5GMM cause #69 "insufficient resources for specific slice"; and e) include the Back-off timer value IE. For case h5) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded because the UE is marked in the UE's 5GMM context that it is not allowed to request UAS services, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; and d) set the 5GMM cause IE to the 5GMM cause #79 "UAS services not allowed". For case h6) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded because because the UE not supporting S-NSSAI location validity information requested forwarding of an 5GSM message with Request type IE is set to "initial request" when not in the NS-AoS of the related S-NSSAI, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; d) set the 5GMM cause IE to the 5GMM cause #69 "insufficient resources for specific slice"; and e) include the Back-off timer value IE. In case i) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded due to service area restrictions, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; and d) set the 5GMM cause IE to the 5GMM cause #28 "Restricted service area". In case i1) in subclause 5.4.5.3.1, i.e. upon sending a single uplink 5GSM message which was not forwarded because the UE is registered to a PLMN via a satellite NG-RAN cell that is not allowed to operate at the present UE location, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "N1 SM information"; c) set the Payload container IE to the 5GSM message which was not forwarded; and d) set the 5GMM cause IE to the 5GMM cause #78 "PLMN not allowed to operate at the present UE location". In case j) in subclause 5.4.5.3.1 i.e. upon reception of UE parameters update data (see 3GPP TS 23.502[ Procedures for the 5G System (5GS) ]  [9]) from the UDM to be forwarded to the UE, the AMF shall: a) set the Payload container type IE to "UE parameters update transparent container"; and b) set the contents of the Payload container IE to the UE parameters update data (see 3GPP TS 23.502[ Procedures for the 5G System (5GS) ]  [9]) received from the UDM. For case k) in subclause 5.4.5.3.1 upon reception from a location services application of a Location services message payload, the AMF shall: a) set the Payload container type IE to "Location services message container"; and b) set the Payload container IE to the Location services message payload. For case k) in subclause 5.4.5.3.1 upon reception from an LMF of a Location services message payload, the AMF shall: a) set the Payload container type IE to "Location services message container"; b) set the Payload container IE to the Location services message payload; and c) set the Additional information IE to routing information associated with the LMF from which the Location services message payload was received. NOTE 3: Case k) in subclause 5.4.5.3.1 supports transport of a Location services message container between a UE and an AMF and between a UE and an LMF. For transport between a UE and an LMF, the Additional information IE is included and provides routing information for the LMF. For transport between a UE and an AMF, the Additional information IE is not included. In case l) in subclause 5.4.5.3.1, i.e. upon reception from an SMF of a user data container payload, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "CIoT user data container"; and c) set the Payload container IE to the user data container. For case l1) in subclause 5.4.5.3.1, i.e. upon sending a single uplink CIoT user data container or control plane user data which was not forwarded due to routing failure, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to "CIoT user data container"; c) set the Payload container IE to the CIoT user data container or control plane user data which was not forwarded; and d) set the 5GMM cause IE to the 5GMM cause #90 "payload was not forwarded". NOTE 4: For case l1) in subclause 5.4.5.3.1, this is also applied for a single uplink CIoT user data container or control plane user data in the CONTROL PLANE SERVICE REQUEST message which was not forwarded due to routing failure. For case l2) in subclause 5.4.5.3.1, i.e. upon sending a single uplink CIoT user data container which was not forwarded due to congestion control, the AMF shall: a) include the PDU session ID in the PDU session ID IE; b) set the Payload container type IE to " CIoT user data container"; c) set the Payload container IE to the CIoT user data container which was not forwarded; d) set the 5GMM cause IE to the 5GMM cause #22 "Congestion", the 5GMM cause #67 "insufficient resources for specific slice and DNN" or the 5GMM cause #69 "insufficient resources for specific slice", and include the Back-off timer value IE. In case m) in subclause 5.4.5.3.1, during UUAA-MM procedure, if the AMF receives the UUAA payload from the UAS-NF, the AMF shall: a) include the service-level-AA payload with the value set to the payload; and b) if a payload type associated with the payload is received, include the service-level-AA payload type with the value set to the payload type In case m1) in subclause 5.4.5.3.1, i.e. if the AMF needs to send an event notification indicator for upper layers to the UE which set the "EventNotification" bit of the 5GMM capability IE in the last REGISTRATION REQUEST message to "Event notification supported", the AMF shall: a) set the Payload container type IE to "Event notification"; and b) set the Payload container IE to the event notification indicator. In case m2) in subclause 5.4.5.3.1, i.e. upon reception from an LMF of a UPP-CMI container, the AMF shall: a) set the Payload container type IE to "UPP-CMI container"; b) set the Payload container IE to the UPP-CMI container received from the LMF; and c) set the Additional information IE to routing information associated with the LMF from which the Location services message payload was received. For case m3) in subclause 5.4.5.3.1, i.e. upon sending a single UPP-CMI container which was not forwarded due to user plane positioning not authorized, the AMF shall: a) set the Payload container type IE to "UPP-CMI container"; b) set the Payload container IE to the UPP-CMI container which was not forwarded; and c) set the 5GMM cause IE to the 5GMM cause #94 "User plane positioning not authorized". In case n) in subclause 5.4.5.3.1, the AMF shall: a) set the Payload container type IE to "Multiple payloads"; b) set each payload container entry of the Payload container IE (see subclause 9.11.3.39) as follows: i) set the payload container type field of the payload container entry to a payload container type value set in the Payload container type IE as specified for cases a) to m3) above; ii) set the payload container entry contents field of the payload container entry to the payload container contents set in the Payload container IE as specified for cases a) to m3) above; iii) set the optional IE fields, if any, to the optional associated information as specified for cases a) to m3) above. Figure 5.4.5.3.2.1: Network-initiated NAS transport procedure