5.4.5.2.3 UE-initiated NAS transport of messages accepted by the network

Upon reception of a UL NAS TRANSPORT message, if the Payload container type IE is set to:

• "N1 SM information", the AMF looks up a PDU session routing context for:
• the UE and the PDU session ID IE in case the Old PDU session ID IE is not included, and:

NOTE 1: If the Old PDU session ID IE is not included in the UL NAS TRANSPORT message and the AMF has received a reallocation requested indication from the SMF, the AMF needs to ignore the reallocation requested indication.

• if the AMF has a PDU session routing context for the PDU session ID and the UE, and the Request type IE is either not included or is included but set to other value than "initial request", "existing PDU session", "initial emergency request", "existing emergency PDU session" or "MA PDU request", the AMF shall send the 5GSM message, and the PDU session ID IE towards the SMF identified by the SMF ID of the PDU session routing context;
• if the AMF has a PDU session routing context for the PDU session ID and the UE, the PDU session routing context indicates that the PDU session is not an emergency PDU session, the Request type IE is included and is set to "existing PDU session" or "MA PDU request", and the S-NSSAI associated with the PDU session identified by the PDU session ID is allowed for the target access type, the AMF shall send the 5GSM message, the PDU session ID, the S-NSSAI, the mapped S-NSSAI (if required as specified in clause 4.6.1), the DNN (if received) and the request type towards the SMF identified by the SMF ID of the PDU session routing context;

iii) if the AMF does not have a PDU session routing context for the PDU session ID and the UE, and the Request type IE is included and is set to "initial request" or "MA PDU request":

A) the AMF shall select an SMF with following handlings in case the UE is not registered for onboarding services in SNPN:

If the S-NSSAI IE is not included, the UE does not have a partially allowed NSSAI, and the allowed NSSAI contains:

• one S-NSSAI, the AMF shall use the S-NSSAI in the allowed NSSAI as the S-NSSAI. Additionally, for a UE for which the AMF has provided a NS-AoS, the AMF shall use the S-NSSAI in the allowed NSSAI if the UE is inside the NS-AoS with respect to the S-NSSAI;
• two or more S-NSSAIs and the user's subscription context obtained from UDM contains only one default S-NSSAI that is included in the allowed NSSAI, the AMF shall use the S-NSSAI in the allowed NSSAI that matches the default S-NSSAI as the S-NSSAI; or
• two or more S-NSSAIs and the user's subscription context obtained from UDM contains two or more default S-NSSAI(s) included in the allowed NSSAI, the AMF shall use an S-NSSAI in the allowed NSSAI selected based on operator policy as the S-NSSAI.

If S-NSSAI IE is not included, the UE has both a partially allowed NSSAI and an allowed NSSAI, the AMF shall select an S-NSSAI from the partially allowed NSSAI or the allowed NSSAI based on operator policy. Additionally:

• for the case when the AMF determines to use the allowed NSSAI for selecting an S-NSSAI and for a UE for which the AMF has provided a NS-AoS, the AMF shall use the S-NSSAI in the allowed NSSAI if the UE is inside the NS-AoS with respect to the S-NSSAI; or
• for the case when the AMF determines to use the partially allowed NSSAI for selecting an S-NSSAI, the AMF shall use the S-NSSAI in the partially allowed NSSAI if the current TAI is in the list of TAs where the S-NSSAI is allowed.

If the UE supports network slice replacement, the S-NSSAI or the mapped S-NSSAI (if available) is an S-NSSAI to be replaced and the alternative S-NSSAI is not provided by the UE, the AMF shall retrieve an alternative S-NSSAI (see clause 5.15.19 of 3GPP TS 23.501 [8]) and initiate the generic UE configuration update procedure as specififed in clause 4.6.3.4 before proceeding with the current procedure.

If the S-NSSAI or the mapped S-NSSAI (if available) is an S-NSSAI to be replaced and the alternative S-NSSAI is provided by the UE, but the AMF determines that the replaced S-NSSAI is available, the AMF shall use the S-NSSAI to be replaced (see clause 5.15.19 of 3GPP TS 23.501 [8]).

If the DNN IE is included, the AMF shall use the UE requested DNN as the DNN determined by the AMF; and

If the DNN IE is not included, and the user's subscription context obtained from UDM:

• contains the default DNN for the S-NSSAI, the AMF shall use the default DNN as the DNN determined by the AMF; and
• does not contain the default DNN for the S-NSSAI, the AMF shall use a locally configured DNN as the DNN determined by the AMF;

A1) the AMF shall select an SMF with following handlings in case the UE is registered for onboarding services in SNPN:

• if the AMF onboarding configuration data does not contain a configured SMF used for onboarding services in SNPN and contains the S-NSSAI used for onboarding services in SNPN, the AMF shall use the S-NSSAI used for onboarding services in SNPN as the S-NSSAI;
• if the AMF onboarding configuration data does not contain a configured SMF used for onboarding services in SNPN and contains the DNN used for onboarding services in SNPN, the AMF shall use the DNN used for onboarding services in SNPN as the DNN;
• if the AMF onboarding configuration data does not contain the S-NSSAI used for onboarding services in SNPN, does not contain the DNN used for onboarding services in SNPN, and contains a configured SMF used for onboarding services in SNPN, the AMF shall select the configured SMF used for onboarding services in SNPN;
• if the AMF onboarding configuration data contains the S-NSSAI used for onboarding services in SNPN, the DNN used for onboarding services in SNPN, or both, and contains a configured SMF used for onboarding services in SNPN, the AMF shall use the S-NSSAI used for onboarding services in SNPN, if any, as the S-NSSAI, and use the DNN used for onboarding services in SNPN, if any, as the DNN or shall select the configured SMF used for onboarding services in SNPN, according to local policy; and
• if the AMF onboarding configuration data contains none of the S-NSSAI used for onboarding services in SNPN, the DNN used for onboarding services in SNPN and a configured SMF used for onboarding services in SNPN, the AMF handling is implementation specific; and

NOTE 2: The AMF can e.g. use a locally configured DNN used for onboarding services in SNPN as the DNN determined by the AMF.

NOTE 3: SMF selection is outside the scope of the present document.

NOTE 4: As part of SMF selection, the PCF can provide the AMF with a DNN selected by the network different from the DNN determined by the AMF.

B) if the SMF selection is successful:

• if the DNN selected by the network is a LADN DNN, the AMF shall determine the UE presence in LADN service area (see clause 6.2.6);
• the AMF shall store a PDU session routing context for the PDU session ID and the UE, shall set the SMF ID in the stored PDU session routing context to the SMF ID corresponding to the DNN in the user's subscription context obtained from the UDM; and
• the AMF shall send the 5GSM message, the PDU session ID, the S-NSSAI, the mapped S-NSSAI (if available), the DNN determined by the AMF, DNN selected by the network (if different from DNN determined by the AMF), the request type, the MA PDU session information, the non-3GPP access path switching indication, UE presence in LADN service area (if DNN received corresponds to an LADN DNN), the onboarding indication (if the UE is registered for onboarding services in SNPN), and the alternative S-NSSAI associated with the S-NSSAI to be replaced (if available) towards the SMF identified by the SMF ID of the PDU session routing context;

NOTE 5: The MA PDU session information is not sent towards the SMF if the DNN received corresponds to an LADN DNN.

• if the AMF does not have a PDU session routing context for the PDU session ID and the UE, the Request type IE is included and is set to "existing PDU session" or "MA PDU request", and the AMF retrieves an SMF ID associated with:

A) the PDU session ID matching the PDU session ID received from the UE, if any; or

B) the DNN matching the DNN received from the UE, otherwise;

such that the SMF ID includes a PLMN identity corresponding to the UE's HPLMN or the current PLMN, then:

A) the AMF shall store a PDU session routing context for the PDU session ID and the UE, shall set the SMF ID in the stored PDU session routing context to the retrieved SMF ID; and

B) the AMF shall send the 5GSM message, the PDU session ID, the S-NSSAI, the mapped S-NSSAI (if available), the DNN (if received) and the request type towards the SMF identified by the SMF ID of the PDU session routing context;

• if the AMF does not have a PDU session routing context for the PDU session ID and the UE, the Request type IE is included and is set to "initial emergency request", and the AMF does not have a PDU session routing context for another PDU session ID of the UE indicating that the PDU session is an emergency PDU session:

A) the AMF shall select an SMF. The AMF shall use the emergency DNN from the AMF emergency configuration data as the DNN, if configured. The AMF shall derive the SMF from the emergency DNN or use the statically configured SMF from the AMF emergency configuration data, if configured; and

B) if the SMF selection is successful:

• the AMF shall store a PDU session routing context for the PDU session ID and the UE, shall set the SMF ID in the stored PDU session routing context to the SMF ID of the selected SMF, and shall store an indication that the PDU session is an emergency PDU session in the stored PDU session routing context; and
• the AMF shall send the 5GSM message, the PDU session ID, the S-NSSAI (if configured in the AMF emergency configuration data), the DNN (if configured in the AMF emergency configuration data), and the request type towards the SMF identified by the SMF ID of the PDU session routing context; and
• if the AMF does not have a PDU session routing context for the PDU session ID and the UE, the Request type IE is included and is set to "initial emergency request", and the AMF has a PDU session routing context indicating that the PDU session is an emergency PDU session for another PDU session ID of the UE:

A) the AMF shall store a PDU session routing context for the PDU session ID and the UE and shall set the SMF ID in the stored PDU session routing context to the SMF ID of the PDU session routing context for the other PDU session ID of the UE; and

B) the AMF shall send the 5GSM message, the PDU session ID, the S-NSSAI (if configured in the AMF emergency configuration data), the DNN (if configured in the AMF emergency configuration data) and the request type towards the SMF identified by the SMF ID of the PDU session routing context; or

vii) if the AMF has a PDU session routing context for the PDU session ID and the UE, the PDU session routing context indicates that the PDU session is an emergency PDU session, and the Request type IE is included and is set to "existing emergency PDU session", the AMF shall send the 5GSM message, the PDU session ID, the S-NSSAI (if configured in the AMF emergency configuration data), the DNN (if configured in the AMF emergency configuration data), and the request type towards the SMF identified by the SMF ID of the PDU session routing context; and

viii) if the AMF does not have a PDU session routing context for the PDU session ID and the UE, the Request type IE is included and is set to "existing emergency PDU session", and the AMF retrieves an SMF ID associated with emergency services such that the SMF ID includes a PLMN identity corresponding to the current PLMN, then:

A) the AMF shall store a PDU session routing context for the PDU session ID and the UE, shall set the SMF ID in the stored PDU session routing context to the retrieved SMF ID; and

B) the AMF shall send the 5GSM message, the PDU session ID, the S-NSSAI (if configured in the AMF emergency configuration data), the DNN (if configured in the AMF emergency configuration data), and the request type towards the SMF identified by the SMF ID of the PDU session routing context; or

• the UE and the Old PDU session ID IE in case the Old PDU session ID IE is included, and:
• the AMF has a PDU session routing context for the old PDU session ID and the UE and does not have a PDU session routing context for the PDU session ID and the UE, the Request type IE is included and is set to "initial request", and the AMF received a reallocation requested indication from the SMF indicating that the SMF is to be reused, the AMF shall store a PDU session routing context for the PDU session ID and the UE, set the SMF ID in the stored PDU session routing context to the SMF ID of the PDU session routing context for the old PDU session ID and the UE. If the DNN is a LADN DNN, the AMF shall determine the UE presence in LADN service area (see clause 6.2.6). The AMF shall send the 5GSM message, the PDU session ID, the old PDU session ID, the S-NSSAI (if received), the mapped S-NSSAI (if available), the DNN, the request type, UE presence in LADN service area (if DNN received corresponds to an LADN DNN), and the alternative S-NSSAI (if received) towards the SMF identified by the SMF ID of the PDU session routing context;
• the AMF has a PDU session routing context for the old PDU session ID and the UE and does not have a PDU session routing context for the PDU session ID and the UE, the Request type IE is included and is set to "initial request", and the AMF received a reallocation requested indication from the SMF indicating that the SMF is to be reallocated:

A) the AMF shall select an SMF with the following handling;

If the S-NSSAI IE is not included and the allowed NSSAI contains:

• one S-NSSAI, the AMF shall use the S-NSSAI in the allowed NSSAI as the S-NSSAI;
• two or more S-NSSAIs and the user's subscription context obtained from UDM contains only one default S-NSSAI that is included in the allowed NSSAI, the AMF shall use the S-NSSAI in the allowed NSSAI that matches the default S-NSSAI; or
• two or more S-NSSAIs and the user's subscription context obtained from UDM contains two or more default S-NSSAI(s) included in the allowed NSSAI, the AMF shall use an S-NSSAI in the allowed NSSAI selected based on operator policy as the S-NSSAI.

If the DNN is a LADN DNN, the AMF shall determine the UE presence in LADN service area (see clause 6.2.6).

B) if the SMF selection is successful:

• the AMF shall store a PDU session routing context for the PDU session ID and the UE and set the SMF ID of the PDU session routing context to the SMF ID of the selected SMF; and
• the AMF shall send the 5GSM message, the PDU session ID, the old PDU session ID, the S-NSSAI, the mapped S-NSSAI (if available), the DNN, the request type, the MA PDU session information, the non-3GPP access path switching indication, UE presence in LADN service area (if DNN received corresponds to an LADN DNN), and the alternative S-NSSAI (if received) towards the SMF identified by the SMF ID of the PDU session routing context for the PDU session ID and the UE;

NOTE 6: The MA PDU session information is not sent towards the SMF if the DNN received corresponds to an LADN DNN.

• "SMS", the AMF shall send the content of the Payload container IE to the SMSF associated with the UE;
• "LTE Positioning Protocol (LPP) message container", the AMF shall send the Payload container type and the content of the Payload container IE to the LMF associated with the routing information included in the Additional information IE of the UL NAS TRANSPORT message;

c1) "SLPP message container", the AMF shall send the Payload container type and the content of the Payload container IE to the LMF associated with the routing information included in the Additional information IE of the UL NAS TRANSPORT message;

• "SOR transparent container", the AMF shall send the content of the Payload container IE to the UDM (see 3GPP TS 29.503 [20AB]);
• "UE policy container", the AMF shall send the content of the Payload container IE to the PCF.
• "UE parameters update transparent container", the AMF shall send the content of the Payload container IE to the UDM.
• "Location services message container":
• if the Additional information IE is not included in the UL NAS TRANSPORT message, the AMF shall provide the Payload container type, the content of the Payload container IE and the content of the Payload container information IE, if included, to the location services application; and
• if the Additional information IE is included in the UL NAS TRANSPORT message, the AMF shall send the Payload container type and the content of the Payload container IE and the content of the Payload container information IE, if included, to an LMF associated with routing information included in the Additional information IE of the UL NAS TRANSPORT message or to a selected LMF if the Payload container information IE is included in the UL NAS TRANSPORT message and the PRU bit of the Payload container information IE indicates "Payload container related to PRU".
• "CIoT user data container", the AMF shall look up a PDU session routing context for the UE and the PDU session ID, and
• send the content of the Payload container IE towards the SMF identified by the SMF ID of the PDU session routing context; and
• initiate the release of the N1 NAS signalling connection:
• if the Release assistance indication IE is included in the UL NAS TRANSPORT message and the DDX field of the Release assistance indication IE indicates "No further uplink and no further downlink data transmission subsequent to the uplink data transmission is expected" and if there is no downlink signalling or downlink data for the UE; or
• upon subsequent delivery of the next received downlink data transmission to the UE if the Release assistance indication IE is included in the UL NAS TRANSPORT message and the DDX field of the Release assistance indication IE indicates "Only a single downlink data transmission and no further uplink data transmission subsequent to the uplink data transmission is expected" and if there is no additional downlink signalling or downlink data for the UE.
• "Service-level-AA container" and the Service-level-AA container is included in the Payload container IE of the UL NAS TRANSPORT message, and the Service-level device ID included in the Service-level-AA container is set to a CAA-level UAV ID, the AMF shall send the content of the Payload container IE to the UAS-NF corresponding to the CAA-level UAV ID. If the Service-level device ID is not included in the Service-level-AA container and a CAA-level UAV ID is included in the 5GMM context of the UE, then the AMF shall send the content of the Payload container IE to the UAS-NF corresponding to the CAA-level UAV ID included in the 5GMM context of the UE.
• "UPP-CMI container":
• if the Additional information IE is not included in the UL NAS TRANSPORT message, the AMF shall provide the Payload container type and the content of the Payload container IE to the location services application; or
• if the Additional information IE is included in the UL NAS TRANSPORT message, the AMF shall send the Payload container type and the content of the Payload container IE to an LMF associated with routing information included in the Additional information IE of the UL NAS TRANSPORT message.

NOTE 7: LMF selection for user plane positioning is outside the scope of the present document.

• "Multiple payloads", the AMF shall first decode the content of the Payload container IE (see clause 9.11.3.39) to obtain the number of payload container entries and for each payload container entry, the AMF shall:
• decode the payload container type field;
• decode the optional IE fields and the payload container contents field in the payload container entry; and

iii) handle the content of each payload container entry the same as the content of the Payload container IE and the associated optional IEs as specified in bullets a) to j) above according to the payload container type field.