Content for  TS 24.501  Word version:  19.0.0

If the mobility and periodic registration update request cannot be accepted by the network, the AMF shall send a REGISTRATION REJECT message to the UE including an appropriate 5GMM cause value. If the mobility and periodic registration update request is rejected due to general NAS level mobility management congestion control, the network shall set the 5GMM cause value to #22 "congestion" and assign a value for back-off timer T3346. If the mobility and periodic registration update request is rejected due to general NAS level mobility management congestion control for the SNPN selected for localized services in SNPN (see TS 23.122), the network may set an appropriate cause value other than 5GMM cause value to #22 "congestion" and does not assign a value for back-off timer T3346. In NB-N1 mode, if the mobility and periodic registration update request is rejected due to operator determined barring (see TS 29.503), the network shall set the 5GMM cause value to #22 "congestion" and assign a value for back-off timer T3346. When the UE performs inter-system change from S1 mode to N1 mode, if the AMF is informed that verification of the integrity protection of the TRACKING AREA UPDATE REQUEST message included by the UE in the EPS NAS message container IE of the REGISTRATION REQUEST message has failed in the MME, then:

1. If the AMF can retrieve the current 5G NAS security context as indicated by the ngKSI and 5G-GUTI sent by the UE, the AMF shall proceed as specified in subclause 5.5.1.3.4;
2. if the AMF cannot retrieve the current 5G NAS security context as indicated by the ngKSI and 5G-GUTI sent by the UE, or the ngKSI or 5G-GUTI was not sent by the UE, the AMF may initiate the identification procedure by sending the IDENTITY REQUEST message with the "Type of identity" of the 5GS identity type IE set to "SUCI" before taking actions as specified in subclause 4.4.4.3; or
3. If the AMF needs to reject the mobility and periodic registration update procedure, the AMF shall send REGISTRATION REJECT message including 5GMM cause #9 "UE identity cannot be derived by the network".

If the REGISTRATION REJECT message with 5GMM cause #76 or #78 was received without integrity protection, then the UE shall discard the message. If the REGISTRATION REJECT message with 5GMM cause #62 was received without integrity protected, the behaviour of the UE is specified in subclause 5.3.20.2. Based on operator policy, if the mobility and periodic registration update request is rejected due to core network redirection for CIoT optimizations, the network shall set the 5GMM cause value to #31 "Redirection to EPC required". If the mobility and periodic registration update request is rejected because:

1. all the S-NSSAI(s) included in the requested NSSAI (i.e. Requested NSSAI IE or Requested mapped NSSAI IE) are rejected;
2. the UE set the NSSAA bit in the 5GMM capability IE to:
   1. "Network slice-specific authentication and authorization supported" and;
      1. void;
      2. all default S-NSSAIs are not allowed; or
      3. network slice-specific authentication and authorization has failed or been revoked for all default S-NSSAIs and based on network local policy, the network decides not to initiate the network slice-specific re-authentication and re-authorization procedures for any default S-NSSAI requested by the UE; or
   2. "Network slice-specific authentication and authorization not supported" and all subscribed default S-NSSAIs marked as default are either not allowed or are subject to network slice-specific authentication and authorization; and
      1. void; or
      2. void; and
3. no emergency PDU session has been established for the UE;

the network shall set the 5GMM cause value of the REGISTRATION REJECT message to #62 "No network slices available" and shall include, in the rejected NSSAI of the REGISTRATION REJECT message, all the S-NSSAI(s) which were included in the requested NSSAI. If the UE has set the ER-NSSAI bit to "Extended rejected NSSAI supported" in the 5GMM capability IE of the REGISTRATION REQUEST message, the rejected S-NSSAI(s) shall be included in the Extended rejected NSSAI IE of the REGISTRATION REJECT message. Otherwise, the rejected S-NSSAI(s) shall be included in the Rejected NSSAI IE of the REGISTRATION REJECT message. In roaming scenarios, if the Extended rejected NSSAI IE is included in the REGISTRATION REJECT message, the AMF shall provide mapped S-NSSAI(s) for the rejected NSSAI. If the UE supports extended rejected NSSAI and the AMF determines that maximum number of UEs reached for one or more S-NSSAI(s) in the requested NSSAI as specified in subclause 4.6.2.5, the AMF shall include the rejected NSSAI containing one or more S-NSSAIs with the rejection cause "S-NSSAI not available due to maximum number of UEs reached" in the Extended rejected NSSAI IE in the REGISTRATION REJECT message. In addition, the AMF may include a back-off timer value for each S-NSSAI with the rejection cause "S-NSSAI not available due to maximum number of UEs reached" in the Extended rejected NSSAI IE of the REGISTRATION REJECT message. If the mobility and periodic registration update request from a UE supporting CAG is rejected due to CAG restrictions, the network shall set the 5GMM cause value to #76 "Not authorized for this CAG or authorized for CAG cells only" and should include the "CAG information list" in the CAG information list IE or the Extended CAG information list IE in the REGISTRATION REJECT message. If the UE does not support extended CAG information list, the CAG information list shall not be included in the Extended CAG information list IE. If the mobility and periodic registration update request from a UE not supporting CAG is rejected due to CAG restrictions, the network shall operate as described in bullet i) of subclause 5.5.1.3.8. If the UE's mobility and periodic registration update request is via a satellite NG-RAN cell and the network determines that the UE is in a location where the network is not allowed to operate, see TS 23.502, the network shall set the 5GMM cause value in the REGISTRATION REJECT message to #78 "PLMN not allowed at the present UE location". If the AMF receives the mobility and periodic registration update request including the service-level device ID set to the CAA-level UAV ID in the Service-level-AA container IE and the AMF determines that the UE is not allowed to use UAS services via 5GS based on the user's subscription data and the operator policy, the AMF shall return a REGISTRATION REJECT message with 5GMM cause #79 "UAS services not allowed". If the mobility and periodic registration update request from a UE supporting MINT is rejected due to a disaster condition no longer being applicable in the current location of the UE, the network shall set the 5GMM cause value to #11 "PLMN not allowed" or #13 "Roaming not allowed in this tracking area" and may include a disaster return wait range in the Disaster return wait range IE in the REGISTRATION REJECT message. If the UE initiates the registration procedure for disaster roaming and the AMF determines that it does not support providing disaster roaming services for the determined PLMN with disaster condition to the UE, then the AMF shall send a REGISTRATION REJECT message with 5GMM cause #80 "Disaster roaming for the determined PLMN with disaster condition not allowed". If the AMF receives the mobility and periodic registration update request over non-3GPP access and detects that the N3IWF used by the UE is not compatible with the allowed NSSAI and the UE has indicated its support for slice-based N3IWF selection in the REGISTRATION REQUEST message, the AMF may send a REGISTRATION REJECT message with 5GMM cause #81 "Selected N3IWF is not compatible with the allowed NSSAI" and may provide information for a suitable N3IWF in the REGISTRATION REJECT message indicating the suitable N3IWF that is compatible with the requested NSSAI. If the AMF receives the mobility and periodic registration update request over non-3GPP access and detects that the TNGF used by the UE is not compatible with the allowed NSSAI and the UE has indicated its support for slice-based TNGF selection in the REGISTRATION REQUEST message, the AMF may send a REGISTRATION REJECT message with 5GMM cause #82 "Selected TNGF is not compatible with the allowed NSSAI" and may provide information for a suitable TNAN in the TNAN information IE in the REGISTRATION REJECT message indicating the suitable TNGF that is compatible with the requested NSSAI. If the AMF received multiple TAIs from the satellite NG-RAN as described in TS 23.501, and determines that, by UE subscription and operator's preferences, all of the received TAIs are forbidden for roaming or for regional provision of service, the AMF shall include the TAI(s) in:

1. the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE; or
2. the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for regional provision of service" IE; or
3. both;

in the REGISTRATION REJECT message. Regardless of the 5GMM cause value received in the REGISTRATION REJECT message via satellite NG-RAN,

• if the UE receives the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE in the REGISTRATION REJECT message and if the TAI(s) included in the IE is not part of the list of "5GS forbidden tracking areas for roaming", the UE shall store the TAI(s) belonging to the serving PLMN or equivalent PLMN(s) and ignore the TAI(s) which do not belong to the serving PLMN or equivalent PLMN(s) included in the IE, if not already stored, into the list of "5GS forbidden tracking areas for roaming"; and
• if the UE receives the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for regional provision of service" IE in the REGISTRATION REJECT message and if the TAI(s) included in the IE is not part of the list of "5GS forbidden tracking areas for regional provision of service", the UE shall store the TAI(s) belonging to the serving PLMN or equivalent PLMN(s) and ignore the TAI(s) which do not belong to the serving PLMN or equivalent PLMN(s) included in the IE, if not already stored, into the list of "5GS forbidden tracking areas for regional provision of service".

In a shared network, the UE shall construct the TAI of the cell from one of the PLMN identities as specified in TS 23.122 and the TAC received on the broadcast system information. Whenever a REGISTRATION REJECT message is received by the UE:

• with the 5GMM cause #11 "PLMN not allowed" or #36 "IAB-node operation not authorized", the chosen PLMN identity shall be stored in the "forbidden PLMN list" and if the UE is configured to use timer T3245 (see TS 24.368 or TS 31.102) then the UE shall start timer T3245 and proceed as described in subclause 5.3.19A;
• with the 5GMM cause #12 "tracking area not allowed", #13 "roaming not allowed in this tracking area", #15 "no suitable cells in tracking Area", or #62 "No network slices available", the constructed TAI shall be stored in the suitable list; or
• as a response to registration procedure for mobility registration update initiated in 5GMM-CONNECTED mode, the UE need not update forbidden lists with the selected PLMN identity or the constructed TAI, respectively.

In a shared network, the UE shall construct the TAI of the cell from one of the SNPN identities as specified in TS 23.122 constructing the TAI from the PLMN identity part of the SNPN identity and the TAC received on the broadcast system information. Whenever a REGISTRATION REJECT message is received by the UE:

• with the 5GMM cause #74 "Temporarily not authorized for this SNPN", the chosen SNPN identity shall be stored in the "temporarily forbidden SNPNs" list, "temporarily forbidden SNPNs for access for localized services in SNPN" list if the SNPN is an SNPN selected for localized services in SNPN (see TS 23.122) or "temporarily forbidden SNPNs for onboarding services in SNPN" list if the UE is registered for onboarding services in SNPN and if the UE is configured to use timer T3245 (see TS 24.368 or TS 31.102) then the UE shall start timer T3245 and proceed as described in subclause 5.3.19A;
• with the 5GMM cause #75 "Permanently not authorized for this SNPN", the chosen SNPN identity shall be stored in the "permanently forbidden SNPNs", "permanently forbidden SNPNs for access for localized services in SNPN" list if the SNPN is an SNPN selected for localized services in SNPN (see TS 23.122) for the selected entry of the "list of subscriber data" or the selected PLMN subscription or "permanently forbidden SNPNs for onboarding services in SNPN" if the UE is registered for onboarding services in SNPN and if the UE is configured to use timer T3245 (see TS 24.368 or TS 31.102) then the UE shall start timer T3245 and proceed as described in subclause 5.3.19A;
• with the 5GMM cause #12 "tracking area not allowed", #13 "roaming not allowed in this tracking area", #15 "no suitable cells in tracking Area", or #62 "No network slices available", the constructed TAI shall be stored in the suitable list; or
• as a response to registration procedure for mobility registration update initiated in 5GMM-CONNECTED mode, the UE need not update forbidden lists with the selected SNPN identity or the constructed TAI, respectively.

Furthermore, the UE shall take the following actions depending on the 5GMM cause value received in the REGISTRATION REJECT message. Other values are considered as abnormal cases. The behaviour of the UE in those cases is specified in subclause 5.5.1.3.7.

If the mobility and periodic registration update request for initiating an emergency PDU session cannot be accepted by the network, the UE shall perform the procedures as described in subclause 5.5.1.3.5. If the mobility and periodic registration update request for initiating an emergency PDU session fails due to receiving the AUTHENTICATION REJECT message, the UE shall perform the procedures as described in subclauses 5.4.1.2.2.11, 5.4.1.2.3.1, 5.4.1.2.3A.1 or 5.4.1.3.5. Then if the UE is in the same selected PLMN where the last mobility and periodic registration update request was attempted, the UE shall:

1. inform the upper layers of the failure of the procedure; or
2. perform de-registration locally, if not de-registered already, and attempt initial registration for emergency services.

If the mobility and periodic registration update request for initiating an emergency PDU session fails due to abnormal case b) in subclause 5.5.1.3.7, the UE shall perform the actions as described in subclause 5.5.1.3.7 and inform the upper layers of the failure to access the network. If the mobility and periodic registration update request for initiating an emergency PDU session fails due to abnormal cases c), d), e) or g) in subclause 5.5.1.3.7, the UE shall perform the procedures as described in subclause 5.5.1.3.7. Then if the UE is in the same selected PLMN where the last mobility and periodic registration update request was attempted, the UE shall:

1. inform the upper layers of the failure of the procedure; or
2. perform de-registration locally, if not de-registered already, and attempt initial registration for emergency services.

If the mobility and periodic registration update request triggered upon receiving a request from the upper layers to perform an emergency services fallback:

• fails due to an abnormal case described in subclause 5.5.1.3.7, the UE shall perform the procedures as described in subclause 5.5.1.3.7;
• cannot be accepted by the network as described in subclause 5.5.1.3.5, the UE shall perform the procedures as described in subclause 5.5.1.3.5; or
• fails due to receiving the AUTHENTICATION REJECT message, the UE shall perform the procedures as described in subclauses 5.4.1.2.2.11, 5.4.1.2.3.1, 5.4.1.2.3A.1 or 5.4.1.3.5.

If the mobility and periodic registration update request triggered upon receiving a request from the upper layers to perform an emergency services fallback fails due to abnormal case b) in subclause 5.5.1.3.7, the UE shall inform the upper layers of the failure to access the network. If the mobility and periodic registration update request triggered upon receiving a request from the upper layers to perform an emergency services fallback fails due to abnormal cases c), d), e) or g), cannot be accepted or fails due to receiving the AUTHENTICATION REJECT message and the UE does not attempt to select an E-UTRA cell connected to EPC or 5GCN as described in subclause 5.5.1.3.5 and the UE is camped on NR or E-UTRA cell connected to 5GCN in the same PLMN where the last mobility and periodic registration update request was attempted, the UE shall inform the upper layers of the failure of the procedure.

The following abnormal cases can be identified: For the cases c, d and e the UE shall proceed as follows:

The following abnormal cases can be identified:

1. Lower layer failure
   If a lower layer failure occurs before the message REGISTRATION COMPLETE has been received from the UE and timer T3550 is running, the AMF shall abort the procedure, enter 5GMM-IDLE mode.
   If a new 5G-GUTI was assigned to the UE in the REGISTRATION ACCEPT message, the AMF shall consider both, the old and new 5G-GUTIs as valid until the old 5G-GUTI can be considered as invalid by the AMF. If a new TAI list was provided in the REGISTRATION ACCEPT message, both the old and new TAI lists shall also be considered valid until the old TAI list can be considered invalid by the AMF. If the old 5G-GUTI was allocated by an AMF other than the current AMF, the current AMF does not need to retain the old 5G-GUTI.
   Additionally, if the REGISTRATION ACCEPT message includes:
   1. Negotiated PEIPS assistance information IE:
      1. containing a new Paging subgroup ID and the UE is previously assigned a different Paging subgroup ID then, the AMF shall consider both, the old and new Paging subgroup IDs as valid until the old Paging subgroup ID can be considered as invalid by the AMF; or
      2. containing no Paging subgroup ID or no Negotiated PEIPS assistance information IE, then the AMF shall delete any old Paging subgroup ID stored in the 5GMM context of the UE.
   2. Negotiated WUS assistance information IE:
      1. containing a new UE paging probability information value and the UE is previously assigned a different UE paging probability information value then, the AMF shall consider both, the old and new UE paging probability information values as valid until the old UE paging probability information value can be considered as invalid by the AMF; or
      2. containing no UE paging probability information value or no Negotiated WUS assistance information IE, then the AMF shall delete any old UE paging probability information value stored in the 5GMM context of the UE.
   During this period:
   1. if the new 5G-GUTI is used by the UE in a subsequent message, then:
      1. the AMF shall consider the old 5G-GUTI as invalid and, additionally, the old TAI list as invalid if a new TAI list was provided with the new 5G-GUTI in the REGISTRATION ACCEPT message;
      2. if the AMF assigns a new Paging subgroup ID to the UE in the REGISTRATION ACCEPT message, then, the AMF shall consider the new Paging subgroup ID as valid and the old Paging subgroup ID, if any, as invalid; and
      3. if the AMF assigns a new UE paging probability information value in the Negotiated WUS assistance information IE to the UE in the REGISTRATION ACCEPT message, then, the AMF shall consider the new UE paging probability information value as valid and the old UE paging probability information value, if any, as invalid.
   2. if the old 5G-GUTI is used by the UE in a subsequent message, the AMF may use the identification procedure followed by a generic UE configuration update procedure. If the AMF in the REGISTRATION ACCEPT message:
      1. assigns a new Paging subgroup ID to the UE, then, the AMF shall include the PEIPS assistance information; or
      2. does not assign a Paging subgroup ID to the UE then, the AMF shall not include the PEIPS assistance information;
      and initiate the generic UE configuration update procedure; and
   3. if the UE needs to be paged:
      1. if in the REGISTRATION ACCEPT message a new Paging subgroup ID in the Negotiated PEIPS assistance information IE is assigned to the UE:
         • that previously has no Paging subgroup ID assigned then, the AMF shall use the new Paging subgroup ID for paging the UE;
         • that is same as the old Paging subgroup ID then, the AMF shall use the same Paging subgroup ID for paging the UE; or
         • that is different than the old Paging subgroup ID then, the AMF may first use the old Paging subgroup ID followed by the new Paging subgroup ID for paging the UE.
      2. if in the REGISTRATION ACCEPT message a new UE paging probability information value in the Negotiated WUS assistance information IE is assigned to the UE:
         • that previously has no UE paging probability information value assigned then, the AMF shall use the new UE paging probability information value for paging the UE;
         • that is same as the old UE paging probability information value then, the AMF shall use the same UE paging probability information value for paging the UE; or
         • that is different than the old UE paging probability information value then, the AMF may first use the old UE paging probability information value followed by the new UE paging probability information value for paging the UE.
      3. the AMF selects the 5G-GUTI and TAI list as follows:
         • the AMF may first use the old 5G-S-TMSI from the old 5G-GUTI for paging within the area defined by the old TAI list for an implementation dependent number of paging attempts using the selected Paging subgroup ID or the selected UE paging probability information value in the WUS assistance information IE. If a new TAI list was provided in the REGISTRATION ACCEPT message, the new TAI list should also be used for paging. Upon response from the UE, the AMF may initiate the generic UE configuration update procedure. If the response is received from a tracking area within the old and new TAI list, the network shall initiate the generic UE configuration update procedure. If in the REGISTRATION ACCEPT message a new Paging subgroup ID was assigned to the UE that is different than the old Paging subgroup ID then the network shall initiate the generic UE configuration update procedure; and
         • if no response is received to the paging attempts using the old 5G-S-TMSI from the old 5G-GUTI and the old Paging subgroup ID or the old UE paging probability information value in the WUS assistance information IE, the AMF may use the new 5G-S-TMSI from the new 5G-GUTI and the new Paging subgroup ID or the new UE paging probability information value in the WUS assistance information IE, if any, for paging, for an implementation dependent number of paging attempts. In this case, if a new TAI list was provided with the new 5G-GUTI in the REGISTRATION ACCEPT message, the new TAI list shall be used instead of the old TAI list.
2. Protocol error.
   If the REGISTRATION REQUEST message has been received with a protocol error, the AMF shall return a REGISTRATION REJECT message with one of the following 5GMM cause values:
   #96

   invalid mandatory information;

   #99

   information element non-existent or not implemented;

   #100

   conditional IE error; or

   #111

   protocol error, unspecified.
3. T3550 time out.
   On the first expiry of the timer, the AMF shall retransmit the REGISTRATION ACCEPT message and shall reset and restart timer T3550. The retransmission is performed four times, i.e. on the fifth expiry of timer T3550, the registration procedure for mobility and periodic registration update procedure is aborted.
   During this period the AMF acts as described for case a) above.
4. REGISTRATION REQUEST with 5GS registration type IE set to "mobility registration updating" or "periodic registration updating" received after the REGISTRATION ACCEPT message has been sent and before the REGISTRATION COMPLETE message is received, if the REGISTRATION COMPLETE message is expected.
   1. If one or more of the information elements in the REGISTRATION REQUEST message differ from the ones received within the previous REGISTRATION REQUEST message, the previously initiated registration procedure for mobility and periodic registration update shall be aborted if the REGISTRATION COMPLETE message has not been received and the new registration procedure for mobility and periodic registration update shall be progressed; or
   2. if the information elements do not differ, then the REGISTRATION ACCEPT message shall be resent and timer T3550 shall be restarted. In that case, the retransmission counter related to timer T3550 is not incremented.
5. More than one REGISTRATION REQUEST message with 5GS registration type IE set to "mobility registration updating" or "periodic registration updating" received and neither REGISTRATION ACCEPT message nor REGISTRATION REJECT message has been sent.
   1. If one or more of the information elements in the REGISTRATION REQUEST message differs from the ones received within the previous REGISTRATION REQUEST message, the previously initiated registration procedure for mobility and periodic registration update shall be aborted and the new registration procedure for mobility and periodic registration update shall be progressed; or
   2. if the information elements do not differ, then the network shall continue with the previous registration procedure for mobility and periodic registration update and shall not treat any further this REGISTRATION REQUEST message.
6. Lower layers indication of non-delivered NAS PDU due to handover.
   If the REGISTRATION ACCEPT message or REGISTRATION REJECT message could not be delivered due to an intra AMF handover and the target TA is included in the TAI list, then upon successful completion of the intra AMF handover the AMF shall retransmit the REGISTRATION ACCEPT message or REGISTRATION REJECT message. If a failure of the handover procedure is reported by the lower layer and the N1 NAS signalling connection exists, the AMF shall retransmit the REGISTRATION ACCEPT message or REGISTRATION REJECT message.
7. DEREGISTRATION REQUEST message received before REGISTRATION COMPLETE message is received, if the REGISTRATION COMPLETE message is expected.
   If the De-registration type IE is set to "switch off":
   The AMF shall abort the signalling for the registration procedure for mobility and periodic registration update towards the UE and shall progress the de-registration procedure as described in subclause 5.5.2.2.
   If the De-registration type IE is set to other type than "switch off":
   The AMF shall proceed with registration procedure for mobility and periodic registration update and shall progress the de-registration procedure after successful completion of the registration procedure for mobility and periodic registration update.
8. If the REGISTRATION REQUEST message with 5GS registration type IE indicating "periodic registration updating" is received by the new AMF which does not have the 5GMM context data related to the subscription, the new AMF may send the REGISTRATION REJECT message with 5GMM cause #10 "implicitly de-registered".
9. Based on operator policy, if the mobility and periodic registration update request from a UE not supporting CAG is rejected due to CAG restrictions, the network shall reject the mobility and periodic registration update request with a 5GMM cause value other than the 5GMM cause #76 (Not authorized for this CAG or authorized for CAG cells only).