School of Specs 24.501v20.0.0

3GPP 24.501 v20.0.0 — the document's own text

5.6.1.4.1 UE is not using 5GS services with control plane CIoT 5GS optimization

Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).

For cases other than h) in clause 5.6.1.1, the UE shall treat the reception of the SERVICE ACCEPT message as successful completion of the procedure. The UE shall reset the service request attempt counter, stop timer T3517 and enter the state 5GMM-REGISTERED.

For case h) in clause 5.6.1.1,

  • the UE shall treat the indication from the lower layers when the UE has changed to S1 mode or E-UTRA connected to 5GCN (see 3GPP TS 23.502 [9]) as successful completion of the procedure and stop timer T3517;
  • if a UE operating in single-registration mode has changed to S1 mode, it shall disable the N1 mode capability for 3GPP access (see clause 4.9.2); and
  • the AMF shall not check for CAG restrictions.

If the PDU session status information element is included in the SERVICE REQUEST message, then:

  • for single access PDU sessions, the AMF shall:
    • perform a local release of all those PDU sessions which are not in 5GSM state PDU SESSION INACTIVE on the AMF side associated with the access type the SERVICE REQUEST message is sent over, but are indicated by the UE as being in 5GSM state PDU SESSION INACTIVE; and
    • request the SMF to perform a local release of all those PDU sessions. If any of those PDU sessions is associated with one or more multicast MBS sessions, the SMF shall consider the UE as removed from the associated multicast MBS sessions; and
  • for MA PDU sessions, the AMF shall:
    • for MA PDU sessions having user plane resources established in the AMF only on the access the SERVICE REQUEST message is sent over, but are indicated by the UE as no user plane resources established:
      • for all those MA PDU sessions without a PDN connection established as a user-plane resource, perform a local release of all those MA PDU sessions and request the SMF to perform a local release of all those MA PDU sessions. If the MA PDU session is associated with one or more multicast MBS sessions, the SMF shall consider the UE as removed from the associated multicast MBS sessions; and
      • for all those MA PDU sessions with a PDN connection established as a user-plane resource, perform a local release of user plane resources of all those PDU sessions on the access the SERVICE REQUEST message is sent over and request the SMF to perform a local release of user plane resources of all those PDU sessions on the access type the SERVICE REQUEST message is sent over; and
    • for MA PDU sessions having user plane resources established on both accesses in the AMF, but are indicated by the UE as no user plane resources established:
      • perform a local release of user plane resources of all those PDU sessions on the access the SERVICE REQUEST message is sent over; and
      • request the SMF to perform a local release of user plane resources of all those PDU sessions on the access type the SERVICE REQUEST message is sent over. If the SERVICE REQUEST message is sent over 3GPP access and the MA PDU session is associated with one or more multicast MBS sessions, the SMF shall consider the UE as removed from the associated multicast MBS sessions.

If the AMF needs to initiate PDU session status synchronization or a PDU session status IE was included in the SERVICE REQUEST message, the AMF shall include a PDU session status IE in the SERVICE ACCEPT message to indicate:

  • which single access PDU sessions associated with the access type the SERVICE ACCEPT message is sent over are not in 5GSM state PDU SESSION INACTIVE in the AMF; and
  • which MA PDU sessions are not in 5GSM state PDU SESSION INACTIVE and having user plane resources established in the AMF on the access the SERVICE ACCEPT message is sent over.

If the PDU session status information element is included in the SERVICE ACCEPT message, then:

  • for single access PDU sessions, the UE shall perform a local release of all those PDU sessions which are not in 5GSM state PDU SESSION INACTIVE or PDU SESSION ACTIVE PENDING on the UE side associated with the access type the SERVICE ACCEPT message is sent over, but are indicated by the AMF as in 5GSM state PDU SESSION INACTIVE. If a locally released PDU session is associated with one or more multicast MBS sessions, the UE shall locally leave the associated multicast MBS sessions; and
  • for MA PDU sessions, for all those PDU sessions which are not in 5GSM state PDU SESSION INACTIVE or PDU SESSION ACTIVE PENDING and have user plane resources established on the UE side associated with the access the SERVICE ACCEPT message is sent over, but are indicated by the AMF as no user plane resources established:
    • for MA PDU sessions having user plane resources established only on the access type the SERVICE ACCEPT message is sent over, the UE shall perform a local release of those MA PDU sessions. If a locally released MA PDU session is associated with one or more multicast MBS sessions, the UE shall locally leave the associated multicast MBS sessions; and
    • for MA PDU sessions having user plane resources established on both accesses, the UE shall perform a local release on the user plane resources on the access type the SERVICE ACCEPT message is sent over. If the user plane resources over 3GPP access are released and the MA PDU session is associated with one or more multicast MBS sessions, the UE shall locally leave the associated multicast MBS sessions.

If the Uplink data status IE is included in the SERVICE REQUEST message and the UE is:

  • not in NB-N1 mode; or
  • in NB-N1 mode and the UE does not indicate a request to have user-plane resources established for a number of PDU sessions that exceeds the UE's maximum number of supported user-plane resources;

the AMF shall:

  • indicate the SMF to re-establish the user-plane resources for the corresponding PDU sessions;
  • include the PDU session reactivation result IE in the SERVICE ACCEPT message to indicate the user-plane resources re-establishment result of the PDU sessions for which the UE requested to re-establish the user-plane resources; and
  • determine the UE presence in LADN service area (see clause 6.2.6) and forward the UE presence in LADN service area towards the SMF, if the corresponding PDU session is a PDU session for LADN.

If the Allowed PDU session status IE is included in the SERVICE REQUEST message, the AMF shall:

  • for a 5GSM message from each SMF that has indicated pending downlink signalling only, forward the received 5GSM message via 3GPP access to the UE after the SERVICE ACCEPT message is sent;
  • for each SMF that has indicated pending downlink data only:
    • notify the SMF that reactivation of the user-plane resources for the corresponding PDU session(s) associated with non-3GPP access cannot be performed if the corresponding PDU session ID(s) are not indicated in the Allowed PDU session status IE; and
    • notify the SMF that reactivation of the user-plane resources for the corresponding PDU session(s) associated with non-3GPP access can be performed if:
      • for a UE not in NB-N1 mode, the corresponding PDU session ID(s) are indicated in the Allowed PDU session status IE; or
      • for a UE in NB-N1 mode, the corresponding PDU session ID(s) are indicated in the Allowed PDU session status IE, and the resulting number of PDU sessions with established user-plane resources does not exceed the UE's maximum number of supported user-plane resources;
  • for each SMF that have indicated pending downlink signalling and data:
    • notify the SMF that reactivation of the user-plane resources for the corresponding PDU session(s) associated with non-3GPP access cannot be performed if the corresponding PDU session ID(s) are not indicated in the Allowed PDU session status IE;
    • notify the SMF that reactivation of the user-plane resources for the corresponding PDU session(s) associated with non-3GPP access can be performed if:
      • for a UE not in NB-N1 mode, the corresponding PDU session ID(s) are indicated in the Allowed PDU session status IE; or
      • for a UE in NB-N1 mode, the corresponding PDU session ID(s) are indicated in the Allowed PDU session status IE, and the resulting number of PDU sessions with established user-plane resources does not exceed the UE's maximum number of supported user-plane resources; and
    • discard the received 5GSM message for PDU session(s) associated with non-3GPP access; and
  • include the PDU session reactivation result IE in the SERVICE ACCEPT message to indicate the successfully re-established user-plane resources for the corresponding PDU sessions, if any.

If due to regional subscription restrictions or access restrictions the UE is not allowed to access the TA or due to CAG restrictions the UE is not allowed to access the cell, but the UE has an emergency PDU session established, the AMF may accept the SERVICE REQUEST message and indicate to the SMF to perform a local release of all non-emergency PDU sessions (associated with 3GPP access if it is due to CAG restrictions) and informs the UE via the PDU session status IE in the SERVICE ACCEPT message. The AMF shall not indicate to the SMF to release the emergency PDU session. If the AMF indicated to the SMF to perform a local release of all non-emergency PDU sessions (associated with 3GPP access if it is due to CAG restrictions), the network shall behave as if the UE is registered for emergency services.

If the PDU session reactivation result IE is included in the SERVICE ACCEPT message indicating that the user-plane resources have been successfully reactivated for a PDU session that was indicated by the UE in the Allowed PDU session status IE as allowed to be re-established over 3GPP access, the UE considers the corresponding PDU session to be associated with the 3GPP access. If the user-plane resources of a PDU session have been successfully reactivated over the 3GPP access, the AMF and SMF update the associated access type of the corresponding PDU session.

If the user-plane resources cannot be established for a PDU session, the AMF shall include the PDU session reactivation result IE in the SERVICE ACCEPT message indicating that user-plane resources for the corresponding PDU session cannot be re-established, and:

  • if the user-plane resources cannot be established because the SMF indicated to the AMF that the UE is located out of the LADN service area (see 3GPP TS 29.502 [20A]), the AMF shall include the PDU session reactivation result error cause IE with the 5GMM cause set to #43 "LADN not available";
  • if the user-plane resources cannot be established because the SMF indicated to the AMF that only prioritized services are allowed (see 3GPP TS 29.502 [20A]), the AMF shall include the PDU session reactivation result error cause IE with the 5GMM cause set to #28 "restricted service area";
  • if the user-plane resources cannot be established because the SMF indicated to the AMF that the resource is not available in the UPF (see 3GPP TS 29.502 [20A]), the AMF shall include the PDU session reactivation result error cause IE with the 5GMM cause set to #92 "insufficient user-plane resources for the PDU session";
  • if the user-plane resources cannot be established because the SMF indicated to the AMF that the S-NSSAI associated with the PDU session is unavailable due to NSAC (see 3GPP TS 29.502 [20A]), the AMF shall include the PDU session reactivation result error cause IE with the 5GMM cause set to #69 "insufficient resources for specific slice";
  • if the user-plane resources cannot be established because the AMF determines that the UE is outside the NS-AoS of the S-NSSAI associated with the PDU session, the AMF may include the PDU session reactivation result error cause IE with the 5GMM cause set to #69 "insufficient resources for specific slice" to indicate the cause of failure to re-establish the user-plane resources; or
  • otherwise, the AMF may include the PDU session reactivation result error cause IE to indicate the cause of failure to re-establish the user-plane resources.

NOTE 1: It is up to UE implementation when to re-send a request for user-plane re-establishment for the associated PDU session after receiving a PDU session reactivation result error cause IE with a 5GMM cause set to #92 "insufficient user-plane resources for the PDU session".

NOTE 2: The UE can locally start a back-off timer after receiving a PDU session reactivation result error cause IE with a 5GMM cause set to #69 "insufficient resources for specific slice". The value of the back-off timer is up to UE implementation. Upon expiry of the back-off timer, the UE can re-send a request for user-plane re-establishment for the associated PDU session.

NOTE 3: If the UE that does not support S-NSSAI location validity information is outside the NS-AoS of the S-NSSAI associated with the PDU session, the AMF may perform congestion control and indicate PDU session reactivation result error cause IE with the 5GMM cause set to #69 "insufficient resources for specific slice".

For case a, b and e,

  • if the AMF has a service area list or LADN information which is applicable to the current TAI of the UE and was not yet provided to the UE, before sending the SERVICE ACCEPT message the AMF shall initiate the generic UE configuration update procedure and include the service area list or LADN information or both in the CONFIGURATION UPDATE COMMAND message;
  • if timer T3540 is not started (see clause 5.3.1.3, item f), and the UE did not receive a CONFIGURATION UPDATE COMMAND message during the service request procedure, the UE may initiate a registration procedure for mobility or periodic registration update. If timer T3540 is started and the UE does not receive a CONFIGURATION UPDATE COMMAND message before the established N1 NAS signalling connection is released by the network or timer T3540 expires or is stopped as specified in clause 5.3.1.3, the UE may initiate the registration procedure for mobility or periodic registration update upon release of the N1 NAS signalling connection; and
  • if the AMF has S-NSSAI location validity information that is applicable to the current cell of the UE and was not yet provided to the UE, before sending the SERVICE ACCEPT message the AMF shall initiate the generic UE configuration update procedure and include the S-NSSAI location validity information in the CONFIGURATION UPDATE COMMAND message.

If the PDU session reactivation result IE is included in the SERVICE ACCEPT message indicating that the user-plane resources cannot be established for a PDU session that was indicated by the UE in the Allowed PDU session status IE as allowed to be re-established over 3GPP access, the UE considers the corresponding PDU session to be associated with the non-3GPP access.

If the MUSIM UE does not include the Paging restriction IE in the SERVICE REQUEST message, the AMF shall delete any stored paging restriction for the UE and stop restricting paging.

For case m in clause 5.6.1.1 when the MUSIM UE sets the Request type to "NAS signalling connection release" in the SERVICE REQUEST message, the AMF shall initiate the release of the N1 NAS signalling connection after the completion of the service request procedure.

For cases o and p in clause 5.6.1.1 when the MUSIM UE sets the Request type to "NAS signalling connection release" or to "Rejection of paging" in the UE request type IE in the SERVICE REQUEST message and if the UE requests restriction of paging by including the Paging restriction IE, the AMF:

  • if accepts the paging restriction, shall include the 5GS additional request result IE in the SERVICE ACCEPT message and set the Paging restriction decision to "paging restriction is accepted". The AMF shall store the paging restriction of the UE and enforce these restrictions in the paging procedure as described in clause 5.6.2; or
  • if rejects the paging restriction, shall include the 5GS additional request result IE in the SERVICE ACCEPT message and set the Paging restriction decision to "paging restriction is rejected", and shall discard the received paging restriction. The AMF shall delete any stored paging restriction for the UE and stop restricting paging; and

the AMF shall initiate the release of the N1 NAS signalling connection as follows:

  • for case o in clause 5.6.1.1, after the completion of the service request procedure;
  • for case p in clause 5.6.1.1, after the completion of the generic UE configuration update procedure that is triggered after the completion of the service request procedure.

If the SERVICE REQUEST message is for emergency services fallback, the AMF triggers the emergency services fallback procedure as specified in clause 4.13.4.2 of 3GPP TS 23.502 [9].

If the UE having an emergency PDU session associated with 3GPP access sent the SERVICE REQUEST message via:

  • a CAG cell and none of the CAG-ID(s) of the CAG cell are authorized based on the "Allowed CAG list" for the current PLMN in the UE's subscription; or
  • a non-CAG cell in a PLMN for which the UE's subscription contains an "indication that the UE is only allowed to access 5GS via CAG cells";

the network shall accept the SERVICE REQUEST message and release all non-emergency PDU sessions associated with 3GPP access locally. The emergency PDU session associated with 3GPP access and PDU sessions associated with non-3GPP access shall not be released.

If the AMF received the list of TAIs from the satellite NG-RAN as described in 3GPP TS 23.501 [8], and determines that, by UE subscription and operator's preferences, any but not all TAIs in the received list of TAIs is forbidden for roaming or for regional provision of service, the AMF shall include the TAI(s) in:

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

in the SERVICE ACCEPT message.

NOTE 9: Void.

If the UE receives the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE in the SERVICE ACCEPT message and 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 into the list of "5GS forbidden tracking areas for roaming" and remove the TAI(s) from the stored TAI list if present.

If the UE receives the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for regional provision of service" IE in the SERVICE ACCEPT message and 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 into the list of "5GS forbidden tracking areas for regional provision of service" and remove the TAI(s) from the stored TAI list if present.