6.4.2.4.3 Handling of network rejection not due to congestion control

If the 5GSM cause value is different from #26 "insufficient resources", #37 "5GS QoS not accepted", #44 "Semantic errors in packet filter(s)", #45 "Syntactical error in packet filter(s)", #46 "out of LADN service area", #59 "unsupported 5QI value", #67 "insufficient resources for specific slice and DNN", #69 "insufficient resources for specific slice", #83 "Semantic error in the QoS operation", and #84 "Syntactical error in the QoS operation", and the Back-off timer value IE is included, the UE shall behave as follows: (if the UE is a UE configured for high priority access in selected PLMN or SNPN, exceptions are specified in clause 6.2.12):

• if the timer value indicates neither zero nor deactivated and:
• if the UE provided DNN and S-NSSAI to the network during the PDU session establishment, the UE shall start the back-off timer with the value provided in the Back-off timer value IE for the PDU session modification procedure and:
• in a PLMN, [PLMN, DNN, (mapped) HPLMN S-NSSAI of the PDU session] combination. The UE shall not send another PDU SESSION MODIFICATION REQUEST message with exception of those identified in clause 6.4.2.1, for the same DNN and the (mapped) HPLMN S-NSSAI of the PDU session in the current PLMN, until the back-off timer expires, the UE is switched off, or the USIM is removed; or
• in an SNPN, [SNPN, selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, (mapped) subscribed SNPN S-NSSAI] combination. The UE shall not send another PDU SESSION MODIFICATION REQUEST message with exception of those identified in clause 6.4.2.1, for the same DNN and (mapped) subscribed SNPN S-NSSAI of the PDU session in the current SNPN using the selected entry of the "list of subscriber data" or selected PLMN subscription, until the back-off timer expires, the UE is switched off, the USIM is removed, or the selected entry of the "list of subscriber data" is updated;
• if the UE did not provide a DNN or S-NSSAI or any of the two parameters to the network during the PDU session establishment, it shall start the back-off timer accordingly for the PDU session modification procedure and:
• in a PLMN, [PLMN, DNN, no S-NSSAI], [PLMN, no DNN, (mapped) HPLMN S-NSSAI of the PDU session] or [PLMN, no DNN, no S-NSSAI] combination. Dependent on the combination, the UE shall not send another PDU SESSION MODIFICATION REQUEST message with exception of those identified in clause 6.4.2.1, for the same [PLMN, DNN, no S-NSSAI], [PLMN, no DNN, (mapped) HPLMN S-NSSAI of the PDU session] or [PLMN, no DNN, no S-NSSAI] combination in the current PLMN, until the back-off timer expires, the UE is switched off, or the USIM is removed; or
• in an SNPN, [SNPN, selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, no S-NSSAI], [SNPN, selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session] or [SNPN, selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, no S-NSSAI] combination. Dependent on the combination, the UE shall not send another PDU SESSION MODIFICATION REQUEST message with exception of those identified in clause 6.4.2.1, for the same [SNPN, selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, no S-NSSAI], [SNPN, selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session] or [SNPN, selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, no S-NSSAI] combination in the current SNPN, until the back-off timer expires, the UE is switched off, the USIM is removed, or the selected entry in the "list of subscriber data" is updated;
• if the timer value indicates that this timer is deactivated and:
• if the UE provided DNN and S-NSSAI to the network during the PDU session establishment, the UE shall not send another PDU SESSION MODIFICATION REQUEST message with exception of those identified in clause 6.4.2.1, for:
• in a PLMN, the same DNN and the (mapped) HPLMN S-NSSAI of the PDU session in the current PLMN, until the UE is switched off, or the USIM is removed; or
• in an SNPN, the same DNN and the (mapped) subscribed SNPN S-NSSAI of the PDU session in the current SNPN using the selected entry of the "list of subscriber data" or selected PLMN subscription, until the UE is switched off, or the USIM is removed, or the selected entry in the "list of subscriber data";
• if the UE did not provide a DNN or S-NSSAI or any of the two parameters to the network during the PDU session establishment, the UE shall not send another PDU SESSION MODIFICATION REQUEST message with exception of those identified in clause 6.4.2.1, for:
• in a PLMN; the same [PLMN, DNN, no S-NSSAI], [PLMN, no DNN, (mapped) HPLMN S-NSSAI of the PDU session] or [PLMN, no DNN, no S-NSSAI] combination in the current PLMN, until the UE is switched off, or the USIM is removed; or
• in an SNPN, the same [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, no S-NSSAI], [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session] or [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, no S-NSSAI] combination in the current SNPN using the selected entry of the "list of subscriber data" or selected PLMN subscription, until the UE is switched off, the USIM is removed, or the selected entry in the "list of subscriber data" is updated; and
• if the timer value indicates zero, the UE may send another PDU SESSION MODIFICATION REQUEST message for:
• in a PLMN, the same combination of [PLMN, DNN, (mapped) HPLMN S-NSSAI of the PDU session], [PLMN, DNN, no S-NSSAI], [PLMN, no DNN, (mapped) HPLMN S-NSSAI of the PDU session], or [PLMN, no DNN, no S-NSSAI] in the current PLMN; or
• in an SNPN, the same combination of [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, no S-NSSAI], [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], or [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, no S-NSSAI] in the current SNPN.

If the Back-off timer value IE is not included, then the UE shall ignore the Re-attempt indicator IE provided by the network in the PDU SESSION MODIFICATION REJECT message, if any.

• Additionally, if the 5GSM cause value is #32 "service option not supported", or #33 "requested service option not subscribed", then:
• the UE not operating in SNPN access operation mode shall proceed as follows:
• if the UE is registered in the HPLMN or in a PLMN that is within the EHPLMN list, the UE shall behave as described above in the present clause using the configured SM Retry Timer value as specified in 3GPP TS 24.368 [17] or in USIM file NASCONFIG as specified in 3GPP TS 31.102 [22], if available, as back-off timer value; and

NOTE 1: The way to choose one of the configured SM Retry Timer values for back-off timer value is up to UE implementation if the UE is configured with:- an SM Retry Timer value in the ME as specified in 3GPP TS 24.368 [17]; and- an SM Retry Timer value in USIM file NASCONFIG as specified in 3GPP TS 31.102 [22].

• otherwise, if the UE is not registered in its HPLMN or in a PLMN that is within the EHPLMN list, or if the SM Retry Timer value is not configured, the UE shall behave as described above in the present clause, using the default value of 12 minutes for the back-off timer; or
• the UE operating in SNPN access operation mode shall proceed as follows:
• if:

A) the SM Retry Timer value for the current SNPN as specified in 3GPP TS 24.368 [17] is available; or

B) the SM Retry Timer value in USIM file NASCONFIG as specified in 3GPP TS 31.102 [22] is available and the UE used the USIM for registration to the current SNPN;

then the UE shall behave as described above in the present clause using the configured SM Retry Timer value as back-off timer value; or

NOTE 2: The way to choose one of the configured SM Retry Timer values for back-off timer value is up to UE implementation if both conditions in bullets A) and B) above are satisfied.

• otherwise, the UE shall behave as described above in the present clause, using the default value of 12 minutes for the back-off timer.
• For 5GSM cause values different from #32 "service option not supported", or #33 "requested service option not subscribed", the UE behaviour regarding the start of a back-off timer is specified in clause 6.2.12.

The UE shall not stop any back-off timer:

• upon a PLMN or SNPN change;
• upon an inter-system change; or
• upon registration over another access type.

If the network indicates that a back-off timer for the PDU session modification procedure is deactivated, then it remains deactivated:

• upon a PLMN or SNPN change;
• upon an inter-system change; or
• upon registration over another access type.

NOTE 3: This means the back-off timer can still be running or be deactivated for the given 5GSM procedure when the UE returns to the PLMN or SNPN or when it performs inter-system change back from S1 mode to N1 mode. Thus the UE can still be prevented from sending another PDU SESSION MODIFICATION REQUEST message for the combination of [PLMN, DNN, (mapped) HPLMN S-NSSAI of the PDU session], [PLMN, DNN, no S-NSSAI], [PLMN, no DNN, (mapped) HPLMN S-NSSAI of the PDU session], or [PLMN, no DNN, no S-NSSAI] in the PLMN, or for the combination of [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, (mapped) subscribed S-NSSAI], [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, no S-NSSAI], [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, (mapped) subscribed S-NSSAI], or [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, no S-NSSAI] in the SNPN.

If the back-off timer is started upon receipt of a PDU SESSION MODIFICATION REJECT (i.e. the timer value was provided by the network, a configured value is available or the default value is used as explained above) or the back-off timer is deactivated, the UE behaves as follows:

• after a PLMN or SNPN change the UE may send a PDU SESSION MODIFICATION REQUEST message for:
• in a PLMN, the combination of [new PLMN, DNN, (mapped) HPLMN S-NSSAI of the PDU session], [new PLMN, DNN, no S-NSSAI], [new PLMN, no DNN, (mapped) HPLMN S-NSSAI of the PDU session], or [new PLMN, no DNN, no S-NSSAI] in the new PLMN, if the back-off timer is not running and is not deactivated for the PDU session modification procedure and the combination of [new PLMN, DNN, (mapped) HPLMN S-NSSAI of the PDU session], [new PLMN, DNN, no S-NSSAI], [new PLMN, no DNN, (mapped) HPLMN S-NSSAI of the PDU session], or [new PLMN, no DNN, no S-NSSAI]; or
• in an SNPN, the combination of [new SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], [new SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, no S-NSSAI], [new SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], or [new SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, no S-NSSAI] in the new SNPN, if the back-off timer is not running and is not deactivated for the PDU session modification procedure and the combination of [new SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], [new SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, no S-NSSAI], [new SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], or [new SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, no S-NSSAI];

Furthermore, as an implementation option, for the 5GSM cause value #32 "service option not supported" or #33 "requested service option not subscribed", if the network does not include a Re-attempt indicator IE, the UE may decide not to automatically send another PDU SESSION MODIFICATION REQUEST message:

• in a PLMN, the same combination of [PLMN, DNN, (mapped) HPLMN S-NSSAI of the PDU session], [PLMN, DNN, no S-NSSAI], [PLMN, no DNN, (mapped) HPLMN S-NSSAI of the PDU session], or [PLMN, no DNN, no S-NSSAI], if the UE is registered to a new PLMN which is in the list of equivalent PLMNs; or
• in an SNPN, if the UE supports equivalent SNPNs, the same combination of [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, no S-NSSAI], [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], or [SNPN, the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, no S-NSSAI], if the UE is registered to a new SNPN which is in the list of equivalent SNPNs.
• if the network does not include the Re-attempt indicator IE to indicate whether re-attempt in S1 mode is allowed, or the UE ignores the Re-attempt indicator IE, e.g. because the Back-off timer value IE is not included, then:
• if the UE is registered in its HPLMN or in a PLMN that is within the EHPLMN list and the back-off timer is running for the combination of [PLMN, DNN, (mapped) HPLMN S-NSSAI of the PDU session] or [PLMN DNN, no S-NSSAI], the UE shall apply the configured SM_RetryAtRATChange value as specified in 3GPP TS 24.368 [17] or in USIM file NASCONFIG as specified in 3GPP TS 31.102 [22], if available, to determine whether the UE may attempt an EPS bearer resource allocation procedure or an EPS bearer resource modification procedure for the same [PLMN, DNN] combination in S1 mode; and

NOTE 4: The way to choose one of the configured SM_RetryAtRATChange values for back-off timer value is up to UE implementation if the UE is configured with:- an SM_RetryAtRATChange value in ME as specified in 3GPP TS 24.368 [17]; and- an SM_RetryAtRATChange value in USIM file NASCONFIG as specified in 3GPP TS 31.102 [22].

• if the UE is not registered in its HPLMN or in a PLMN that is within the EHPLMN list, or if the NAS configuration MO as specified in 3GPP TS 24.368 [17] is not available and the value for inter-system change is not configured in the USIM file NASCONFIG, then the UE behaviour regarding an EPS bearer resource allocation procedure or an EPS bearer resource modification procedure for the same [PLMN, DNN] combination in S1 mode is unspecified; and
• if the network includes the Re-attempt indicator IE indicating that re-attempt in an equivalent PLMN or equivalent SNPN is not allowed, then depending on the timer value received in the Back-off timer value IE, for:
• in a PLMN, each combination of a PLMN from the equivalent PLMN list and the respective [DNN, (mapped) HPLMN S-NSSAI of the PDU session], [DNN, no S-NSSAI], [no DNN, (mapped) HPLMN S-NSSAI of the PDU session], or [no DNN, no S-NSSAI] combination, the UE shall start a back-off timer for the PDU session modification procedure with the value provided by the network, or deactivate the respective back-off timer as follows:
• if the Re-attempt indicator IE additionally indicates that re-attempt in S1 mode is allowed, the UE shall start or deactivate the back-off timer for N1 mode only; and
• otherwise, the UE shall start or deactivate the back-off timer for S1 and N1 mode
• in a SNPN, if the UE supports equivalent SNPNs, each combination of a SNPN from the equivalent SNPN list and the respective [the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], [the selected entry of the "list of subscriber data" or selected PLMN subscription, DNN, no S-NSSAI], [the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, (mapped) subscribed SNPN S-NSSAI of the PDU session], or [the selected entry of the "list of subscriber data" or selected PLMN subscription, no DNN, no S-NSSAI] combination, the UE shall start a back-off timer for the PDU session modification procedure with the value provided by the network, or deactivate the respective back-off timer, for N1 mode in an SNPN.

If the back-off timer for a [PLMN, DNN] or [PLMN, no DNN] combination was started or deactivated in S1 mode upon receipt of BEARER RESOURCE ALLOCATION REJECT message or BEARER RESOURCE MODIFICATION REJECT message (see 3GPP TS 24.301 [15]) and the network indicated that re-attempt in N1 mode is allowed, then this back-off timer does not prevent the UE from sending a PDU SESSION MODIFICATION REQUEST message in this PLMN for the same DNN after inter-system change to N1 mode. If the network indicated that re-attempt in N1 mode is not allowed, the UE shall not send any PDU SESSION MODIFICATION REQUEST message with exception of those identified in clause 6.4.2.1, in this PLMN for the same DNN in combination with any S-NSSAI or without S-NSSAI, after inter-system change to N1 mode until the timer expires, the UE is switched off or the USIM is removed.

NOTE 5: The back-off timer is used to describe a logical model of the required UE behaviour. This model does not imply any specific implementation, e.g. as a timer or timestamp.

NOTE 6: Reference to back-off timer in this section can either refer to use of timer T3396 or to use of a different packet system specific timer within the UE. Whether the UE uses T3396 as a back-off timer or it uses different packet system specific timers as back-off timers is left up to UE implementation.

If the 5GSM cause value is #46 "out of LADN service area", the UE shall ignore the Back-off timer value IE and Re-attempt indicator IE provided by the network, if any. If the UE is not located inside the LADN service area, the UE shall not send another PDU SESSION MODIFICATION REQUEST message except for indicating a change of 3GPP PS data off UE status or another PDU SESSION ESTABLISHMENT REQUEST message for the LADN DNN provided by the UE during the PDU session establishment procedure until the LADN information for the specific LADN DNN or the extended LADN information for the specific LADN DNN and S-NSSAI is updated as described in clause 5.4.4 and clause 5.5.1. If the UE is not located inside the LADN service area, the UE shall not indicate the PDU session(s) for the LADN DNN provided by the UE during the PDU session establishment procedure in the Uplink data status IE included in the SERVICE REQUEST message until the LADN information for the specific LADN DNN or the extended LADN information for the specific LADN DNN and S-NSSAI is provided by network as described in clause 5.4.4 and clause 5.5.1.

NOTE 7: Based on UE implementation, the UE locating inside the LADN service area can send another PDU SESSION ESTABLISHMENT REQUEST message or PDU SESSION MODIFICATION REQUEST message for the LADN DNN which was rejected with the 5GSM cause value #46 "out of LADN service area".

NOTE 7A: If the UE does not receive a CONFIGURATION UPDATE COMMAND message with new LADN information within an implementation dependent time, the UE can request this information by initiating a registration procedure for mobility or periodic registration update (see clause 5.5.1.3.2, item q).

If the 5GSM cause value is #87 "QoS differentiation for non-3GPP device identifier(s) not available", the UE shall ignore the Back-off timer value IE and Re-attempt indicator IE provided by the network, if any. The UE should pass the corresponding error cause to the upper layers.

NOTE 7B: On receiving 5GSM cause value #87, upper layers can provide the UE with a list of available non-3GPP device information to trigger another UE-requested PDU session modification procedure.

If the 5GSM cause value is #37 "5GS QoS not accepted", #44 "Semantic errors in packet filter(s)", #45 "Syntactical error in packet filter(s)", #59 "unsupported 5QI value", #83 "Semantic error in the QoS operation" or #84 "Syntactical error in the QoS operation", the UE shall ignore the Back-off timer value IE and Re-attempt indicator IE provided by the network, if any. The UE should pass the corresponding error cause to the upper layers.

NOTE 8: How to solve the issues of not accepted 5GS QoS and unsupported 5QI value in the upper layers is UE implementation specific.