Section: 5.3.1.2 Re-establishment of the N1 NAS signalling connection
Content: When the UE in 5GMM-CONNECTED mode over 3GPP access receives a fallback indication from lower layers, and the UE has no pending NAS procedure and no pending uplink user data for PDU session(s) with user-plane resources already established, the UE shall: a) enter 5GMM-IDLE mode; and b) initiate the registration procedure for mobility and periodic registration update and include the Uplink data status IE in the REGISTRATION REQUEST message indicating the PDU session(s) for which user-plane resources were active prior to receiving the fallback indication, if any (see subclause 5.5.1.3 for further details). When the UE in 5GMM-CONNECTED mode over 3GPP access receives a fallback indication from lower layers, and the UE has pending uplink user data for PDU session(s) with user-plane resources already established but no pending NAS procedure, the UE shall: a) enter 5GMM-IDLE mode; and b) initiate the service request procedure and include the Uplink data status IE in the SERVICE REQUEST message or the CONTROL PLANE SERVICE REQUEST message indicating the PDU session(s) for which user-plane resources were active prior to receiving the fallback indication (see subclause 5.6.1 for further details). When the UE in 5GMM-CONNECTED mode over 3GPP access receives a fallback indication from lower layers, and the UE has a pending registration procedure, a service request procedure, or a de-registration procedure, the UE shall: a) enter 5GMM-IDLE mode; b) proceed with the pending procedure; and c) if the pending procedure is a service request or registration procedure and the SERVICE REQUEST message, the CONTROL PLANE SERVICE REQUEST message or the REGISTRATION REQUEST message does not include UE request type IE with Request type value set to "NAS signalling connection release", the UE shall include the Uplink data status IE in the SERVICE REQUEST message, the CONTROL PLANE SERVICE REQUEST message, or in the REGISTRATION REQUEST message, indicating the PDU session(s) for which user-plane resources were not active prior to receiving a fallback indication from the lower layers and the UE has pending user data to be sent over 3GPP access, if any, and the PDU session(s) for which user-plane resources were active prior to receiving the fallback indication, if any (see subclauses 5.5.1.3 and 5.6.1 for further details). When the UE in 5GMM-CONNECTED mode over 3GPP access receives a fallback indication from lower layers, and the UE has a pending NAS procedure other than a registration procedure, a service request procedure, or a de-registration procedure, the UE shall: a) enter 5GMM-IDLE mode; b) initiate the service request procedure and include the Uplink data status IE in the SERVICE REQUEST message or the CONTROL PLANE SERVICE REQUEST message indicating the PDU session(s) for which user-plane resources were active prior to receiving the fallback indication, if any (see subclause 5.6.1 for further details); and c) upon successful service request procedure completion, proceed with any pending procedure. When the UE in 5GMM-CONNECTED mode over 3GPP access receives a fallback indication from lower layers, and the UE has no pending NAS procedure and no pending uplink user data for PDU session(s) with user-plane resources already established, and the UE was using network resources for 5G ProSe direct discovery over PC5 or 5G ProSe direct communication over PC5 (see 3GPP TS 23.304[ Proximity based Services (ProSe) in the 5G System (5GS) ]  [6E]), the UE shall: a) enter 5GMM-IDLE mode; and b) initiate the service request procedure and include the Uplink data status IE in the SERVICE REQUEST message or the CONTROL PLANE SERVICE REQUEST message indicating the PDU session(s) for which user-plane resources were active prior to receiving the fallback indication, if any (see subclause 5.6.1 for further details). The UE which supports S-NSSAI location validity information, and which has received S-NSSAI location validity information from the AMF, shall include the Uplink data status IE in the REGISTRATION REQUEST message, the SERVICE REQUEST message, or the CONTROL PLANE SERVICE REQUEST message, to indicate the PDU session(s) for which user-plane resources were active prior to receiving the fallback indication, as described above, only if the UE is inside the NS-AoS with respect to the S-NSSAI which is associated with a PDU session. The cases above apply when the UE is in an allowed area or when the UE is not in a non-allowed area. When the UE: a) is in a non-allowed area or is not in an allowed area; b) is in 5GMM-CONNECTED mode over 3GPP access; c) receives a fallback indication from lower layers; and d) does not have signalling pending, the UE shall: a) enter 5GMM-IDLE mode; and b) initiate the registration procedure for mobility and periodic registration update. The UE shall not include the Uplink data status IE in the REGISTRATION REQUEST message except if the PDU session for which user-plane resources were active is an emergency PDU session, or if the UE is configured for high priority access in selected PLMN or SNPN. In the above cases when the UE receives a fallback indication from lower layers, if the UE is in non-allowed area or not in allowed area, the UE shall behave as specified in subclause 5.3.5.