Method for interaction between layers in wireless communication system and apparatus therefor

A user equipment (UE) configured to operate in a wireless communication system, the UE comprising:

• a transceiver;
• at least one processor;
• and
• at least one computer memory operably connectable to the at least one processor and storing instructions that, when executed by the at least one processor, perform operations comprising:
• transmitting, via the transceiver to an access and mobility management function (AMF), an uplink (UL) non-access stratum (NAS) message that comprises a session management (SM) message;
• receiving, via the transceiver from the AMF, a downlink (DL) NAS message that comprises a cause value indicating that the SM message was not forwarded due to routing failure;
• and
• transferring, from a lower sublayer of the UE to an upper sublayer of the UE, an indication that the SM message was not forwarded due to routing failure, based on the cause value,
• wherein the SM message is generated in the upper sublayer of the UE and is provided to the lower sublayer of the UE, and
• wherein the UL NAS message comprising the SM message is sent to the AMF by the lower sublayer of the UE.