Method for PDU session establishment procedure and AMF node

An access and mobility management function (AMF) entity configured to handle a packet data unit (PDU) session establishment procedure, the AMF entity 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, cause the at least one processor to perform operations comprising:
• receiving, from a user equipment (UE), a PDU session establishment request including an identifier of an existing PDU session;
• obtaining a session management function (SMF) identifier corresponding to the identifier of the existing PDU session;
• determining, based on the SMF identifier, whether to reject the PDU session establishment request;
• and
• based on a determination to reject the PDU session establishment request, transmitting a message comprising a rejection cause to the UE,
• wherein determining, based on the SMF identifier, whether to reject the PDU session establishment request comprises:
• based on a determination that a SMF entity corresponding to the SMF identifier and the AMF entity belong to a same Public Land Mobile Network (PLMN), determining not to reject the PDU session establishment request.

A method for handling a packet data unit (PDU) session establishment procedure, performed by a user equipment (UE), the method comprising:

• transmitting, to an access and mobility management function (AMF) entity, a PDU session establishment request including an identifier of an existing PDU session,
• wherein the identifier of the existing PDU session is used by the AMF entity to obtain a session management function (SMF) identifier, and
• wherein the SMF identifier is used by the AMF entity to determine whether to reject the PDU session establishment request;
• and
• receiving a message comprising a rejection cause, based on that the AMF entity determines to reject the PDU session establishment request,
• wherein the message comprising the rejection cause is not received, based on that the AMF entity determines that a SMF entity, corresponding to the SMF identifier, and the AMF entity belong to a same Public Land Mobile Network (PLMN).