Processing NSSAA failure caused by network error or timeout

An Access and mobility Management Function (AMF) adapted to operate in a wireless communication system, the AMF comprising:

• at least one processor;
• and
• at least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform operations comprising:
• receiving a registration request message from a User Equipment (UE),
• wherein the registration request message includes requested Network Slice Selection Assistance Information (NSSAI) corresponding to a network slice to which the UE intends to register with, and
• wherein the requested NSSAI contains Single NSSAI (S-NSSAI);
• initiating a Network Slice-Specific Authentication and Authorization (NSSAA) procedure for the S-NSSAI,
• wherein the NSSAA procedure is performed with a Network Slice-Specific Authentication and Authorization Function (NSSAAF);
• receiving a response with HyperText Transfer Protocol (HTTP) status code “504 Gateway Timeout” from the NSSAAF and/or not receiving a response for the NSSAA procedure from the NSSAAF,
• wherein the HTTP status code “504 Gateway Timeout” is received based on an Authentication, Authorization and Accounting Server (AAA-S) being involved in the NSSAA procedure while there is no expected response from the AAA-S in case of timeout, with a message body containing a ProblemDetails structure with a cause attribute set to “TIMED_OUT_REQUEST”;
• and
• based on the NSSAA procedure being unable to be completed due to receiving the response with the HTTP status code “504 Gateway Timeout,” re-initiating the NSSAA procedure after waiting for certain time.

A method performed by a User Equipment (UE) adapted to operate in a wireless communication system, the method comprising:

• transmitting a registration request message to an Access and Mobility Management Function (AMF),
• wherein the registration request message includes requested Network Slice Selection Assistance Information (NSSAI) corresponding to a network slice to which the UE intends to register with, and
• wherein the requested NSSAI contains Single NSSAI (S-NSSAI);
• and
• receiving a registration accept message from the AMF,
• wherein a Network Slice-Specific Authentication and Authorization (NSSAA) procedure for the S-NSSAI is initiated by an Access and mobility Management Function (AMF),
• wherein the NSSAA procedure is performed with a Network Slice-Specific Authentication and Authorization Function (NSSAAF);
• wherein a response with a HyperText Transfer Protocol (HTTP) status code “504 Gateway Timeout” is received by the AMF from the NSSAAF,
• wherein the HTTP status code “504 Gateway Timeout” is received based on an Authentication, Authorization and Accounting Server (AAA-S) being involved in the NSSAA procedure while there is no expected response from the AAA-S in case of timeout, with a message body containing a ProblemDetails structure with a cause attribute set to “TIMED_OUT_REQUEST,” and
• wherein, based on the NSSAA procedure being unable to be completed due to receiving the response with the HTTP status code “504 Gateway Timeout”, the NSSAA procedure is re-initiated after waiting for certain time.