Section: 5.17.2.5 Secondary DN authentication and authorization in EPS Interworking case
Content: Secondary authentication/authorization by a DN-AAA server during the establishment of a PDN connection over 3GPP access to EPC, is supported based on following principles: - It is optional for the UE to support EAP-based secondary authentication and authorization by DN-AAA over EPC, - A SMF+PGW-C shall be used to serve DNN(s) requiring secondary authentication/authorization by a DN-AAA server, - For secondary authentication/authorization by a DN-AAA server, the SMF+PGW-C runs the same procedures with PCF, UDM and DN-AAA and uses the same corresponding interfaces regardless of whether the UE is served by EPS or 5GS, - The interface towards the UE is different (usage of NAS for EPS instead of NAS for 5GS) between the EPS and 5GS cases. This is further specified in Annex H of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]. In this Release, EAP based Secondary authentication by a DN-AAA server during the establishment of a PDN connection over non-3GPP access to EPC is not supported.