Question: For non-3GPP access in EPS, what are the specified authentication protocols, and where must their respective EAP servers be located?
Option 1: EAP-SIM, with the EAP server in the User Equipment (UE)
Option 2: EAP-AKA or EAP-AKA', with the 3GPP AAA server in the EPC
Option 3: PAP and CHAP, with servers in external networks for non-3GPP access
Option 4: EAP-TLS, with the server location not specified
Explanation: For non-3GPP accesses in EPS, access authentication must be based on either EAP-AKA or EAP-AKA'. Critically, the EAP server for both must reside in the 3GPP AAA server located within the Evolved Packet Core (EPC), ensuring robust security and interoperability.