Question: In a UE-initiated IPsec tunnel setup for non-3GPP accesses, what authentication method is specified for User Equipment (UE) authentication within the IKEv2 protocol?
Option 1: Public key signature based authentication with certificates
Option 2: EAP-AKA (Extensible Authentication Protocol Method for UMTS Authentication and Key Agreement) within IKEv2
Option 3: Pre-Shared Key (PSK) authentication as defined in RFC 5996
Option 4: Username and Password combination via IKEv2 ID_USER payload
Explanation: EAP-AKA is specifically mentioned for UE authentication within the context of IKEv2 for setting up IPsec tunnels. This method leverages the UMTS authentication and key agreement protocol adapted for use in EAP, ensuring secure authentication of UEs in non-3GPP access scenarios. Public key signature with certificates is used for ePDG (Evolved Packet Data Gateway) authentication, not UE authentication. PSK and Username/Password combinations are not specified in the provided context for UE authentication in this scenario.