Question: In a Trusted WLAN Access Network (TWAN) interfaced with the Evolved Packet Core (EPC), where does the authenticator reside for authentication and key agreement processes?
Option 1: In the 3GPP AAA Server/Proxy
Option 2: In the PDN Gateway (PDN GW)
Option 3: In the User Equipment (UE)
Option 4: In the Trusted WLAN Access Network (TWAN) itself
Explanation: The correct placement of the authenticator in a TWAN setup is crucial for security. By residing in the TWAN, the authenticator can effectively manage authentication and key agreement directly within the trusted non-3GPP access network, ensuring secure connectivity to the EPC. This localized management enhances the integrity and confidentiality of the network, aligning with security contexts based on key derivatives.