Question: Over the Wd reference point in a 3GPP system to Wireless Local Area Network (WLAN) interworking scenario, which protocol combinations are supported by both the 3GPP AAA Proxy and the 3GPP AAA Server?
Option 1: Only RADIUS with specified extensions
Option 2: Both RADIUS with specified extensions and Diameter Base with additional applications (e.g., NASREQ, EAP transport)
Option 3: Either RADIUS or Diameter Base exclusively, without any extensions
Option 4: Neither RADIUS nor Diameter Base; another protocol is used
Explanation: Both the 3GPP AAA Proxy and the 3GPP AAA Server support two protocols over the Wd reference point: RADIUS with specific extensions (for EAP frame transport, public WLAN identification, etc.) and Diameter Base with additional applications like NASREQ for accounting and EAP transport, ensuring flexibility and compatibility with various WLAN AN characteristics.