Question: In a 3GPP-EPS or Non-3GPP-EPS access scenario, what does the UDP-Source-Port AVP (AVP Code 2806) contain when a NAT is detected for Untrusted WLAN over S2b access?
Option 1: The TCP destination port number used for the IKEv2 tunnel.
Option 2: The UDP source port number used for the IKEv2 tunnel, as per IETF RFC 3948.
Option 3: The IP address of the ePDG for encapsulation purposes.
Option 4: The UDP source port number utilized for interworking with fixed broadband access networks.
Explanation: In scenarios involving Untrusted WLAN over S2b access where a NAT is detected, the IKEv2 messages between the UE (User Equipment) and the ePDG (Evolved Packet Data Gateway) are encapsulated in UDP messages. According to IETF RFC 3948, this specific configuration requires the use of a UDP source port number for the IKEv2 tunnel, which is precisely what the UDP-Source-Port AVP (AVP Code 2806) contains in such cases.