Question: Over Gx Reference Point, what information is transported when a Trusted S2c is used in a WLAN scenario and NAT is detected, specifically for user plane traffic encapsulated by IPSec?
Option 1: UE Local IP Address, P-GW IP Address, and TCP Source Port Number of DSMIPv6 Binding Update Signalling
Option 2: H(e)NB Local IP Address, UDP Source Port Number of IPSec Tunnel, and Serving Gateway IP Address
Option 3: UE Local IP Address, S-GW IP Address, and ICMP Identifier for NAT Traversal
Option 4: UE Local IP Address, UDP Source Port Number of IPSec Tunnel, UDP Source Port Number of DSMIPv6 Binding Update Signalling, and P-GW IP Address
Explanation: In a WLAN scenario using Trusted S2c, when NAT is detected and user plane traffic is encapsulated by IPSec, the Gx reference point transports specific parameters to ensure proper connectivity. These include the UE's local IP address (for endpoint identification), the UDP source port number of the IPSec tunnel (for secure traversal through NAT), the UDP source port number of DSMIPv6 binding update signalling (to manage mobility without encapsulating user plane traffic by IPSec in this context, but relevant for overall session management), and the P-GW IP address (the gateway to the public internet or another network). This combination ensures that both security (via IPSec) and mobility management (via DSMIPv6) aspects are covered.