Question: In a 3GPP-compliant network, when is the 'Start of interception for ProSe UE-to-NW Relay' event triggered by the S-GW and PDN-GW, considering a UE's role as a ProSe UE-to-NW Relay for any Remote UE?
Option 1: When a new Remote UE connects to the network through an existing ProSe UE-to-NW Relay.
Option 2: Upon initiation of lawful interception on a UE already acting as a ProSe UE-to-NW Relay, or during S-GW change due to relay mobility.
Option 3: When the ProSe UE-to-NW Relay handovers from one eNodeB to another without changing S-GW.
Option 4: After a successful security key exchange between the Remote UE and the network via the ProSe UE-to-NW Relay.
Explanation: This is correct because the event in question is triggered under two conditions: (1) when interception is initiated on a UE already serving as a ProSe UE-to-NW Relay for any Remote UE, and (2) during a change of S-GW due to mobility of the ProSe UE-to-NW Relay, ensuring effective lawful interception management across network changes and specific UE roles.