Question: In the context of Evolved Packet Core (EPC) and non-3GPP access interworking system, what indicates a successful tunnel establishment in terms of message transmission between network elements?
Option 1: Transmission of tunnel establishment request message from UE to ePDG
Option 2: Transmission of tunnel establishment response message from ePDG to UE
Option 3: Receipt of tunnel establishment reject message by the UE
Option 4: Initiation of EPS bearer resource allocation
Explanation: A successful tunnel establishment is confirmed when the network element responsible for managing the tunnel (the ePDG - Evolved Packet Data Gateway) responds to the User Equipment (UE) with a positive acknowledgement. This is technically represented by the transmission of a tunnel establishment response message from the ePDG to the UE, signifying that the tunnel has been successfully established, ensuring secure and reliable data transfer between the UE and the network via non-3GPP access.