Question: During mobility events in a non-3GPP access (e.g., I-WLAN 3GPP IP Access System), what determines when a source ePDG (Evolved Packet Data Gateway) may delete a UE's (User Equipment) IPsec tunnel security association parameters if the UE moves out of coverage?
Option 1: Upon receiving a direct notification from the UE indicating its departure.
Option 2: After a specified timeout period, following repeated unsuccessful attempts to contact the UE, as per RFC 5996 guidelines.
Option 3: Immediately upon detecting the UE's handover to a different access type (e.g., from I-WLAN to 3GPP).
Option 4: Once the UE's IPsec tunnel security association parameters naturally expire due to lifetime expiration.
Explanation: According to the described handling of IPsec tunnels in mobility events, if after repeated attempts to contact the UE, the source ePDG concludes that the UE has failed to respond for a timeout period (as specified in RFC 5996), it may then delete all the UE's IPsec tunnel SA parameters. This approach ensures resources are freed when communication is deemed unsuccessful due to the UE's absence from the coverage area, without relying on immediate notifications or waiting for natural parameter expiration.