The network-initiated liveness check procedure enables the N3IWF for untrusted non-3GPP access and the TNGF for trusted non-3GPP access to detect whether the UE is alive.
If the N3IWF for untrusted non-3GPP access and the TNGF for trusted non-3GPP access has not received any cryptographically protected IKEv2 or IPsec message for the duration of the timeout period for liveness check selected according to the local policy, the N3IWF for untrusted non-3GPP access and the TNGF for trusted non-3GPP access shall send an INFORMATIONAL request with no payloads
RFC 7296.
The UE shall handle the INFORMATIONAL request with no payloads as per
RFC 7296 and shall send an INFORMATIONAL response.
If an INFORMATIONAL response is received, the N3IWF for untrusted non-3GPP access and the TNGF for trusted non-3GPP access shall consider the liveness check procedure as successfully completed.
If an INFORMATIONAL response is not received, the N3IWF for untrusted non-3GPP access and the TNGF for trusted non-3GPP access shall deem the IKEv2 security association to have failed.
The N3IWF for untrusted non-3GPP access and the TNGF for trusted non-3GPP access shall discard all states associated with the IKE SA and any child SAs that were negotiated using that IKE SA as specified in
RFC 7296. In addition, the N3IWF for untrusted non-3GPP access and the TNGF for trusted non-3GPP access shall inform the AMF that the access stratum connection has been released.