This example describes the notification of a UE that occurs when the S-CSCF
assigned to that user requests re-authentication.
It is assumed that user has registered and also subscribed to the registration state event before.
After this procedure the user's UE might automatically initiate re-registration procedures.
If the user fails to re-register,
the public user identity may be
deregistered by S-CSCF.
The network initiated re-authentication event for the private user identity of the user occurs at the S-CSCF.
As the user has subscribed to the registration state event package this is the trigger point for the
S-CSCF to notify the user about the event occurrence. For simplicity, the NOTIFY request towards the
P-CSCF is not shown.