When the Network Initiated Deregistration Event occurs in S-CSCF1, S-CSCF1 informs the HSS
that the user is no longer registered. S-CSCF1 either notifies the HSS to clear or requests to keep its
location information for that subscriber. The HSS then either clears or keeps S-CSCF1 name for that
subscriber according to request. In case S-CSCF1 location information is cleared from the HSS, the
state of the subscriber identity is stored as "not registered" in the HSS. In case S-CSCF1 location
information is kept in the HSS, the state of the subscriber identity is stored as "unregistered" in the HSS
and S-CSCF1. The HSS acknowledges the request.