Stale sessions

[Stelio Gouveia]

Im using the following configuration to handle sessions

#  Session database, used for checking Simultaneous-Use. Either the radutmp
#  or rlm_sql module can handle this.
#  The rlm_sql module is *much* faster
session {
    #radutmp
    #
    #  See "Simultaneous Use Checking Querie" in sql.conf
    sql
}

My problem is that im getting Access-Reject packet every now and then
(My users are logging in and out correctly... and my NASes are all up
and functioning)
According to this thread
http://lists.freeradius.org/mailman/htdig/freeradius-users/2005-March/042339.html
- radutmp must be enabled
I have noticed that you cant rely on the sql method, even thou there is
a simul_count_query! In my case when i encounter a stale session i set
the AcctStopTime = AcctStartTime + AcctSessionTime. Although this seems
to work most of the time, its not fool proof as can be seen in this case
study:
http://lists.freeradius.org/mailman/htdig/freeradius-users/2006-June/054073.html
   
My question is why cant you rely on only the sql method? And what is the
correct method to clean stale session when using the sql session handling?