Comparing live sessions between NAS and freeradius

[m3freak at thesandhufamily.ca]

Hi Everyone,

I'm using SQL for Simultaneous Use checking.  It works in that if someone
tries to auth when they're already logged in, they're rejected.  However,
sometimes the acct stop packet never makes it to freeradius (for whatever
reason) when the user logs off.  This leaves the "acctstoptime" field in
the radacct table as NULL, which freeradius interprets as a live session. 
Obviously, the session doesn't actually exist on the NAS.

I've read what checkrad does. From what I understand after reading the
config files, checkrad only works in conjunction with radutmp.  I'm not
using radutmp since I've deployed freeradius with SQL.  So, how do I ensure
what freeradius' understands to be a live session matches what the NAS
sees?  How do I update a user's acctstoptime when the NAS doesn't have a
session for that user, but the DB shows as "NULL" (i.e. freeradius believes
the user is live)?

Is this where the "deletestalesessions" parameter in sql.conf comes in? 
What if users are logged in for days at a time?  Should lease-duration just
be bumped up to something that works better for us than the "3600" default?

Regards,

Ranbir