acct-delay-time appears to be off

[Steven Staples]

I have been looking at this, and scratching my head.

It appears as if the (timestamp -(minus) acct-delay-time) does not always =
the actual start time of the session.   From my observation, and log reading
script, I have found that there could be a +/- 1 second variance in either
the timestamp, or the acct-delay-times.  

Could this be the router sending it's time, and the radius box intercepting
it at a possible rounding up or down to the next second?

Is there a way to use the microseconds to ensure that these values are
accurate all the time?

Basically, what I am trying to achieve, is that when I insert into my
'MySQL' database that it's updating the proper start record on
'Interim-Update' or 'Stop' records, and not creating a new start record for
it when it's just off by 1 second or so.

Is there possibly a better way to create a unique key, rather than what I am
currently using as a unique group of fields:  
Framed-ip-address + nas-ip-address + user-name + acct-session-id +
((timestamp - acct-delay-time) - acct-session-time)

Steven Staples