[rrd-developers] Re: Counter limitation

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Mon Oct 25 11:45:53 MEST 1999

> I have adopted a RRD tool with mrtg.
> But, i notice that i can't see actual utilization
> when the utilization of link is over about 120Mbps.
> We use the Cisco router with high bandwidth link,
> 155Mbps ATM, FastEtherChannel, etc.
> In my opinion, the problems are our router which uses
> the 32bit counter.
> Therefore, i have modified some code of mrtg and
> decreases the interval to 1 minute.
> It' looks fine. However, this is not the solutions because of
> 32bit counter.
Actually it can be.  RRDtool does not suffer from counter wraps (as opposed
to MRTG) provided the counter only wraps once.  This means that in your
case the maximum increase can be 2^32-1 octets per minute and therefore
the maximum rate can be 572,662,306 bps ( (2^32-1)*8/60 )

If you write your own front end, it may be wise to use 64-bit counters
whenever possible.

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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