[rrd-users] DERIVE vs COUNTER

Alex van den Bogaerdt alex at ergens.op.het.net
Fri Mar 21 17:25:43 CET 2008

On Sat, Mar 22, 2008 at 02:46:26AM +1100, Jean-Yves Avenard wrote:

> >  This should be detectable. A suggestion follows below.
> actually, the uptime value of the modem doesn't reset when there's
> loss of DSL sync, so I can not easily test the way you are suggesting.

Perhaps there's another flag to use, dunno.

> >  And, perhaps more important, the rate computed cannot be more than
> >  12mbps.  Use this knowledge, that's why rrdtool know about a minimum
> >  and maximum rate.
> Ok, I understood that the maximum value entered was the maximum value
> of the counter: so here 2^32.
> So if I entered as maximum value 12mbit/s (so around 90000000: 1.5MB/s
> * 60) it should detect the reset easily...

min and max are rates.  90000000 means 90000000 bytes per second.

> Another case this is happening is on my FreeBSD router.
> To measure some specific traffic, I created a MIB for snmp-net
> allowing to read some firewall (ipfw) rules.
> each time I edit the firewall rule (which can just be counters), it
> resets all the counters.

Then hook rrdtool in there. Or live with the occasional "false positive"
when a true counter overflow is ignored as if it were a reset.

Alex van den Bogaerdt

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