[j-nsp] Accuracy of interface stats

The Drifter prophecy_68 at hotmail.com
Sun Sep 27 04:34:56 EDT 2009

Thanks for the points.


The link uses OC-192 over DWDM. 

How can we confirm that the interface numbers for input/output packets are updated every 10 seconds and not every five minutes?



> Date: Sun, 27 Sep 2009 03:18:16 -0500
> From: ras at e-gerbil.net
> To: shane at short.id.au
> CC: prophecy_68 at hotmail.com; juniper-nsp at puck.nether.net
> Subject: Re: [j-nsp] Accuracy of interface stats
> On Sun, Sep 27, 2009 at 02:52:34PM +0800, Shane Short wrote:
> > You'll find that 9.2Gbps was the 5minute average-- you were probably 
> > bursting well above that frequently, hence the drops.
> > 
> > There was a massive discussion about this on the nanog list, depending 
> > on the type traffic your transiting, you shouldn't run your link at 
> > hotter than 70-90%
> I don't think the show interface counters are 5 minute averages. A
> "monitor interface" updates every 2 seconds and seems to catch major
> changes in traffic in about that much time, so the hardware is clearly
> capable of updating counters within a few seconds (definitely well under 
> 10s). I don't spend much time looking at show interface counters, but a 
> quick poke shows them updating what appears to be every 2-3 secs, so it 
> seems likely that these would be similarly real-time to the monitor 
> interface rate.
> To the OP: This doesn't happen to be a OC-192 doing WAN PHY 10GE does
> it? Those will definitely top out at almost exactly 9.2Gbps, after you
> figure in the overhead for sonet + ethernet + the lower data rate.
> -- 
> Richard A Steenbergen <ras at e-gerbil.net> http://www.e-gerbil.net/ras
> GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)
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