[j-nsp] Accuracy of interface stats

[Shane Short]

On 27/09/2009, at 4:18 PM, Richard A Steenbergen wrote:

> 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)

  Hi Richard,

The OP said he was getting the 9.2Gbps measurement from MRTG, which  
would've been a 5min average, hence my comment. Your explaination  
sounds much more plausible though :)

-Shane