[mrtg] Re: 32 versus 64 bit counters

[tony bourke]

Hi Charles,

It's a very good question :)  It doesn't matter what the possible speed of 
your link is, but rather the maximum speed you believe that link will 
push. 

If you've got a Gigabit link, but know there is little or no chance of
pushing beyond 115 Megabits per second (the maximum limit for 32-bit
counters every 5-minutes), over that or any other speed link, then 32-bit
regular counters and configurations will work fine.

However if you believe you will likely push beyond 115 Mbps, then you'll 
need to either a: poll every 1 minute (for a maximum of 575 Mbps), or use 
64-bit counters (for a maximum of somewhere in the Petabits per second, 
the entire library of congress trasnmitted over 6,000 times in 1 second).  

Unfortunately, not many devices have 64 bit counters.

Another potential solution is that some vendors provide "hi" and "low" 32 
bit counters.  If you believe this is the case with your device, let me 
know, I have something to help with that.

Tony




On Mon, 16 Sep 2002, Charles Milhans wrote:

> I am sorry for this newby type of question.
> 
> How do you determine what the polling interval should be when using 32bit
> and/or 64 bit counters and monitoring speeds of 2 Gbps?  I am trying to
> monitor fibre channel switches that use both 1 Gbps and 2 Gbps speeds.  I
> understand that the counters go from 0 to max value and then go back to 0.
> 
> Thanks,
> 
> Charlie Milhans
> 
> -----Original Message-----
> From: tony bourke [mailto:tony at vegan.net]
> Sent: Sunday, September 15, 2002 9:37 PM
> To: Charles Milhans
> Cc: 'mrtg at list.ee.ethz.ch'
> Subject: Re: [mrtg] 32 versus 64 bit counters
> 
> 
> Hi Charles,
> 
> Alex is right, 32 bit counters are much more reliable.  You should
> probably only use a 64 bit counter if you have need to measure bandwidth
> greater than 115 Mbps (assuming a 5-minute polling interval), since 32-bit 
> counters can't handle more than that accurately.
> 
> Tony
> 
> 
> On 
> Fri, 13 Sep 2002, Charles Milhans wrote:
> 
> > Is there much difference in capturing performance data with MRTG using 32
> > bit compared to 64 bit counters?  I found two different MIB definitions
> for
> > performance data on the same port but one definition is specified in 32
> bit
> > counters and the other is in 64 bit counters.
> > 
> > 
> > 
> > 
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-- 
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Tony Bourke				tony at vegan.net


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