How do you (not how do I) calculate 95th percentile?

Jo Rhett jrhett at
Wed Feb 22 18:12:39 UTC 2006

I am wondering what other people are doing for 95th percentile calculations
these days.  Not how you gather the data, but how often you check the
counter? Do you use averages or maximums over time periods to create the 
buckets used for the 95th percentile calculation?

A lot of smaller folks check the counter every 5 min and use that same
value for the 95th percentile.  Most of us larger folks need to check more 
often to prevent 32bit counters from rolling over too often.  Are you larger
folks averaging the retrieved values over a larger period?  Using the
maximum within a larger period?  Or just using your saved values?

This is curiosity only.  A few years ago we compared the same data and the
answers varied wildly.  It would appear from my latest check that it is
becoming more standardized on 5-minute averages, so I'm asking here on Nanog 
as a reality check.

Note: I have AboveNet, Savvis, Verio, etc calculations.  I'm wondering
if there are any other odd combinations out there.

Reply to me offlist.  If there is interest I'll summarize the results
without identifying the source.

Jo Rhett
senior geek
SVcolo : Silicon Valley Colocation

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