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Re: SUMMARY - 95th percentile calculation

  • From: Bill Stewart
  • Date: Tue Feb 28 05:10:59 2006
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I'm not operationally involved at AT&T, but what I've been told is that we track
5-minute samples in both directions, and do the 95th% calculation on
all the samples,
as opposed to tracking 95% of inbound-only or outbound-only or
max(in,out) samples.

On 2/27/06, Jo Rhett <[email protected]> wrote:
> My thesis that I wanted to prove or disprove was that the market seems to
> have standardized how they calculate 95th percentile.  Years ago if you
> asked all your uplinks you'd get wildly different answers.  Averages or max
> values over days, weeks or months.  Rarely would two answers jive.
> But it appeared that most providers are now using 5 minute averages as the
> value input over a billing month for 95th% calculation.  Was this truly
> standard now?
> The answer is yes.  All of our paid transit links use 5 minute averages,
> and all but one of the replies to my query here did too.
> 8 providers use 5 minute averages of 30 second counter checks as the base
> value calculated over the billing month.
> 2 providers use 5 minute averages of 1 minute counter checks as the base
> value calculated over the billing month.
> 8 providers use 5 minute implicit averages (a single counter check) as the
> base value calculated over the billing month.*
> 1 provider uses the maximum value found in 5 minutes of 1 minute counter
> checks for the 5 minute value, and calculates that over the billing month.
> 1 provider uses 5 minute implicit averages (a single counter check) but
> calculates that over a fixed 30 day month. (I didn't ask what they did with
> the extra days)
> At first glance my tendancy would be to say that 20 answers is hardly
> authoritative, but the 30 second counters (first listed) comprise 6 of the
> top US bit movers, and 2 of the largest bit pushers so I'm satisfied with
> the results for my purposes.
> * One very large bit mover that I know uses 32 bit counters claimed to only
> be checking every 5 minutes.  We're pushing enough to them to rotate that
> counter in that interval, so I actually disbelieve this answer but I'm
> reporting it as they said it.
> --
> Jo Rhett
> senior geek
> SVcolo : Silicon Valley Colocation

             Thanks;     Bill

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