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 <jrhett@svcolo.com> 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 Note that this isn't my regular email account - It's still experimental so far. And Google probably logs and indexes everything you send it.