What does 95th %tile mean?

Thu Apr 19 14:59:50 UTC 2001

Here's how I explain it on our burstable T1's & T3's (We bill at the 90th
percentile BTW):

Burstable T1 Explanation

I hope that this explanation helps:

Consider that your Internet usage is probably similar to 99% of all business
users. You will probably use the circuit Monday through Friday between the
hours of 8am and 5pm. Utilization in the off hours and on weekends should be
close to zero. This means that over an entire month (720 hours), you will
have access to the circuit for only 180 hours.

Remember, in that 180 hours (8am - 5pm), you will not be constantly
uploading and downloading data. It is in fact quite the opposite. Internet
traffic is "bursty". For example: If you are viewing a web page and you hit
your enter key, data is transmitted and the image and text load. Once it is
loaded, the transmission stops and you read the web page. At this point the
bandwidth is again sitting idle and utilization is back at zero. This is the
cycle that repeats itself during the day so it is a safe bet that your
utilization in that 180 hour time frame is 50% at best.

This now leaves you with 90 hours of utilization for the month.
Since we bill you at the 90th percentile, this means that we will discard
the highest 10% of you bandwidth peaks. The 10% equates to 72 hours. This
means that we will subtract the HIGHEST 72 hours of utilization from the
remaining 90 hours.

This now leave you with the lowest 18 hours of utilization for the month.
Again, I can't guarantee it, but it is very unlikely that your lowest 18
hours will be greater than 100k.

This graph illustrates a typical business customers utilization on a  T-1
circuit.
http://www.intermedia.com/images/businessinternet/products/lineutil.gif

Jeff Dearborn
Major Account Manager
Intermedia Communications Business Internet
800.993.4439 x2418 toll free
301.847.2418 direct dial
301.419.0288 fax
http://www.intermedia.com/

		-----Original Message-----
		From:	Alex Rubenstein [mailto:alex at corp.nac.net]
		Sent:	Thursday, April 19, 2001 10:09 AM
		To:	'nanog at merit.edu'
		Subject:	What does 95th %tile mean?

		I've gotten myself into an argument with a provider about
the definition of
		'industry-standard 95th percentile method.'

		To me, this means the following:

		a) take the number of bytes xfered over a 5 minute period,
and determine
		rate for both the inbound and outbound. Store this in your
favorite
		data-store.

		b) at billing time, presumably on the first of the month or
some other
		monthly increment, take all the samples, sort them from
greatest to least,
		hacking off the top 5% of samples. Actually, this is done
twice, once for
		inbound, once for outbound. Then, take the higher of those
two, and multiply
		it by your favorite $ multiple (ie, $500 per megabit per
second, or $1 per
		kilobit per second, etc).

		I think that most people agree with the above; the issue we
are running into
		is one rogue provider who is billing this at in + out, not
the greater of in
		or out.

		How is everyone else doing it? Specifically, larger folks
(UU, Sprint, CW,
		Exodus/FGC, GX, Qwest, L3)

		Thanks!