[36793] in North American Network Operators' Group
Re: What does 95th %tile mean?
daemon@ATHENA.MIT.EDU (Toby_Williams@enron.net)
Fri Apr 20 05:22:54 2001
From: Toby_Williams@enron.net
To: nanog@merit.edu
Message-ID: <88256A34.00334E65.00@ecmta1.enron.net>
Date: Fri, 20 Apr 2001 10:19:17 +0100
Mime-Version: 1.0
Content-type: text/plain; charset=us-ascii
Content-Disposition: inline
Errors-To: owner-nanog-outgoing@merit.edu
_95th%ile is not a robust mechanism for billing_
It neither addresses variance nor average use effectively and can be gamed
quite easily. It's some kind of best fit system for billing buyers with "normal
behaviour".
Where in maths class did they ever say that scraping off the highest n percent
of a data set in isolation, gives a good indication of anything? Don't you need
to look at the mean and 90th percentile together to fairly evaulate
distribution.
I think the reason it's so popular currently is that it's easy to describe
(hence sell) and fits normal use reasonably well, so from a "normal buyer's"
perspective is OK. Just as long as everyone is honest.
In a thirty day billing period 95th%ile gives you one and a half days of *free
bandwidth*. 90th%ile gives you three days of *free bandwidth*.
From the seller's perspective, once this starts getting gamed a little more I
can't see it having much of a shelf life, and more sophisticated billing will
surface, similar to the power industry Sean sites.
I'm quite surprised we're not there already.. has anyone started venturing down
this route yet? (other than flat rate)
toby
