95th Percentile again (was RE: C&W Peering Problem?)

From: Richard A. Steenbergen (no email)
Date: Sat Jun 02 2001 - 18:49:32 EDT

On Sat, Jun 02, 2001 at 05:19:16PM -0500, Albert Meyer wrote:
> I almost got caught by this one a few months ago. I was fixing to sign
> a contract with Exodus for a 100bT circuit when I noticed some
> funny-looking language and asked some probing questions, and then
> realized that I had to double their quoted rates before comparing them
> to everyone else. This moved them from the front of the pack back to
> UU-land.
> UUNet is another story. They not only charge significantly more than
> everyone else, but they calculate 95th percentile on the higher of
> incoming and outgoing rather than the average. When I asked my
> salesperson why she couldn't give me a competitive rate, she said
> "Because we're UUNet." She seemed pretty taken aback when I explained

Exodus is the worst on billing bit for bit. The way I read the Exodus 95th
percentile document (though I still havn't gotten it confirmed by a person
who actually knew what they were talking about), they bill for the
MAXIMIUM 95th percentile, on both inbound AND outbound.

UUNet bills for the MAXIMIUM 95th percentile on inbound OR outbound,
whichever is higher, as does AboveNet, and probably the majority of
networks trying to be like UUNet. But a significant portion of other
networks will bill for the AVERAGE under the 95th percentile.

I think the MAXIMIUM is unclear to a lot of people, especially the sales
people if you try to get a straight answer out of them. When most people
refer to the UUNet "95th percentile", this is what they mean. You take
traffic samples, line them up in order, lop off the top 5%, and whatever
the number is for the sample right under that is what gets multiplied by
the cost per mbit. This means that if you push 1Mbps for 25 days and
10Mbps for 5 days you will pay 10 * $$$ per mbit. Average means you will
pay 2.5 * $$$ per mbit (((1 * 25) + (10 * 5)) / 30), obviously a major

A LOT of sales people are misleading or utterly clueless about this, and a
lot of providers actually WILL bill you for the AVERAGE under the 95th
percentile (though if you think about it the 95th percentile makes little
sense if you average it, it was designed to extract the maximium amount
of money while not making people utterly afraid to burst higher).

Moral of the story, check for those words "AND" vs "OR", and "MAXIMIUM" vs
"AVERAGE", ask for their boss and check it again, and then get it in
writing. :P

Richard A Steenbergen <>       http://www.e-gerbil.net/ras
PGP Key ID: 0x138EA177  (67 29 D7 BC E8 18 3E DA  B2 46 B3 D8 14 36 FE B6)

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