nanog mailing list archives

Re: 95th Percentile != Lame


From: David Klindt <dklindt () cobra ordata com>
Date: Sun, 3 Jun 2001 20:41:03 -0700 (PDT)


On Sun, 3 Jun 2001, Richard A. Steenbergen wrote:

On Sun, Jun 03, 2001 at 07:42:13PM -0700, David Klindt wrote:

I still fail to see how "peak bits" or "bursted bits" are more
expensive than "regular bits".  A 100Mbit FE port costs whatever it
costs, and does not fluctuate with usage.  This is true of almost all
of your links within the network - excluding those where you have
negotiated usage-based billing.  An OC3, point to point, costs as much
as it costs irrelevant of its usage.  Therefore, every bit that
crosses this circuit has a cost.

Why not simply pass this cost on to the customer bit for bit?

It is NOT that the each bit has the same cost - it is the cost of
maintaining enough EXTRA bandwidth so that the downstreams do not
bounce up against the ceiling. That amount is basically covered by
using the 95 rule.

But peak vs non-peak has little to do with 95th percentile. 

Sure they do. I sell bandwidth. I either place a limit on each port, or I
let a client go full open - their call. I MUST be in a position to cover
those costs and yes, at times unused bandwidth. That cost must be past on
to the client if I am to remain in business.  If all clients were willing
to set a ceiling and be forced to live within that ceiling, then no
problem. Clients who select a ceiling pay for the (100 percent) of that
bandwidth (ceiling).

If I do not have the bandwidth to cover the peaks of all clients at the
same time, I am shorting the clients.


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