[ppml] [address-policy-wg] 2005-01 - Last Call for Comments (HD-ratio Proposal)
gih at apnic.net
Wed Feb 22 22:43:47 EST 2006
At 02:07 PM 23/02/2006, Randy Bush wrote:
> > HD Ratio Ratio Mean Std Dev
> > 0.98 1.04868 0.02285
> > 0.97 1.25899 0.03363
> > 0.96 1.45854 0.03371
> > 0.95 1.63073 0.02848
> > 0.94 1.78332 0.01859
>and what does .98 do to the flight ceiling of small folk?
I'll respond to this question, but in the interests of not wishing to
overwhelming a whole swag of mailing lists I'll make this my last posting
on this topic today.
An HD Ratio of 0.98 imposes a higher efficiency target than the existing
80% rate for all prefix sizes smaller than a /16, and lower than 80% for
allocations greater than a /16 (e.g. an HD Ratio of 0.98 implies an
efficiency threshold of 72% for a /9 allocation.)
As an example, if you had an end use population of between 3,277 and 6,554
numbered devices you would qualify for a /19 allocation under an 80% rule,
while under an HD Ratio of 0.98 the end use population is between 3,468 and
6,841, corresponding to a required address efficiency level of 84% on this
address block in order to qualify for a further address allocation.
The use of an HD Ratio of 0.96 corresponds to an 80% efficiency level for a
/24, so that 0.96 is no worse than 80% for all allocations, whereas
HD Ratios greater than 0.96 impose an efficiency constraint greater than
80% on the smaller address blocks (/16 through to /24) - this can be
easily modelled on any spreadsheet of course.
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