[ppml] [address-policy-wg] 2005-01 - Last Call for Comments(HD-ratio Proposal)

Davis, Terry L terry.l.davis at boeing.com
Thu Feb 23 11:51:34 EST 2006


Just as an aside, efficiency targets probably won't work when applied to
mobile networks.  Most large global mobile (ships & planes) platforms
won't use but a much smaller fraction of the assignment.  /24 is the
smallest workable unit for global movement with any currently defined

Localized mobility (trains/ferries/trucking) within a small geographical
area (or even possibly even a region) may be able to get higher
efficiencies depending on strategy/architecture.

Take care

-----Original Message-----
From: Geoff Huston [mailto:gih at apnic.net] 
Sent: Wednesday, February 22, 2006 7:44 PM
To: Randy Bush
Cc: ppml at arin.net; address-policy-wg at ripe.net; sig-policy at apnic.net
Subject: Re: [ppml] [address-policy-wg] 2005-01 - Last Call for
Comments(HD-ratio Proposal)

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
on this topic today.

An HD Ratio of 0.98 imposes a higher  efficiency target than the
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
numbered devices you would qualify for a /19 allocation under an 80%
while under an HD Ratio of 0.98 the end use population is between 3,468
6,841, corresponding to a required address efficiency level of 84% on
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
80% on  the smaller address blocks (/16 through to /24) - this can be 
easily modelled on any spreadsheet of course.



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