[ppml] Re: HD ratio proposal vs. Changing percentage burden

Michael.Dillon at radianz.com Michael.Dillon at radianz.com
Wed Mar 24 09:50:33 EST 2004

>"A slide presentation, a spreadsheet, some PERL scripts and some 
>and "if anything is unclear...I will try my best to answer questions"

Not everybody learns things the same way. Some people
like to see graphs and charts and tables of numbers
and a simple ratio calculation implemented in 
running code rather than abstractly described. 
The background pages are for them.

>HD Ratio trades administrative ease off for fairness.

Nope. The HD Ratio retains administrative ease, just
changes the calculation of the threshold for entering
a new application. And it increases fairness by
recognizing that IP addresses are not like the peas
on your dinner plate. If you leave peas behind on
your plate, you are wasting food, plain and simple.
But if you leave IP addresses unassigned to network
devices you are not necessarily wasting any at all
because the CIDR addressing structure requires that
all subnet requirements be rounded up to be some
integral number of blocks, each of which contains
a power-of-2 addresses. And although sometimes you
can use 3 /26's instead of a /24, this triples the
number of route table entries you consume and therefore
it does not scale. The HD Ratio helps people
scale their networks.

>Not every segment of the industry
>'truly' benefits but everyone would be subject to the increase
>complexity...all this as I understand it.

That is true of last year's HD Ratio proposal
but this year I made a lot of changes based
on comments that I received from many people.
That's why the word "choose" is in clause 1
of the proposal, and I quote:

  1. Anyone who has already been allocated 4096 IPv4 addresses or
  more may choose to have additional requests for IPv4 addresses
  evaluated using an HD (Host Density) Ratio calculation to determine 
  sufficient utilization instead of a fixed percentage threshold.

>Also, could you comment on why HD Ratio would be the preferred approach 
>change? Is the educational burden less to overcome the status quo of
>administrative ease than simply changing the percent utilization burden?

To date I have not seen any other proposal to change the
80% threshold. Now that we are using the HD Ratio for IPv6
allocations, I believe that the preferred approach is to
bring IPv4 into alignment. Eventually we all will be using
the HD Ratio. This policy proposal is a beginning because
it offers the choice to change but does not mandate a
schedule for change. It allows the breathing space necessary
for everybody to learn how HD Ratio works and implement
it at their own speed. 

--Michael Dillon

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