[arin-ppml] Opposed to 2010-9 and 2010-12

michael.dillon at bt.com michael.dillon at bt.com
Fri Oct 15 05:19:23 EDT 2010

> Aren't ARIN's own guidelines:
> "/56 for small sites, those expected to need only a few subnets over
> the next 5 years."

Actually, no they are not. ARIN's guidelines are:

    "The following guidelines may be useful (but they are only 

Followed by some additional text including that statement. But ARIN policy
is not and engineering manual. The IPv6 addressing architecture from
IETF is a /48 for all end sites unless there is some reason why an end
site cannot ever grow beyond a single LAN segment.

The ARIN policy text was reworked to include mention of /56 because the
cable TV industry had a need to allocate smaller than a /48 and wanted
that to be formally recognized in policy. They have to address every
home that the cable passes and many of those homes will never ever be
connected to that cable. This blows out their HD ratio from day 1 and 
ensures that they can never get another ARIN allocation, unless ARIN
changed the policy to allow for /56 endsites. Which we did do.

That however was a policy decision, not an engineering one. The /48 per
end site rule of thumb still stands.

> But I suppose you will explain to me why that text doesn't say what I
> think it says.

Because you are not a real lawyer. Real lawyers understand that context
is important and do not try to interpret words outside of context.

--Michael Dillon

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