[ppml] IPv6>>32

[Michael.Dillon at radianz.com]

> The only comment I have
> received on my draft so far is that we probably need to add /44 for very
> large organizations. 

Very large organizations are not very static places. They split off
bits of themselves into other organizations and aggregate other
organizations into themselves on a regular basis.

I don't think there is any case for allowing for more than a
/48 to large organizations. Most large organizations are more
likely to approach providers for several /48's with each
/48 used to service some subset of the whole organization.
I just can't see a scenario in which all traffic in a large
organization will want to use a single gateway.

However, I'm not opposed to defining a second smaller
subnet size at the /56 boundary. Then ISPs can give 
organizations a choice between SMALL or LARGE end-site
allocations. Residential customer and Vehicle Area Networks
would fall into the SMALL category. The LARGE category
would include organizations who operate many VANs or
multiple sites. Then, when a VAN leaves the mother ship
and needs to connect to a wireless hotspot, the ISP 
is already geared up to support /56 end-sites.

However, if we do allow for /56 subsets we need to have
some clear guidance where they should be used, and where
they should not be used, otherwise people who are making
subnet plans for a /48 end-site will incorrectly use the
/56 boundary inside their networks where they should use
smaller blocks. Consider a warehouse with 40 loading docks
and a fleet of 100 trucks based there. The trucks should each
get a /56 but the warehouse itself really only needs a
/64 or maybe a /62.

Any alternatives to /48 need to be clearly explained with
many examples.

--Michael Dillon