[address-policy-wg] IPv6 allocations for 6RD

> > That's not the point. A /60 assignment is wrong. If software 
> > developers and equipment vendors get the idea that /60 is 
> normal, then 
> > they will embed that assumption in their products and it 
> will make the 
> > transition from 6RD to native v6 more difficult.
> 
> You keep repeating this but which document or standard says 
> /60 is wrong ?

RFC 3177 says that ISPs should assign a /48 to every site
except in the case of very large subscribers.

Geoff Huston did a paper some time ago that demonstrated a
slim possibility of running out of IPv6 addresses using
/48 everywhere and proposed a couple of small changes, one
to the HD ratio, and dropping to /56 assignments for private
residences. Some RIRs have adopted this into policy, but
regardless of whether or not it is in RIPE policy, the /56
for private residences is still good practice and is being
tracked by vendors.

> > There is no need to make customer assignments smaller than /56.
> 
> 
> But why ? I can imagine /60 is enough for Joe the plumber 
> even if sensor networks would take off...

Because the whole point of giving sites a /48 is to ensure that
they have more than enough so that 99% of them will never ever
have to expand beyond /48. This business of /64, /48 and /32
quasi-classful boundaries is meant to stop the network architecture
reshuffle that IPv4 forced on people whose networks were growing.

There is a competition law aspect to this too. If everyone assigns
their customers a /48 (or a /56 for private residences) then customers
will be able to move to another ISP (competition) without restructuring
their network. It will be a simple prefix change. This is one of the
features of IPv6 to make renumbering easier. If an ISP assigns their
customers /60 blocks then they are at risk that some of those 
customers could sue them under the competition laws because the /60
becomes an artificial barrier to changing ISPs.

There just isn't any technical requirement to assign customers 
less than a /56 prefix. Even if RIPE policy does not yet mention
/56 prefixes, they are still a good practice based on the findings
of Geoff Huston.

--Michael Dillon