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

> - Since RIRs allocate /32s and recommend to assign /48s to 
> customers, each ISP having more than 64K customers should get 
> at least a /28. With such a /28, any ISP that has several 
> IPv4 prefixes can deploy 6rd with /60s assigned to all its 
> customers (typically more than 64K).

Wait a minute. If a /28 allocation is enough to assign /60
blocks, then by giving the ISP 4 more subnetting bits, i.e.
a /24 allocation, they should be able to give /56 assignments
to all their customers. That is the way to do this properly.

> - A /60 per customer site is largely enough to start using 
> IPv6, even for sophisticated users that configure several 
> LANs in their sites.

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.

There is no need to make customer assignments smaller 
than /56.

> - For an ISPs that initially gets only as /32 and has several 
> IPv4 prefixes, assigning /64s to its customers is much better 
> than no IPv6 at all (as Free has demonstrated, and because 
> most sites don't support several LANs anyway).  

No, assigning /64s is far worse because their people will not
be properly trained, and when the word gets out, nobody will
want to work there because it will be a black mark on their
CV. It is better to go back to RIPE, explain the situation, 
and get a /24 or /21.

> o ISPs that don't obtain more generous IPv6 prefixes than 
> /32s can at least start with /64s assigned to customers.

This is called compounding your mistakes. Do not do this.

> o RIRs should allocate at least /28s to ISPs that have 
> several IPv4 prefixes and plan to deploy 6rd.

Wrong. RIRs should evaluate the size of allocation needed to
properly deploy 6RD using /56 assignments for customers, and
then allocate a block big enough to handle this deployment.

> o These ISPs should return these prefixes if, for any reason, 
> they become more generous than needed.

That has always been part of the RIR rules.
And that is a major reason why people should be given huge
allocations to deploy 6RD, if they have decided that 6RD
is the best way to go. We do not want ISPs to get locked
into 6RD because of bad architectural decisions, so we
must ensure that they have enough address space to assign
/56 or /48 to all customer sites.

--Michael Dillon