[address-policy-wg] RE: gazing into the future

Lorenzo Colitti a écrit :
> On Wed, Dec 2, 2009 at 6:53 AM,  <michael.dillon at bt.com> wrote:
>> of 6RD and the larger allocations that might happen. I get the
>> sense that this would not cause a problem as long as we assume
>> that 6RD will be decommissioned within 5 to 10 years.
> 
> You are assuming that address space will be returned when 6RD is
> decommissioned? That doesn't sound likely to me.

1.
As a matter of fact, it would not even need to be decommissioned in most 
cases:
- If an ISP has only one IPv4 prefix, it doesn't need a more generous 
prefix than /32 for 6rd. There is nothing to be decommissioned.
- If it has several IPv4 prefixes, but also  an installed base of more 
than 64K customers (or a short term plan to have it), then, to assign 
/48s to its customers as currently recommended, it deserves from its RIR 
  a more generous prefix than a /32 anyway (even when 6rd is replaced by 
native IPv6 routing). No need to decommission.

It is only for those that still have several IPv4 prefixes an no short 
term plan to exceed 64K customers that the need to decommission would exist.
This makes it a secondary consideration.
It may IMHO be ignored.

2.
IPv6 introduced TTLs of assigned prefixes so that, combined with DNS 
dynamic updates, renumbering becomes realistic.

Some ISPs, when they get a more generous prefix than before, e.g. going 
from a /32 to a /28, may therefore prefer, after some coexistence delay, 
to route only on the shorter prefix.
They can then be decommissioned without problem.
This simplifies their network, and helps keeping tier-1 routing tables 
short.

Regards,

RD