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Re: CPEs

On Mon, Jan 07, 2008 at 09:26:26AM +0100, Leo Vegoda wrote:
> On 4 Jan 2008, at 16:32, Shane Kerr wrote:
> 
> [...]
> 
> >>11. Do we expect ISPs to provide reachability for a new and old
> >>prefix concurrently when changing prefixes or do ISPs provide
> >>long-time stable prefixes to IPv6 customers? If "no" on both, then
> >>how do we avoid disconnected sessions on prefix changes?
> >
> >Personally I like the model of providing reachability for both old
> >and new during renumbering. But... since an ISP only gets a few
> >thousand /48 at a time, they may be faced with resource scarcity,
> >and not have the space (GROAN!!!!).
> 
> On the whole, ISPs assign addresses for the period during which you
> pay them for a service. I doubt there will be any resource scarcity
> leading to revoked assignments while end-sites continue to pay for
> service from their ISPs. I don't think an alternative where random /
> 48s move around between different ASs is a good model to promote.

Well, the scenerio I'm thinking of does not involve a new AS. For
example, if your ISP opens a new site closer to your home, they may
want to route your connectivity into the new site, which could very
well involve renumbering.

So, Ilijtsch's question is important.

I am told that today the best way to do such a migration in IPv4 is
for ISPs to pick a time to move customers to the new numbers, and use
ever-decreasing DHCP lease times to insure that users renumber as
close to that time as possible - but not to overlap the address spaces
for any time.

IPv6 was designed to be able to allow end hosts to more-or-less
painlessly migrate between addresses. I don't know if this has been
widely tested (I suspect not). Plus, unless there is some clever work
on both the ISP and customer side, a renumbering can affect the end
site.

Again, my preference is to support both old and new addresses during a
renumbering, but I don't know if IPv6 is mature enough technology, or
if we have enough space after squandering so much of it.

--
Shane