[address-policy-wg] Re: [ipv6-wg] closed network and need for globa l uniqe IP space

At 09:38 PM 25/11/2005, Gert Doering wrote:
>Hi,
>
>On Fri, Nov 25, 2005 at 11:25:07AM +0100, Roger Jorgensen wrote:
> > > On Fri, Nov 25, 2005 at 10:12:35AM +0100, Roger Jorgensen wrote:
> > > > The solutions aren't really that tricky but let me mention a few
> > > > options...
> > > > * Site local would have solved our problem BUT it's obsolite, quite
> > > > stupid really.
> > >
> > > That's why there are ULA ("unique local addresses") now.  They should
> > > fit your needs pretty well - as much addresses as you want, and the
> > > guarantee to be not officially assigned to anyone.
> >
> > what about the other part about globaly unique when we connect to other
> > network of the same type?
>
>The idea is that ULAs are random-generated in a way that makes it "fairly
>unlikely" that you end up in an address collision.  But there is no
>guarantee, of course.
>
>There is also a second sort of ULAs that are globally unique but still
>private, but as far as I know, there is no registry yet that will hand
>them out.  So these can't be used yet.


This is an area that has not gone completely dormant. The "unlikeliness"
that Gert refers to is the classic birthday problem, and the probability that
2 parties have chosen the same number rises above 0.5 once the candidate
population exceeds 1.24 million.

So some form of central or coordinated registry action is necessary to ensure
that there are no collisions in these numbers. At APNIC we've been looking
at how such a system could be supported.

  Geoff