Keith Moore wrote:
>
> For the sake of completeness:
>
> Another idea I heard last week (sorry, I forget who suggested it)
> is to use the number of seconds since some epoch (say 2002.01.01 0000 UTC)
> when the network was established, as the probably-unique prefix.
>
> Though I do wonder whether we might see multiple networks automatically
> "turned on" at the same "round number" time, causing collisions.
Well, it's a one-off function ("get me a prefix now!") that never needs
to be repeated, and doing it automatically at a set time would indeed be
a MUST NOT. But apart from that I like the idea - if we did it in a 38 bit
field under FEC0::/10 it takes a few thousand years to wrap, it doesn't
need a seed like a random number generator, and it's free.
Brian
>
> Keith
>
> > As a method of doing globally unique site local addressing:
> >
> > Assuming aggregability is not an issue within a 'site' sized network,
> > consider generating site local subnet identifiers at the router, based on
> > IEEE EUI-48 identifiers (such as MAC addresses).
> >
> > For example, generate as fec0::/12:
> >
> > 12 bits: fef
> > 48 bits: MAC
> > 4 bits: 0 or subnets
> >
> > or, if we don't want them in fec0::/10
> >
> > 10 bits: fe0
> > 48 bits: MAC
> > 6 bits: 0 or subnets
> >
> > The '0 or subnets' is to allow for the possibility of choosing one EUI-48 on
> > a router and using that to allocate all appropriate subnets.
> >
> > By piggybacking on the existing registration scheme, we generate "unique"
> > site-local subnet ids at the router without needing external registration or
> > administration.
> >
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Brian E Carpenter
Distinguished Engineer, Internet Standards & Technology, IBM
On assignment at the IBM Zurich Laboratory, Switzerland
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