This doesn't resolve the problem of ambiguous subnet prefixes
when routing domains merge. So it doesn't go far enough IMHO.

   Brian

Andrew White wrote:
> 
> Let's ask a different question.  Would the following be acceptable:
> 
> -----
> The address space FEC0::/10 is reserved for non-global use.  It is intended
> not to be globally routeable.  All routers MUST by default blackhole any
> packet destined to FEC0::/10, and MAY return a 'destination unreachable'
> message.
> 
> 'Sites' using FEC0::/10 addresses MUST implement a filter at the 'site
> border' that discards source or destination addresses in the FEC0::/10
> space.  Routing protocols MUST NOT exchange reachability information
> concerning FEC0::/10 across the border.
> 
> Any router or node not explicitly configured to do otherwise MAY discard
> (silently or otherwise) any packet with a source or destination address in
> FEC0::/10 space.
> 
> Applications MAY choose to treat FEC0::/10 addresses differently to other
> addresses, and MAY prefer or disprefer them.  Applications MAY assume that
> FEC0::/10 addresses will be filtered before reaching the global internet.
> 
> -----
> 
> This seems to cover the minimum requirements of the relevant parties.  The
> only global requirement is that all routers by default black-hole
> FEC0::/10.  If you choose to use site local addresses, then you come under
> the border router requirements given in the second paragraph.
> 
> The only bugbear I can see is source address selection.  One easy solution
> is to 'prefer closest match' to whatever destination address the application
> selected, which will mean SL matches SL and link-local matches link local.
> Ensuring non-SL matches non-SL may be slightly trickier, depending on
> prefixes, though the current policy of allocating from 0000::/12 will prefer
> global-global.
> 
> And maybe something should be added to say "If you stick these things in a
> globally accessible DNS, don't be surprised when connections to your hosts
> fail."  And maybe a policy to NXDOMAIN reverse lookups for
> [C-F].E.F.in6.arpa.
> 
> In short, there is almost no extra effort for those who don't implement SL
> addresses - all the work is pushed to those who do.
> 
> Notice that the above text says nothing about how FEC0::/10 addresses are to
> be allocated.  All it does is reserve the space as 'not globally routeable'
> and put policies in place to stop this information getting where it
> shouldn't.
> 
> --
> Andrew White                [EMAIL PROTECTED]
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