Subject: another view of fc00::/7

From: Zefram <[email-masked]>
Date: Fri, 6 Jun 2003 19:24:38 +0100

We seem to have a situation of "globally-scoped, persistent, routable:
pick any two".  2000::/3 is globally-scoped and routable.  fec0::/10
is persistent and routable (within its scope).  To allow people the
freedom to "pick any two", we need a way to generate addresses that are
globally-scoped and persistent, without necessarily being (globally)
routable.  That's what fc00::/7 would achieve.

I note that in the architectural traditions of the Internet we're not
very good at handling addresses that are not both globally-scoped and
routable.  That's why we're having kittens trying to work out how to
deal with fec0::/10 and fc00::/7 addresses.

-zefram
-- 
Andrew Main (Zefram) <[email-masked]>
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From: Robert Elz <[email-masked]>
Date: Sat, 07 Jun 2003 02:11:22 +0700

Date:        Fri, 6 Jun 2003 19:24:38 +0100
    From:        Zefram <[email-masked]>
    Message-ID:  <[email-masked]>

  | we need a way to generate addresses that are
  | globally-scoped and persistent, without necessarily being (globally)
  | routable.  That's what fc00::/7 would achieve.

No, you mean that's what you'd like to put in that prefix.   The number,
by itself, can't achieve anything.   What we're lacking is any way to make
a globally-scoped non-routable address.   That is, what gives us global
scoping in 2000::/3 (and most other unallocated spaces, one presumes) is
the routability - the two go hand in hand.   The routing tables define
the one unique user of a globally scoped address.

Take away the routing tables, and there's no longer any universal
motivation to maintain uniqueness, and that is what defines the
scope of the addresses - they end up being locally scoped within
whatever (vague) domain they happen to be unique within.

kre

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From: Zefram <[email-masked]>
Date: Fri, 6 Jun 2003 20:46:12 +0100

Robert Elz wrote:
>                                     What we're lacking is any way to make
>the routability - the two go hand in hand.

Here we're talking about two different things due to the two meanings of
"scope".  You're using the definition where scope = domain of routability.
I should perhaps have clarified, I was using the meaning scope = domain
of meaningfulness.  Let's not rehash the debate about whether these are
really distinct in {theory,practice}.

-zefram