Subject: RE: Limiting the Use of Site-Local

From: "Michel Py" <[email-masked]>
Date: Mon, 28 Oct 2002 14:46:05 -0800

Margaret,

> What would a light switch do differently to support
> site-local as opposed to global?  It still needs to
> get a prefix from a router and combine it with an IID
> using address autoconf.  So, I don't understand what
> system requirements could be eliminated by refusing
> to support global prefixes.

There is a matter of _implementing_ system requirements, not eliminating
them.

Let's talk about an airplane's IPv6 internal systems. There will be a
requirement that the rudder's embedded controller reacts to site-local
only, just in case a bozo mixes up something. OTOH, the NAV computer
does need to talk to the outside word to extract weather or other
in-flight dynamic data and to report to ground.

All that stuff is displayed simultaneously on the glass cockpit CRTs, so
at some point there is one computer in the plane that has access
simultaneously to external data and to internal data.

Now, explain me how you design that network (the plane) with deprecating
site-locals when global addresses are present. Modern plane designs are
multiple redundant networks that carry data for almost all of the
plane's devices.

Michel.

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From: Margaret Wasserman <[email-masked]>
Date: Mon, 28 Oct 2002 17:53:08 -0500

Are these planes currently implemented using IPv4 RFC 1918
addresses?

And, just for the record, I have not advocated automatically
deprecating site-locals when global addresses are present.
I have advocated administratively constraining site-local
unicast addressing to non-globally-connected networks.

Margaret

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From: Keith Moore <[email-masked]>
Date: Mon, 28 Oct 2002 19:40:03 -0500

> in-flight dynamic data and to report to ground.

that's what packet filtering is for.  

nobody is saying that there's no need for filtering between networks.
what we're saying is that having a single fixed partition of address space
for this purpose is a really, really shortsighted and inflexible way of 
providing that - and one that drastically complicates applications.
and given that far better solutions already exist, one that is totally
unnecessary.

Keith