Re: [homenet] Let's make in-home ULA presence a MUST !?

Ted Lemon <mellon@fugue.com> Tue, 14 October 2014 13:44 UTC

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From: Ted Lemon <mellon@fugue.com>
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Date: Tue, 14 Oct 2014 08:44:03 -0500
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To: Erik Kline <ek@google.com>
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Cc: HOMENET Working Group <homenet@ietf.org>, Pierre Pfister <pierre.pfister@darou.fr>
Subject: Re: [homenet] Let's make in-home ULA presence a MUST !?
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On Oct 14, 2014, at 3:12 AM, Erik Kline <ek@google.com> wrote:
> Among other things, if my home edge router losing it's upstream it (in
> theory) doesn't have to deprecate the global prefix in the home, just
> the default route.  Since I can't get to the Internet anyway, all I
> need is (almost) any prefix, and the one I have is as good as a ULA
> (if not better, since the upstream loss may just be a flap).

This is something we discussed at length back when we were doing the architecture document.   The problem with this approach is that it exposes you to flash renumbering when you get back online, or if you can't do flash renumbering, you could easily find yourself without connectivity because you are using the wrong source address.   Deprecating the global address when upstream connectivity goes away, and preferring the ULA for local communication, addresses this problem.   So I think that we need to have a really clear argument _against_ using ULAs to solve this problem in order for what you are saying to be true, and I don't remember that being an outcome of the previous discussion.

So while I am not sure I agree with Pierre's conclusion, I think his reasoning is pretty sound.