Re: [v6ops] new draft: draft-yc-v6ops-solicited-ra-unicast

Lorenzo Colitti <lorenzo@google.com> Tue, 21 July 2015 09:36 UTC

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From: Lorenzo Colitti <lorenzo@google.com>
Date: Tue, 21 Jul 2015 11:35:49 +0200
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To: Erik Nordmark <nordmark@acm.org>
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Cc: "draft-yc-v6ops-solicited-ra-unicast@tools.ietf.org" <draft-yc-v6ops-solicited-ra-unicast@tools.ietf.org>, v6ops list <v6ops@ietf.org>
Subject: Re: [v6ops] new draft: draft-yc-v6ops-solicited-ra-unicast
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On Mon, Jul 20, 2015 at 8:18 PM, Erik Nordmark <nordmark@acm.org>; wrote:

> But in terms of implementation, isn't it simpler to always(*) respond to a
> RS with a unicast RA?
>

It would be simpler to document, yes, but I don't know that we should make
a one-size-fits all recommendation, because there might be link types or
environments where this is more expensive.

As background, the text in RFC4861 comes from the old concern that all
> devices might boot at the same time when the power is re-established after
> a building power failure; that doesn't happen since most devices (laptops,
> smartphones, IoT devices) have batteries today. In that case it might have
> made sense to sending fewer RA messages by using multicast.
>

This sort of thing can still happen. If lots of devices join at once,
(e.g., if something happens at a large-scale event when hundreds of people
pull their phones out of their pockets and turn them on at the same time),
it may well be cheaper for the network to send one multicast RA.

I'm not opposed to changing the standards as well, but I think respinning
RFC 4861 would require much more careful consideration than simply
publishing an operational guidance document such as this one. Perhaps we
can just recommend in this document that 6man consider this operational
need and consider modifying the protocol?