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

Andrew Yourtchenko <ayourtch@gmail.com> Fri, 17 July 2015 16:57 UTC

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From: Andrew Yourtchenko <ayourtch@gmail.com>
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Date: Fri, 17 Jul 2015 18:57:32 +0200
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To: "Fred Baker (fred)" <fred@cisco.com>
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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 17 Jul 2015, at 09:34, Fred Baker (fred) <fred@cisco.com>; wrote:

>> 
>> So the next logical thing to do would be to have the router default to
>> unicast Router Advertisements, measure the rate of received Router
>> Solicitations, and switch to multicast RA mode past a certain
>> threshold to cover this sort of situation. Once the number of RSes
>> falls, it switches back to unicast RA mode.
>> 
>> That would get rid of the configuration knob proposed in this ID, and
>> is behaviour that I think could be universal for all link types,
>> rather than just for the case of wireless ones with mobile devices.
> 
> If it were me implementing it, I think I would go about this in a little different way, hopefully simpler. I would want to send at most one (e.g., either zero or one) RA per some interval (a second?). In the normal case, that is sent unicast. However, having sent a unicast RA at time t, if I now receive another RS before t+1, I send the next one (at time t+1) as a multicast.

values of T less than 3 seconds would make performance worse than today.

There are many things to optimize for:

- wireless airtime
- bandwidth used by RAs
- CPU usage sending unicast RAs by router
- energy consumption on devices for more than one medium

Some of them are orthogonal, some of them contradict each other, some of them align. People may want to optimize differently.

I'd opt for simplicity - and use the text Erik Kline posted in another email.

This would allow the developers to adapt for individual use cases on the spot.

--a

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