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

Alexandru Petrescu <alexandru.petrescu@gmail.com> Tue, 21 July 2015 14:09 UTC

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From: Alexandru Petrescu <alexandru.petrescu@gmail.com>
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Date: Tue, 21 Jul 2015 16:08:48 +0200
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Subject: Re: [v6ops] new draft: draft-yc-v6ops-solicited-ra-unicast
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Le 17/07/2015 18:57, Andrew Yourtchenko a Γ©crit :
>
> 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

and:

- fast handovers: on some links the more frequent the multicast RAs the
faster the handovers are, i.e. less packet loss for end nodes, less
glitches in the video conference stream.

Alex

>
> 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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