Re: [Roll] unaware leaves - graceful shutdown of attached-6LR

Michael Richardson <mcr+ietf@sandelman.ca> Wed, 15 April 2020 20:39 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Routing Over Low power and Lossy networks <roll@ietf.org>
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Date: Wed, 15 Apr 2020 16:39:25 -0400
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Subject: Re: [Roll] unaware leaves - graceful shutdown of attached-6LR
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Rahul Jadhav <nyrahul@outlook.com> wrote:
    > In the event that the attached 6LR needs to gracefully shutdown, it
    > needs to inform the RUL(s) to detach and possibly move to another 6LR.
    > I believe this could be done using NA(EARO, Status="Removed"); from the
    > attached-6LR. Can this NA be multicasted if the attached-6LR has more
    > than one RULs attached to it?

Pascal Thubert \(pthubert\) <pthubert=40cisco.com@dmarc.ietf.org> wrote:
    > Normally this is done using a final RA. But the RA is broadcast so
    > unicasting a NA with ‘R’ flag off is a great idea. This is the exact
    > signal that this router does not serve this node. Lifetime 0 would
    > indicate that the router removes the NCE.

The other reason that I think that we need to unicast the NA is because it
needs to occur when the sleepy device is awake.
That could take some time to reach all devices!

I agree that it would be better to do this before the 6LR goes away, as the
next time a device like a window-smash sensor wakes up could be because it
needs to send an ALERT :-)

I think that in a 6tisch scenario, it might take a few cycles of the schedule
to get all the unicast NAs sent.

--
Michael Richardson <mcr+IETF@sandelman.ca>ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-