Re: [Roll] Border router failure detection

Michael Richardson <mcr+ietf@sandelman.ca> Thu, 17 March 2022 16:55 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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Comments: In-reply-to Konrad Iwanicki <iwanicki@mimuw.edu.pl> message dated "Thu, 17 Mar 2022 14:35:01 +0100."
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Date: Thu, 17 Mar 2022 11:32:40 -0400
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Subject: Re: [Roll] Border router failure detection
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Konrad Iwanicki <iwanicki@mimuw.edu.pl> wrote:
    > Since the RNFD draft has been adopted by the group, I am expected to
    > propose a set of work items on which we could iterate to progress on
    > the draft.

Please note that it is an anti-pattern (a pathology) of the IETF that we
think that we have to improve/change the document after adoption.
It might be that there is little work to do, but we won't really know until
more people have read it.

    > More specifically, achieving consensus in RNFD is done in such a way
    > that the root node need not be involved. As long as the network remains
    > connected, the nodes are able to conclude that the root has crashed,
    > irrespective of how degenerated the DODAG may be because of the
    > crash. What Pascal suggested (or at least what I understood) is that
    > involving the root and using perhaps a different consensus algorithm
    > may be worth considering.

The idea being, I think, if the root hasn't crashed, it ought to be able to
quickly prove that to all parties involved.

The hidden node problem means that that some nodes might think that the root has
gone, when it is just not very reachable to that node.

A node that can speak to many other rank=2 ("root-children"?) nodes, but
can't see the root ought to just become a child of those other nodes.

    > (Also, I believe that discussing the work items should first be done
    > asynchronously/offline. However, if you prefer allocating a slot at
    > IETF 113, please do let me know.)

Discussion on the ML is always good and appropriate.

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