Re: [Roll] some comments on draft-thubert-dao-projection-00.txt

Michael Richardson <mcr+ietf@sandelman.ca> Mon, 06 July 2015 14:40 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: Mon, 06 Jul 2015 10:40:45 -0400
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Subject: Re: [Roll] some comments on draft-thubert-dao-projection-00.txt
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Pascal Thubert (pthubert) <pthubert@cisco.com> wrote:
    > The draft indicates that the root knows some topological information
    > from the non-storing DAO (it knows all about the DODAG).

yes...

    > Per RFC 6550, a path constructed by storing-mode DAO messages is
    > directional, packets flow parent to child, and we do not want to
    > introduce confusion by changing any of that.  Thus the segment that is
    > constructed from the segment egress to the ingress.

I don't think I understand what this is an alternative to.
I.e. what would the way to do it wrong be?  Why are you suddendly talking
about storing-mode DAO messages.

    > It results that the segment is directional but not that it is
    > necessarily flowing down the DADOG, this depends on how much
    > information is available to the root or whatever PCE is used as a
    > helper.

This seems to imply that traffic could flow across the mesh... i.e. hop
From branch to branch.   How would the DODAG root know that this was possible
using pure RPL?  I think that it couldn't without 6top or something.

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