Re: [Roll] stitching PDAO segments

["Pascal Thubert (pthubert)" <[e-mail]>]

Hello Toshio

6TiSCH provided a generic Architecture in which RPL and qrAW have different role to play.

A 6TiSCH tract is computed by a pce but with RPL the nodes do not care where that logical function is located and simply talk to the root. Either the root hosts a pce or it talks to a pce to get the computation done.

A projected track can be deep in a RPL DODAG.  When deep, a node cannot ask the root to change the path at each hiccup of the radio . This is why a simple serial track can be too limiting and the root may prefer to provide a complex track with redundancy that always works even if some segments fail randomly for split seconds.

RAW if formed would work on optimizing the use of a complex track to limit the waste of energy when the track lots of redundancy. RAW operates at the forwarding level over a track on a short time scale whereas RPL routing decisions are made on statistical time scales orders of magnitude longer.

Do I make sense?

Pascal

Le 24 juil. 2019 à 22:10, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>> a écrit :

Hi Pascal,

I thought 6TiSCH Track forwarding is a completely different forwarding scheme
from RPL/IPv6 forwarding, as implied in https://tools.ietf.org/html/draft-ietf-6tisch-architecture-24#section-3.6

In that case, we don't have to relate DAO projection and Track, I think.
Or, maybe DAO projection is one implementation of Track forwarding, with RPL root playing
the role of PCE?


From: Roll <[e-mail]<mailto:[e-mail]>> On Behalf Of Pascal Thubert (pthubert)
Sent: Thursday, July 25, 2019 7:10 AM
To: Routing Over Low power and Lossy networks <[e-mail]<mailto:[e-mail]>>
Subject: [Roll] stitching PDAO segments

Dear all

Following up on stitching PDAO paths at the meeting today:

As you know, a 6TiSCH Track can be a lot more complex than a sequence of nodes (see https://tools.ietf.org/html/draft-ietf-6tisch-architecture-24#section-4.5.3)
It results that deploying a Track requires stitching segments into a DODAG from source to destination.
What makes the most sense for a 6TISCH Track is probably that each track is defined as a DODAG local instance for the source. All the PDAO segments would be stitched together into that DODAG to form a Track.
The current draft allows for this but a section that explains it all would certainly be useful.

Are we all OK that I propose some text about that?

All the best

Pascal
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