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Re: [Roll] RPL P2P - Clarify that hop-by-hop is identical to RPL Storing mode

Mukul Goyal <mukul@uwm.edu> Wed, 17 November 2010 19:47 UTC

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Date: Wed, 17 Nov 2010 13:48:15 -0600
From: Mukul Goyal <mukul@uwm.edu>
To: Anders Brandt <abr@sdesigns.dk>
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Subject: Re: [Roll] RPL P2P - Clarify that hop-by-hop is identical to RPL Storing mode
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Hi Anders,

[Anders]

The current RPL P2P draft
http://tools.ietf.org/html/draft-dt-roll-p2p-rpl-02

appears to be a little unclear on the terms

* hop-by-hop route
* source route
* RPL Storing mode
* RPL Non-storing mode

The introduction does a nice job of explaining the
difference of the two uncompatible modes but forgets
to point out the detail that the
RPL Non-storing mode is using source routes while
RPL Storing mode implements hop-by-hop routes.

[Mukul]

The introduction section does say that

"In non-storing mode operation, only the DAG root maintains downward routing
   information and hence a packet travels all the way to the DAG root,
   which then sends it towards its destination using a source route."

Then it describes the storing mode operation

"In storing mode operation, if the destination is a DAG descendant and
   the source maintains "downwards" routing state about this descendant,
   it can forward the packet along this route.  Otherwise, the source
   sends the packet to a DAG parent, which then applies the same set of
   rules to forward the packet further."

I guess I could modify the first sentence as follows

"In storing mode operation, if the destination is a DAG descendant and
   the source maintains "downwards" HOP-BY-HOP routing state about this descendant,
   it can forward the packet along this route..."

Would this change be sufficient?

[Anders]
Since a given implementation is going to be either
non-storing or storing one may consider having
dedicated sections (or documents?) explaining
what is required for making a system work for
non-storing or storing mode, respectively.

[Mukul]

Are you suggesting that hop-by-hop P2P routes can not be used in an LLN using non-storing mode RPL operation? It seems to me that both types of P2P routes (hop-by-hop; source) can be used irrespective of whether core RPL operation is storing mode or non-storing mode.

Thanks
Mukul

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