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

Hi Mukul

(see inline)

Cheers,
  Anders 

> -----Original Message-----
> From: Mukul Goyal [mailto:mukul@uwm.edu] 
> Sent: Wednesday, November 17, 2010 20:48
> To: Anders Brandt
> Cc: ROLL WG
> Subject: Re: [Roll] RPL P2P - Clarify that hop-by-hop is 
> identical to RPLStoring mode
> 
> 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]

Yes, this definitely helps. But the last part
" ...forward the packet along this route."
seems to mix things up.

May I suggest:
" ...forward the packet to a descendant router closer to the
destination..."

> [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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