Re: [Roll] multicast DAO

[Philip Levis <pal at cs.stanford.edu>]

On Oct 28, 2009, at 9:29 AM, Julien Abeille (jabeille) wrote:

> Hi all,
>
> regarding usage of multicast DAO: in the following scenario:
>   A
>  /  \
> B  C
>
> if the purpose is to to allow B and C to talk to each other  
> directly, the multicast DAO is equivalent to an unsolicited NA.
>
> In the scenarios like:
>
>    A
>   /  \
> B   C
>       |
>       D
> if the purpose is to have B talk to D through C (instead of A then  
> C), then the multicast DAO (including destination prefix option)  
> makes sense.
> Is this scenario needed by some applications?

Julien,

The text in -04 reads:

"The objective [of multicast DAOs] is to enable direct P2P  
communication, between destinations directly supported by neighboring  
nodes, without needing the RPL routing structure to relay the packets."

So the case it's concerned with is the latter one: B to C to D.  
Clearly one could use NA for the B-C case.

Point-to-point communication between nodes is needed by some  
applications. Section 5.2.2 of draft-ietf-roll-building-routing-reqs-07:

"A network device MUST be able to communicate in a point-to-point  
manner with any other device on the network."

Do you agree? Is it OK to resolve this ticket?

Phil