Subject: [Roll] Comment about RPL nodes joining the all-rpl multicast address

From: Alexandru Petrescu <[email-masked]>
Date: Tue, 03 Aug 2010 09:43:04 +0200

Comments about RPL nodes joining the all-rpl multicast address

Are the RPL nodes in RPL -11 document joining the all-rpl multicast address?

I think the spec should say so, otherwise they won't receive the
messages sent to it.

The closest I could find is this:
> As is traditional, a listener uses a protocol such as MLD with a
> router to register to a multicast group.

Is there some more specific text about joining that group?

I think the spec should be clearer and require the node to join this
multicast group, with the explicit name of all-rpl nodes. It could leave
the method of joining as MAY (e.g. MLD, or setting up local filters).

Example text: "all RPL nodes MUST join the multicast group all-rpl
nodes.  This operation MAY be realized with MLDv2, local filters, or
other method".

(without joining the group, the message is not delivered to it).

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In addition, it may be advantageous for an RPL node to join the
solicited-node multicast address, and send DIS to it.  For example,
current text says:
> The DODAG Information Solicitation (DIS) message may be used to
> solicit a DODAG Information Object from a RPL node.  Its use is
> analogous to that of a Router Solicitation as specified in IPv6
> Neighbor Discovery

Ok, RS is some times sent to the solicited-node multicast address - will
the DIS too?

Alex