Subject: [Roll] Section 5.4 in RPL-01 draft (DAG discovery)

From: Mukul Goyal <[email-masked]>
Date: Sat, 19 Sep 2009 13:44:37 -0500 (CDT)

Hi all,

The first 3 rules in Section 5.4 need clarification:

"   1.   A node that does not have any DAG parents in a DAG is the root
        of its own floating DAG.  It's rank is 1.  A node will end up in
        that situation when it looses all of its current feasible
        parents, i.e. the set of DAG parents becomes depleted.  In that
        case, the node SHOULD remember the DAGID and the sequence
        counter in the DIO of the lost parents for a period of time
        which covers multiple DIO."

   2.   A LLN Node that is attached to an infrastructure that does not
        support DIO, is the DAG root of its own grounded DAG.  It's rank
        is 1.

   3.   A router sending a RA without DIO is considered a grounded
        infrastructure at rank 0.  (For example, a router that is in
        communication with an LLN node but not running RPL such as a
        backbone router in communication with an LBR)"

Questions:

1. The first question is whether a DAG root has rank 0 or 1. Section 5.1.1 (page 35) says that a DAG root will have rank 0 but the rules in sec 5.4 contradict that.

2. What is the point behind rule 2? Why consider a node that does not understand DIO as a DAG?

3. Suppose an RPL router (an LLN node) does not include any DIO in its RA. As per rule 3 above, it will be considered part of a grounded infrastructure???

Thanks
Mukul

3.