Subject: [Roll] confusion regarding relationship between DAG rank and OCP

From: Mukul Goyal <[email-masked]>
Date: Sat, 19 Sep 2009 12:06:44 -0500 (CDT)

Section 5.4 page 43 (rpl-01)

"One of these information, the DAG rank, is used by DAG Discovery to
   provide loop avoidance even if nodes implement different policies.
   The DAG Rank is computed as specified by the Objective Code Point in
   use by the DAG, demonstrating the properties described in
   Section 3.4.1.  The rank should be computed in such a way so as to
   provide a comparable basis with other nodes which may not use the
   same metric at all."

I am a little confused by the paragraph above. I thought OCP will specify the relevant routing metrics and how to calculate DAG rank as a function of these metrics. So the DAG rank is tightly tied to specific routing metrics and policies. 

The paragraph above gives the impression that DAG rank should be somewhat independent of routing policies/metrics.

Thanks
Mukul