Last Call Review of draft-ietf-roll-routing-metrics-
review-ietf-roll-routing-metrics-secdir-lc-salowey-2011-01-10-00

I have reviewed this document as part of the security directorate's
ongoing effort to review all IETF documents being processed by the
IESG.  These comments were written primarily for the benefit of the
security area directors.  Document editors and WG chairs should treat
these comments just like any other last call comments.

In general I think the document is clear.  I have one security related issue. 
The security considerations mention attacks where the metric information is
manipulated to cause problems.  I think there may also be cases where
disclosure of some of the metric information may be an issue.  the main area of
concern for me is the node energy metric.  This information may be useful to an
attacker to determine which devices to attack with out-of-band or in-band
attacks involving energy draining.   I have not had a chance to see if the RPL
protects the confidentiality of these attributes.  If this is a concern in a
deployment environment then the usage of these attributes may be limited.   I
think it is probably worth mentioning this in the security considerations.

Also energy metric introduce a new vector into the system for an attacker to
modify routing behavior.  An attacker can purposely attempt to modify the
stored energy in a node to modify the metrics advertised.   Its not clear to me
at this point if this is significant since the power drain may have effect on
metrics and routing beyond what is advertised and it seems the recommendation
to protect against unstable links would be effective in this case as well.

Cheers,

Joe