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. Status: Ready with nits. This document discusses networks comprised of constrained nodes (i.e. nodes with limited power, CPU, storage, etc.). It does cover whether various classes of nodes can participate in secure networks, which is good, but the Security Considerations section is empty - I would suggest that this section could usefully contain a summary of the security implications of the various constraints discussed.