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. This document is about using the CoAP protocol (constrained application protocol) for sensors, and focuses on saving power. As it correctly points out, there really are no security issues with what is discussed in this draft.  If they wanted, they could say that not constantly pinging in order for the network to find you not only saves power (if all you want to do is send messages when you want to rather than being reachable for receiving messages), but also could be seen as a privacy enhancement. Typo, first line of page 5.  "For economical reasons..." should probably be "For economic reasons" Radia