I had the draft authors’ email address wrong on my last message, so I am resending it. 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 gives recommendations for the use of RPL in home automation and building control, that typically provide support such things as climate and lighting control.  I reviewed a much earlier version of this document, and I think this version is much improved in the way it scopes out the problem and handles the security implications.  The Security Considerations section in particular is very thorough.  There are a few improvements I would recommend, however: Section 4.1.8   Security You should  give justifications for these choices of parameters as you give justifications for the other parameters described in this draft. Section 7.1 Security considerations during initial deployment New approaches to initial security deployment are being developed in    [I-D.kumar-dice-dtls-relay] and    [I-D.richardson-6tisch--security-6top].  They assume a partial    ordering of the nodes, such that unsecured nodes are added    sequentially with the restriction that a path between two secured    nodes exists which passes through secured nodes only. I found this a little hard to understand.  When does a node pass from being unsecured to secured?  Or does an unsecured node remain unsecured? If there is a succinct way of saying this, it could go here.  Since this is only describing new approaches that could potentially be applied, you would not want to go into a lot of detail.  In the home, nodes can be visually inspected by the home owner    and simple measures like pushing buttons simultaneously on joint and    joining devices is probably sufficient. I think this definitely needs to be clarified!  You need to say what is being accomplished by pushing the buttons (device pairing)? 7.2 When nodes are lost, no additional security measures are needed, the    network remains secure as before by not allowing the addition of new    nodes. I’m not sure what this means.  Does it mean that if a node is lost, then it is treated as a “new node” if it reappears, and is not allowed to rejoin the network? New nodes can be added by using the same protocols used for    initial deployment. This came right after the sentence beginning “When nodes are lost” which said that new nodes are not added.  That contradiction needs to be reconciled.  I’m also not sure what “using the same protocol” means.  Does it mean rerunning the protocol and rekeying all the nodes, or does it mean using the features that protocol has for adding nodes? Nits: Section 1.1  This applicability statement    recommends more light weight security solutions and specify the    conditions under which these solutions are appropriate. Should be “specifies” instead of “specify”.  I’m also not sure what is meant by “conditions under which these solutions are appropriate.”  Do you mean light-weight as opposed to no security, or light-weight as opposed to heavy-weight.  Or are you talking about conditions under which different light-weight solutions are appropriate? From reading the rest of the draft, I would assume the last is what you mean. I consider this document  ready with issues. Catherine Meadows Naval Research Laboratory Code 5543 4555 Overlook Ave., S.W. Washington DC, 20375 phone: 202-767-3490 fax: 202-404-7942 email:  catherine.meadows at nrl.navy.mil