Summary: 
This document defines the Host Identity Protocol Diet EXchange (HIP
   DEX) protocol for constrained devices. The draft is well written. I believe it is ready for publication.
Major issue: None
Minor issue: Editorial
1.It is not clear how fine-grained policy control defined in IKEv2 is different from policy control defined in HIP DEX protocol? In the draft, local policies are mentioned many times, however it is not clear what local policy for HIP DEX Protocol looks like? Is it possbile to carry policy control parameters(e.g., ACL parameter) in the HIP DEX protocol message? Would it be great to provide example to clarify this.
2. Is Nonce I same as radom value #I?
3. Is puzzle difficulty K same as #K used in the HIP R1 described in section 7?
4. Is puzzle difficulty K same as low-order #K bits of the RHASH? If the answer is yes, please make the term and symbol used in the draft consistent.