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. I agree with the comments raised by the genart review by Theresa Enghardt. The Security Section is just a reference to another document that specifies in its own Security Consideration: As explained in Section 5, SCHC is expected to be implemented on top of LPWAN technologies, which are expected to implement security measures. This document explains that packets are wrapped in CoAP and then this document can be used to compress fields, similar to the references document. But now this is happening in the most outer layer, which the referenced document basically states that in its Security Considerations, it assumes the outer layer has some kind of LPWAN based security meassures in place. It seems these two drafts need some coordination to determine where, how and which Security Considerations are relevant. Additionally, I'm a bit worried about multiple layers doing compression. Can this lead to security issues? If not, why not? Where is it sais that compression states need to be checked for bogus instructions? How are these prevented? Think of the ever-decompressing zip file hacks of the past. How are these DoS attacks prevented ? Other than this issue, I found Section 1 Introducion a bit confusing. It seems to drop a reference to another document and then explain that other document, without really talking about this document? Or if it does, it was not very clear to me. I did not review this document for nits - my apologies but I ran out of time.