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.

The summary of the review is the document is ready.

This is a short document that describes how to encode features in the SenML version.  The document is clear, I don't see any security.  The encoding features in a version string will cause some confusion, but this is pointed out.