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 guidance on composing path metrics from sub-path metrics within the IP Performance Metrics framework. I am not an expert on IPPM but after some analysis I have concluded that the security considerations in this draft are adequate. They raise all the relevant security issues that I could come up with and provide guidance for how those issues can be addressed.