A  nit:

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 Ready With Nits.

This draft concerns MPLS Network Actions (MNA) technologies.  MNA technologies are used to indicate actions that impact  forwarding or other processing of the packet along the Label Switched Path (LSP)and to transfer any additional information needed for such processing.   They are generally carried in sub-stacks within the MPLS label stack.   This document describes requirements on solutions, and an architecture is proposed that is intended to capture best practices.  If a practice has issues but also has benefits, the issues are pointed out, but the practice is not discouraged; instead mitigations are suggested.

I think this is a good approach to the topic, and the draft gives helpful advice that deserves to be  captured in an Informational RFC. 


The same is true for a BIER payload as for any use of the first nibble: it is
not possible to conclude that the payload is BIER even if the first
nibble is set to 5 because an Ethernet pseudowire without a control
word might begin with a 5. However, the BIER approach meets the
design goal of [RFC8296] to determine that the payload is IPv4, IPv6
or a pseudowire using a control word.


I think that that last should “a pseudowire not using a control word”