Reviewer: Carlos Pignataro Review Result: Has Nits I have reviewed this document as part of the Operational directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written with the intent of improving the operational aspects of the IETF drafts. Comments that are not addressed in last call may be included in AD reviews during the IESG review. Document editors and WG chairs should treat these comments just like any other last call comments. I hope these comments are useful and clear. From an operational point of view, the document describes protocol interactions for dealing with failure conditions, and sets default behaviors. For example, the RFC 2119 language explaining the use of is super useful. Minor comments, questions, and nits for your consideration follow: 1. Section 2 -- Migrating to Newer Versions of This Extension (Note to RFC Editor: remove this section before publication as an RFC.) Since forward compatibility is a key operational consideration, why should this section be removed? Especially when it contains RFC 2119 language. 2. Please do not treat as a pedantic comment, but I did not see an actual definition for what "fee" and "credit" mean. Since these words have specific context, it might not hurt to have a formal definition in Section 1.1 3. Should the citation / reference for "ISO 4217" be "ISO 4217:2015"? 4. S3.4. Does this text imply there is no zero fee or credit possible? Might be useful to explicitly set guidance for the use of 0/null fee/credit. A element MUST have a non-negative value. A element MUST have a negative value. 5. S3.6, why "equal to" and not only "exceed"? A server MAY reject certain transactions if the absolute value of the is equal to or exceeds the value of the element. 6. Section 6.1 * Should and markers be used as per the TLP? * Should the (c) year be 2019? * And should the BSD License be part of the code? 7. Section 7, Security Considerations. What are "security services"? Further, this protocol deals with on-the-wire monetary information. I suspect there might be specific such considerations. 8. Section 9. Implementation Status If this section is removed, the reference to [RFC7942] would result hanging without citations to it. ALthough the RFC Editor would catch, might want to indicate removal of the Normative Reference as well. Thanks! Carlos Pignataro.