Hi, I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. Document editors and WG chairs should treat these comments just like any other last call comments. This document describe an abstract mechanism for senders to inform a network about congestion encountered by packets over a flow by adding ConEx (Congestion Exposure) Signals. It is part of a set of documents for which the entry point is RFC 6789. Security Considerations (Ready): >From a security considerations point of view, I think this document is Ready for publication. It correctly identifies the main security considerations as the robustness of congestion marking and auditing so that malefactors cannot gain advantage from cheating. While real security details are necessarily deferred to specific ConEx specifications, this abstract specification document in my opinion does a good job of discussing, in general terms, the threats and a number of strategies to defend against them. Comment: I found some of the wording to be a bit confusing. For example, the first sentence in the abstract is as follows: "This document describes an abstract mechanism by which senders inform the network about the congestion encountered by packets earlier in the same flow." and the first sentence of the Introduction is very similar. But, if I understand Figure 1 correctly, what is abstractly specified is the addition to data flowing from from A to B of information about congestion encountered over the entire A to B path, not "earlier in the same flow". Perhaps my understanding is confused, but that would also indicate a lack of clarity. Nits: Section 2, bottom of page 4: "... to be able apply sufficient ..." -> "... to be able to apply sufficient ...". In a number of Sections there are what are, in effect, sub-heading indicated by a word or two followed by a colon and then text indented by three spaces. In some cases, this is used with no blank lines, which is fine. However, in other cases this indented text is has multiple paragraphs separated by a blank line. In most such instances, there is also a blank line before each such "sub-heading", for example Section 5.5. But not in Section 6, which looks odd in some places as a result. I suggest having a blank line before such sub-headings in Section 6. Thanks, Donald ============================= Donald E. Eastlake 3rd +1-508-333-2270 (cell) 155 Beaver Street, Milford, MA 01757 USA d3e3e3 at gmail.com