Change:
increased in either slow start or congestion avoidance.  This can happen due to insufficient application data or flow control limits. <del> A sender can use the pipeACK method described in Section 4.3 of RFC7661 to determine if the congestion window is sufficiently utilized. </del> A sender that paces packets (see pacing) might delay sending packets and not fully utilize the congestion window due to this delay.  A sender SHOULD NOT consider itself application limited if it would

Discussion:
by removing a paragraph mentioning pipeACK and moving RFC3168 to a normative reference.
In Recovery-31 there are several references that I judge as normative and not informative ones. Section 7.8: "A sender MAY use the pipeACK method described in Section 4.3 of [RFC7661] to determine if the congestion window is sufficiently utilized." A normative reference necessary to follow if one selects to use the optional method.Sectiom 7.3.2: "Implementations MAY reduce the congestion window immediately upon entering a recovery period or use other mechanisms, such as Proportional Rate Reduction ([PRR]), to reduce the congestion window more gradually." Another case of a suggested mechanism, which if one is to follow it requires one to read that PPR reference. Secondly, why the alternative reference style.Section 8.3: "Markings can be treated as equivalent to loss ([RFC3168]), but other responses can be specified, such as ([RFC8511]) or ([RFC8311])." So RFC3168 is the normative specification for the treat it equal to loss. RFC8511 is the TCP alternative back-off an experimental specification for the alternative. And RFC8311 is the process for performing other experiments with alternative responses. I judge all necessary depending on what one intendeds to do. So to my understanding this results in two downrefs to experimental specifications. I think that is acceptable in the context they are used in this document. But to be tried in IETF last call. However, I think I don't want to generally recommend them to be acceptable as downrefs so I have no intentions to promote them for the Downref registry.
Moving discussion from the PR to the issue. NAME : I'm not the expert on what should be normative, but these were intentionally marked as informative references since they're all TCP specific RFCs. The pipeACK reference in particular seems like an odd one. If this is what the chairs want, then I'm ok with it as an editor, but these choices were intentional. NAME : I see what NAME is saying, but I also see some wiggle room in RFC 3967, Section 1.1: When a reference to an example is made, such a reference need not be normative.

For example, text such as "an algorithm such as the one specified in [RFCxxxx] would be acceptable" indicates an informative reference, since that cited algorithm is just one of several possible algorithms that could be used. I am also somewhat concerned that trying to get the downrefs into the registry is more likely to run into trouble (Sec 3) This procedure should not be used if the proper step is to move the document to which the reference is being made into the appropriate category. It is not intended as an easy way out of normal process. Rather, the procedure is intended for dealing with specific cases where putting particular documents into the required category is problematic and unlikely ever to happen.
Thanks for digging up the relevant text, NAME Based on that text from RFC 3967, it doesn't seem like we need to make these references normative. I agree that the pipeACK reference is odd, but I think that's probably because of the use of MAY there. I'm happy to replace the MAY with a can -- it is meant to present an option, not a permission -- and make that reference informative as well. NAME : thoughts?
I think at last RFC3168 should be referenced normatively somewhere (probably section 7.1 though) because you need to know what the ECN bits are in order to do anything with it. I guess because of section 7.1. RFC8311 should also be a normative reference.
NAME RFC3168 is already a normative reference in the transport doc, which in my view is appropriate.
Was wondering about this as well given the transport doc is of course a normative reference of this doc. However, as this doc uses terms like CE also directly itself I think the right practice is to also have it as a normative reference here, and as you have to read it no matter what, it definitely shouldn't hurt.
talks about ECN-CE markings, but really all of Section 7 talks about a response to an increase in ECN-CE count by the peer, which is defined in the transport doc. This does point to a small editorial issue. The text in Section 4.1 says: This really should be:
Good point on the editorial issue.
With that change, the only thing we're left with is .

This does require an understanding of ECN, and it has RFC 2119 keywords, but it's really an optional mechanism that is suggested. We could remove the RFC 2119 words there, since they're really unnecessary.
My point is that RFC3168 should be normative because not matter what you need to understand what an ECN-CE mark is and that is defined/specified in RFC3168.
Mirja has a point, see URL
-transport is a normative reference. So 3168 is already (transitively) a normative reference. The question is whether this specific text requires anything from 3168 to understand. I don't see that it does, especially given the suggested change, which talks about a concept defined in -transport, not 3168.
has made these editorial changes; NAME can you see if anything else needs to be done here?
I will note that it was never my intention to let any of theses Experimental or informational TCP specs to be added into the downref registry by this last call. So, the pipeack reference needs to be reformulated to not be a normative one. As currently stated it is a clear normative reference per IESG Statement ([URL]) , and especially "Note 1: Even references that are relevant only for optional features must be classified as normative if they meet the above conditions for normative references. " You need to find a formulation that normative describes what the implementation MAY do, and then you can exemplify with the TCP version. Then one in Section 7.3.2 I can accept as still being informative as the MAY statement is related to the primary aspect of the sentence and the reference to PPR is exemplifying. Still this is very much on the border and may still generate a comment in IESG. For RFC 3168 I don't understand why not making it to a normative one. There are no issues with its status as it is proposed standard. And simply the security consideration section still implies that you need to know what a ECN-CE mark is to interpret this. So please make this one normative.
I'm ok with RFC 3168 being normative, particularly since it's already normative in transport, but would like to avoid making the others normative.

NAME if pipeack is not normative then a reformulation is necessary of that sentence in Section 7.8 to not state is as a mechanism that MAY be implemented.
The sentence currently has a can, not a MAY: "A sender can use the pipeACK method described in Section 4.3 of {{?RFC7661}} to determine if the congestion window is sufficiently utilized." But I sent out PR to make it clearer that pipeACK is an example, PTAL and see if that helps.
NAME what PR proposes removing that first sentence do resolve the pipeack to me. So merging , and moving RFC3168 to normative will resolve this issue to my understanding.
Thanks! I'll update PR to include moving RFC3168 to normative.
NAME NAME : I believe this is purely editorial, but I'd like to confirm.
We've meandered to a route that AFAICT makes reference types accurate to their existing intent, or avoids them becoming normative. I'm happy for this to be editorials.