Controlled Delay Active Queue Management
draft-ietf-aqm-codel-10

I think that this is a useful document - I also think that it would make a good introductory document to describe queuing for e.g a collage class. 

I do have some readability suggestions to make it even better; these do not need any action, but if the authors happen to edit the document for any other reason, they may want to address them.

1: I found the overall structure of the document a little odd -- I'm assuming that this is an artifact of its history, or merging multiple documents into one, or similar. It starts off with a nice description of queuing and CoDel. It then gets all technical with the pseudo-code (which was really helpful). Where it feels a little odd is that it then suddenly goes back to being much more introductory feeling (Section 5 - ), and feels like it repeats some of the earlier material. Reformatting it all to address this seems like overkill, but perhaps a readers note to suggest people who want more background should skip ahead then come back.

2: Section 1.  Introduction
- "determined set point derived from maximizing the network power metric" -- I'd suggest referencing Section 5.2 where power is explained (or, if we assume readers understand this, section 5.2 can be dropped).

3: Section 3.  Overview of the Codel AQM
Sojourn time is a really important concept in this document, but it isn't really defined - Section 5.1 is closest to defining it, but still not great.

4: Section 3.1
"The MTU size can be set adaptively to the largest packet seen so far or can be read from the driver."
It was unclear what driver -- perhaps "interface driver" or simply "interface"?

5: Section 3.2 has an opening parens but no closing one ("known or measure (though ...").
This is a tiny nit, but set off my OCD tendencies :-)

6: Section 5.1
"We use this insight in the  pseudo-code for CoDel later in the draft.)
 - earlier in the draft...

Section 5.2: 
AIMD TCP could use a reference.

Thank you for a clear and very well written document.  This was well worth staying up
past 1am to read fully.  I do have one primary comment and a couple minor points.

First, the document status is Experimental.   While encouraging experimentation, the
document doesn't really articulate what the concerns are or how experimentation might
determine that this should be changed to standards track.  While regrettably I haven't
personally followed the AQM work, I might assume that some of the issues to general
applicability might be tied to aspects around the challenges of applying CoDel to a 
system architecture built around WRED AQM and enqueue complexity rather than dequeue
complexity.  Having a paragraph that gave context in the introduction for the questions
still to be explored would be helpful.

a) In Sec 3.4 :  "This property of CoDel has been exploited in
   fq_codel [FQ-CODEL-ID], which hashes on the packet header fields to
   determine a specific bin, or sub-queue, for each five-tuple flow,"
  For the general case of traffic, it would be better to focus on using a microflow's
  entropy information  - whether that is derived from a 5-tuple, the IPv6 flow label, 
  an MPLS Entropy label, etc.  Tying this specifically to the 5-tuple is not ideal.
  Obviously I missed this for draft-ietf-aqm-fq-codel-06 - but even a slight rephrasing
to "for each microflow, identifiable via five-tuple hash, src/dest + IPv6 flow label, or
other entropy information" would encourage better understanding of micro-flow identification.
Of course, this is just a comment - so do with it what you will.

b) (Nit) In Sec 5.1: " We use this insight in the pseudo-code for CoDel later in the draft."
  The pseudo-code is actually earlier in the draft.  Also s/draft/document for publication.

Glad to see this document progress.

From Fernando's Gen-ART review:

* Page 17:
  simulation that this result holds for Reno, Cubic, and
  Westwood[TSV84].

Missing space.

I'm a strong Yes on this document, but encourage the authors to work through comments about readability from other ADs.