Proportional Integral Controller Enhanced (PIE): A Lightweight Control Scheme to Address the Bufferbloat Problem
draft-ietf-aqm-pie-10

Received changes through RFC Editor sync (changed abstract to 'Bufferbloat is a phenomenon in which excess buffers in the network cause high latency and latency variation. As more and more interactive applications (e.g., voice over IP, real-time video streaming, and financial transactions) run in the Internet, high latency and latency variation degrade application performance. There is a pressing need to design intelligent queue management schemes that can control latency and latency variation, and hence provide desirable quality of service to users.

This document presents a lightweight active queue management design called "PIE" (Proportional Integral controller Enhanced) that can effectively control the average queuing latency to a target value. Simulation results, theoretical analysis, and Linux testbed results have shown that PIE can ensure low latency and achieve high link utilization under various congestion situations. The design does not require per-packet timestamps, so it incurs very little overhead and is simple enough to implement in both hardware and software.')

Received changes through RFC Editor sync (created alias RFC 8033, changed title to 'Proportional Integral Controller Enhanced (PIE): A Lightweight Control Scheme to Address the Bufferbloat Problem', changed abstract to 'Bufferbloat is a phenomenon in which excess buffers in the network cause high latency and latency variation. As more and more interactive applications (e.g., voice over IP, real-time video streaming, and financial transactions) run in the Internet, high latency and latency variation degrade application performance. There is a pressing need to design intelligent queue management schemes that can control latency and latency variation, and hence provide desirable quality of service to users.', changed pages to 30, changed standardization level to Experimental, changed state to RFC, added RFC published event at 2017-02-28, changed IESG state to RFC Published)

[Ballot comment]
Is this text

    The decay parameter of 2% gives us around 750ms time constant, a few RTT.
   
assuming a particular network technology and/or topology?

[Ballot comment]
- Support Ben's comment:

It would be nice to see some text about the nature of the "experiment".
That is, why is this experimental? Do you expect to promote this to a
standard in the future? (The shepherd's report speaks of this; the draft
should, too)

ex: https://tools.ietf.org/html/rfc6614#section-1.3

- Minor personal preference: delay variation instead of jitter.
See https://tools.ietf.org/html/rfc5481#section-1 for a justification.
Btw, same comment for draft-ietf-aqm-eval-guidelines-11, which I forgot to mention.

- Section 1
RFC2309 is obsolete:

  RFC 2309[RFC2309]
  strongly recommends the adoption of AQM schemes in the network to
  improve the performance of the Internet.

Not sure why [RFC2309] is different than [IETF-AQM], which is now RFC7567. So maybe using [RFC2309] was used on purpose.


- it seems that you sometimes interchange queueing latency, latency, delay, queue delay
For an example, review section 3 and section 4 first paragraph.
You should really use consistent terms, for example queueing latency, throughout the document.

OLD:

As illustrated in Fig. 1, PIE conceptually comprises three simple MUST
components: a) random dropping at enqueueing; b) periodic drop
probability update; c) latency calculation. When a packet arrives, a
random decision is made regarding whether to drop the packet. The drop
probability is updated periodically based on how far the current delay
is away from the target and whether the queueing delay is currently
trending up or down. The queueing delay can be obtained using direct
measurements or using estimations calculated from the queue length and
the dequeue rate.

NEW:
As illustrated in Fig. 1, PIE conceptually comprises three simple MUST
components: a) random dropping at enqueueing; b) periodic drop
probability update; c) queueing latency calculation. When a packet arrives, a
random decision is made regarding whether to drop the packet. The drop
probability is updated periodically based on how far the current queueing latency
is away from the target and whether the queueing latency is currently
trending up or down. The queueing latency can be obtained using direct
measurements or using estimations calculated from the queue length and
the dequeue rate.


NEW:

        Random Drop
            /              --------------
    -------/  -------------->    | | | | | -------------->
            /|\                  | | | | |
            |              --------------
            |            Queue Buffer  \
            |                    |      \
            |                    |queue  \
            |                    |length  \
            |                    |          \
            |                    \|/        \/
            |          -----------------    -------------------
            |          |    Drop      |    | Queueing        |
            -----<-----|  Probability  |<---| Latency        |
                        |  Calculation  |    | Calculation    |
                        -----------------    -------------------



- terminology: dequeue_rate or departure?
    Section 4.2 =>"dequeue rate"
    Section 4.3

        current_qdelay = queue_.byte_length()/dequeue_rate;

    Section 5.2 Departure Rate Estimation
    Section 5.2 typo "Upon a packet deque:"  (this one could fine if you speak about the
                                                                      deque(Packet packet) function, but that's not clear)
Again, be consistent across the entire doc.

- editorial: missing reference links

  CBQ has been a standard feature in most network devices today[CBQ].

    The controller parameters, alpha and beta(in the unit of hz) are
    designed using feedback loop analysis where TCP's behaviors are modeled
    using the results from well-studied prior art[TCP-Models].


- editorial:

  This draft separates the PIE design into the basic elements that are
  MUST to be implemented and optional SHOULD/MAY enhancement elements.

NEW:
  This draft separates the PIE design into the basic elements that
  MUST to be implemented and optional SHOULD/MAY enhancement elements.




Below is Mahesh's OPS DIR review:
I have reviewed the following 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.

Document reviewed:  draft-ietf-aqm-pie-06

Summary: Ready with nits.

    The document is on an Experimental Track. Perhaps because of it there is little discussion of either operational or management considerations. If the document progresses towards a standardization effort, the following are (only a partial list of) suggestions or areas that can be explored.
    From a deployment consideration perspective
        The document could talk about how the technology is going to be deployed or managed.
        It would help if the authors documented any scaling issues that they have run into.
        How would this AQM co-exist with other methods?
    From an installation and initial setup perspective
        The document could talk about how PIE would be configured. For the parameters that are configurable, what are the ranges and what is the default value.
        Are the parameters going to be configured by configuration manager, or will the device pull the configuration from a configuration server?
    From a network operations perspective
        The document could talk about the impact of PIE on existing networks, with or without other AQM.
        While PIE attempts to reduce latency and jitter, what is the impact on throughput when it is deployed, specially for non-real time traffic?
    From a verifying correct operations perspective
        How does one verify that the network is behaving as expected once PIE is applied?
        Other than latency and jitter, are there any other parameters of interest?
        Will the test in itself have an impact on the network or the protocol?
    From a management interoperability perspective
        The document can talk about any standard YANG models that might need to be enhanced or developed for manageability across vendors.
    From a fault or threshold conditions perspective
        The document could talk about any notifications that need to be reported for any events generated because of the algorithm. Should the events be polled or could they be pushed? Would notifications have to be throttled?


A run of idnits has revealed a few issues that will need to addressed.

tmp/draft-ietf-aqm-pie-06.txt:
tmp/draft-ietf-aqm-pie-06.txt(17): Found control character TAB in position 1.
tmp/draft-ietf-aqm-pie-06.txt(383): Found control character TAB in position 4.
tmp/draft-ietf-aqm-pie-06.txt(469): Found control character TAB in position 9.
tmp/draft-ietf-aqm-pie-06.txt(471): Found control character TAB in position 9.
tmp/draft-ietf-aqm-pie-06.txt(941): Line is too long: the offending characters are '.'
tmp/draft-ietf-aqm-pie-06.txt(978): Found control character TAB in position 8.
tmp/draft-ietf-aqm-pie-06.txt(982): Found control character TAB in position 9.
tmp/draft-ietf-aqm-pie-06.txt(1099): Found control character TAB in position 7.
tmp/draft-ietf-aqm-pie-06.txt(1101): Found control character TAB in position 7.
tmp/draft-ietf-aqm-pie-06.txt(1112): Found control character TAB in position 4.
tmp/draft-ietf-aqm-pie-06.txt(1126): Found control character TAB in position 4.
tmp/draft-ietf-aqm-pie-06.txt(1128): Found control character TAB in position 4.
tmp/draft-ietf-aqm-pie-06.txt(1182): Found control character TAB in position 9.
tmp/draft-ietf-aqm-pie-06.txt(1187): Found control character TAB in position 9.
tmp/draft-ietf-aqm-pie-06.txt(1189): Found control character TAB in position 9.
tmp/draft-ietf-aqm-pie-06.txt(1253): Found control character TAB in position 7.
tmp/draft-ietf-aqm-pie-06.txt(1254): Found control character TAB in position 7.
tmp/draft-ietf-aqm-pie-06.txt(1257): Found control character TAB in position 7.
tmp/draft-ietf-aqm-pie-06.txt(1258): Found control character TAB in position 13.
tmp/draft-ietf-aqm-pie-06.txt(1259): Found control character TAB in position 7.
tmp/draft-ietf-aqm-pie-06.txt(1260): Found control character TAB in position 13.
tmp/draft-ietf-aqm-pie-06.txt(1261): Found control character TAB in position 13.
tmp/draft-ietf-aqm-pie-06.txt(1263): Found control character TAB in position 7.
tmp/draft-ietf-aqm-pie-06.txt(1306): Found control character TAB in position 4.
tmp/draft-ietf-aqm-pie-06.txt(1325): Found control character TAB in position 7.
tmp/draft-ietf-aqm-pie-06.txt(1327): Found control character TAB in position 4.
tmp/draft-ietf-aqm-pie-06.txt(1328): Found control character TAB in position 4.
tmp/draft-ietf-aqm-pie-06.txt(1330): Found control character TAB in position 4.
tmp/draft-ietf-aqm-pie-06.txt(1352): Found control character TAB in position 4.
tmp/draft-ietf-aqm-pie-06.txt(1386): Found control character TAB in position 9.
tmp/draft-ietf-aqm-pie-06.txt(1391): Found control character TAB in position 9.
tmp/draft-ietf-aqm-pie-06.txt(1393): Found control character TAB in position 9.


[Stuff deleted]

  Checking boilerplate required by RFC 5378 and the IETF Trust (see
  http://trustee.ietf.org/license-info):
  ----------------------------------------------------------------------------

    No issues found here.

  Checking nits according to http://www.ietf.org/id-info/1id-guidelines.txt:
  ----------------------------------------------------------------------------

    No issues found here.

  Checking nits according to http://www.ietf.org/id-info/checklist :
  ----------------------------------------------------------------------------

  ** There is 1 instance of too long lines in the document, the longest one
    being 1 character in excess of 72.

  ** There are 31 instances of lines with control characters in the document.


  Miscellaneous warnings:
  ----------------------------------------------------------------------------

  == The copyright year in the IETF Trust and authors Copyright Line does not
    match the current year


  Checking references for intended status: Experimental
  ----------------------------------------------------------------------------

  == Missing Reference: 'IETF-AQM' is mentioned on line 748, but not
    defined
    '[IETF-AQM]    Baker, F. and Fairhurst, G., "IETF Recommendations...'

  == Missing Reference: 'CoDel' is mentioned on line 730, but not
    defined
    '[CoDel]        Nichols, K., Jacobson, V., "Controlling Queue Dela...'

  == Missing Reference: 'CBQ' is mentioned on line 727, but not
    defined
'[CBQ]          Cisco White Paper,...'

  == Missing Reference: 'FQ-Implement' is mentioned on line 739, but not
    defined
    '[FQ-Implement] Baker, F. and Pan, R. "On Queueing, Marking and...'

  == Missing Reference: 'DOCSIS-PIE' is mentioned on line 736, but not
    defined
    '[DOCSIS-PIE]  White, G. and Pan, R., "A PIE-Based AQM for DOCSIS...'

  == Missing Reference: 'HPSR-PIE' is mentioned on line 742, but not
    defined
    '[HPSR-PIE]    Pan, R., Natarajan, P. Piglione, C., Prabhu, M.S.,...'

  == Missing Reference: 'PI' is mentioned on line 755, but not defined
    '[PI]           Hollot, C.V., Misra, V., Towsley, D. and Gong, W.,...'

  == Missing Reference: 'QCN' is mentioned on line 759, but not
    defined
'[QCN]   "Data Center Bridging - Congestion Notification",...'

  == Missing Reference: 'TCP-Models' is mentioned on line 762, but not
    defined
    '[TCP-Models]  Misra, V., Gong, W., and Towsley, D., "Fluid-base...'

  == Missing Reference: 'IETF-ECN' is mentioned on line 751, but not
    defined
'[IETF-ECN]    Briscoe, B. Kaippallimalil, J and Phaler, P.,...'

  -- Obsolete informational reference (is this intentional?): RFC 2309
    (Obsoleted by RFC 7567)


    Summary: 2 errors (**), 0 flaws (~~), 11 warnings (==), 2 comments (--).

[Ballot comment]
In section 5 and its children: Please keep in mind that "SHOULD" does not mean quite the same thing as "optional".

It would be nice to see some text about the nature of the "experiment". That is, why is this experimental? Do you expect to promote this to a standard in the future? (The shepherd's report speaks of this;  the draft should, too.)

[Ballot comment]
Section 4.1:
QDELAY_REF is used here without definition. Suggest something like:

s/is smaller than half of QDELAY_REF/is smaller than half of the
target delay value (QDELAY_REF)/

Section 4.2:

Not sure what this piece of pseudo-code intends to achieve. Isn't this a no-op?

        } else {
            p = p;
        }

Section 5.3:

What does the following text intend to say? Do you mean when it is turned off?

"When PIE is optionally turned on and off, ..."

Section 5.4:

The forced drop at 8.5/PIE->drop_prob_ packets is not consistent
with the pseudo-code in page 24. The drop_early() does not the
drop packets if the queue is not congested. Either the
pseudo-code or text in this section needs to be adjusted.

[Ballot comment]
Thanks for doing this work.

In 4.2 and 4.4, it might help to explain how the default values were chosen, or point to where those are explained elsewhere.

[Ballot comment]

- Thanks to the IPR declaring folks for not using the term
"standard" in their declaration. (I first looked at one of
the earlier ones [1] that did say that, and I was about to
start my usual whine when I noticed the most recent one [2]
doesn't have that problem:-)

  [1] https://datatracker.ietf.org/ipr/2123/
  [2] https://datatracker.ietf.org/ipr/2540/

- Seems odd to mention one specific vendor in the security
considerations section. Why is that important to include?

(Via drafts-lastcall-comment@iana.org): IESG/Authors/WG Chairs:

IANA has reviewed draft-ietf-aqm-pie-07.txt, which is currently in Last Call, and has the following comments:

We understand that this document doesn't require any IANA actions.

While it's often helpful for a document's IANA Considerations section to remain in place upon publication even if there are no actions, if the authors strongly prefer to remove it, IANA does not object.

If this assessment is not accurate, please respond as soon as possible.

Thank you,

Sabrina Tanamal
IANA Specialist
ICANN

As required by RFC 4858, this is the current template for the Document
Shepherd Write-Up.

Changes are expected over time. This version is dated 24 February 2012.

(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)?  Why
is this the proper type of RFC?  Is this type of RFC indicated in the
title page header?


The document is targeted for Experimental.  This was the result of discussion in the working group.  The initial target had been a Proposed Standard, but the level of support for this by the end of the working group process was not high.  There have been good results from studies and deployments so far, and there is no reason to believe this would be harmful to deploy, so the working group believes that greater experimentation with PIE on the Internet should be encouraged, and that it might be a candidate for standardization later.


(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:

Technical Summary

  Relevant content can frequently be found in the abstract
  and/or introduction of the document. If not, this may be
  an indication that there are deficiencies in the abstract
  or introduction.

Abstract:
"""
  Bufferbloat is a phenomenon where excess buffers in the network cause
  high latency and jitter. As more and more interactive applications
  (e.g. voice over IP, real time video streaming and financial
  transactions) run in the Internet, high latency and jitter degrade
  application performance. There is a pressing need to design
  intelligent queue management schemes that can control latency and
  jitter; and hence provide desirable quality of service to users.

  This document presents a lightweight active queue management design,
  called PIE (Proportional Integral controller Enhanced), that can
  effectively control the average queueing latency to a target value.
  Simulation results, theoretical analysis and Linux testbed results
  have shown that PIE can ensure low latency and achieve high link
  utilization under various congestion situations. The design does not
  require per-packet timestamp, so it incurs very small overhead and is
  simple enough to implement in both hardware and software.
"""

Working Group Summary

  Was there anything in WG process that is worth noting? For
  example, was there controversy about particular points or
  were there decisions where the consensus was particularly
  rough?

There were no matters of large controversy, though there have been some criticisms of PIE.  The IPR did not seem to be a blocking point for anyone, but some participants prefered algorithms free of IPR.  There are multiple algorithms that were proposed to the AQM working group, and there are still some developing.  Some aspects of the PIE design were critiqued, and there are some identified matters for future research, but there did not seem to be any disagreement that this is useful to publish at this time.  It is understood that this does not block other algorithms or improvements from happening.  The critical reviews are useful in understanding the differences with other algorithms, and making improvements to PIE while in experimental stage.


Document Quality

  Are there existing implementations of the protocol? Have a
  significant number of vendors indicated their plan to
  implement the specification? Are there any reviewers that
  merit special mention as having done a thorough review,
  e.g., one that resulted in important changes or a
  conclusion that the document had no substantive issues? If
  there was a MIB Doctor, Media Type or other expert review,
  what was its course (briefly)? In the case of a Media Type
  review, on what date was the request posted?


Yes, there are multiple existing implementations, including in simulations, Linux, FreeBSD, and some may be based on description in the DOCSIS specification.  All of the implementation experience was helpful in improving the document quality and clarity when describing the algorithm.  A very thorough technical review was done by Bob Briscoe, and posted as a complete document itself.


Personnel

  Who is the Document Shepherd? Who is the Responsible Area
  Director?

Wesley Eddy (wes@mti-systems.com) is the document shepherd, and Mirja Kühlewind (ietf@kuehlewind.net) is the AD.


(3) Briefly describe the review of this document that was performed by
the Document Shepherd.  If this version of the document is not ready
for publication, please explain why the document is being forwarded to
the IESG.


I have reviewed the complete document multiple times.  It is ready for the IESG.


(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?


No concerns.


(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that
took place.


N/A


(6) Describe any specific concerns or issues that the Document Shepherd
has with this document that the Responsible Area Director and/or the
IESG should be aware of? For example, perhaps he or she is uncomfortable
with certain parts of the document, or has concerns whether there really
is a need for it. In any event, if the WG has discussed those issues and
has indicated that it still wishes to advance the document, detail those
concerns here.


No concerns.  Going to Experimental is, it seems, agreeable to the working group.  There might have been concerns (e.g. based on Bob Briscoe's review, or IPR) if targeting Proposed Standard.


(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why.


Yes.  There is IPR disclosed by Cisco, and tracked properly in the IETF system.  The working group has been aware of this.  After WGLC, 2 of the authors explicitly confirmed that all necessary disclosures have been made (the others did not reply).  All authors work for the same company (Cisco).


(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
disclosures.


Yes.  The working group reviewed the IPR disclosure and understands it.


(9) How solid is the WG consensus behind this document? Does it
represent the strong concurrence of a few individuals, with others
being silent, or does the WG as a whole understand and agree with it? 


The consensus seems solid.


(10) Has anyone threatened an appeal or otherwise indicated extreme
discontent? If so, please summarise the areas of conflict in separate
email messages to the Responsible Area Director. (It should be in a
separate email because this questionnaire is publicly available.)


No threats or indications of discontent.


(11) Identify any ID nits the Document Shepherd has found in this
document. (See https://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
thorough.


There are only a couple very small formatting nits that will be fixed by the RFC Editor easily.  The nits reported about references seem to be spurious, and probably result from the use of an "other references" section which the RFC Editor could combine with the Informative References.


(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.


N/A.


(13) Have all references within this document been identified as
either normative or informative?


Yes.


(14) Are there normative references to documents that are not ready for
advancement or are otherwise in an unclear state? If such normative
references exist, what is the plan for their completion?


No.


(15) Are there downward normative references references (see RFC 3967)?
If so, list these downward references to support the Area Director in
the Last Call procedure.


No.


(16) Will publication of this document change the status of any
existing RFCs? Are those RFCs listed on the title page header, listed
in the abstract, and discussed in the introduction? If the RFCs are not
listed in the Abstract and Introduction, explain why, and point to the
part of the document where the relationship of this document to the
other RFCs is discussed. If this information is not in the document,
explain why the WG considers it unnecessary.


No.


(17) Describe the Document Shepherd's review of the IANA considerations
section, especially with regard to its consistency with the body of the
document. Confirm that all protocol extensions that the document makes
are associated with the appropriate reservations in IANA registries.
Confirm that any referenced IANA registries have been clearly
identified. Confirm that newly created IANA registries include a
detailed specification of the initial contents for the registry, that
allocations procedures for future registrations are defined, and a
reasonable name for the new registry has been suggested (see RFC 5226).


There are no IANA actions.


(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find
useful in selecting the IANA Experts for these new registries.


N/A.


(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.

N/A.

The following Last Call announcement was sent out:

From: The IESG
To: "IETF-Announce"
CC: wes@mti-systems.com, "Wesley Eddy" , aqm-chairs@ietf.org, ietf@kuehlewind.net, draft-ietf-aqm-pie@ietf.org, aqm@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (PIE: A Lightweight Control Scheme To Address the Bufferbloat Problem) to Experimental RFC


The IESG has received a request from the Active Queue Management and
Packet Scheduling WG (aqm) to consider the following document:
- 'PIE: A Lightweight Control Scheme To Address the Bufferbloat Problem'
  as Experimental RFC

The IESG plans to make a decision in the next few weeks, and solicits
final comments on this action. Please send substantive comments to the
ietf@ietf.org mailing lists by 2016-05-04. Exceptionally, comments may be
sent to iesg@ietf.org instead. In either case, please retain the
beginning of the Subject line to allow automated sorting.

Abstract


  Bufferbloat is a phenomenon where excess buffers in the network cause
  high latency and jitter. As more and more interactive applications
  (e.g. voice over IP, real time video streaming and financial
  transactions) run in the Internet, high latency and jitter degrade
  application performance. There is a pressing need to design
  intelligent queue management schemes that can control latency and
  jitter; and hence provide desirable quality of service to users.

  This document presents a lightweight active queue management design,
  called PIE (Proportional Integral controller Enhanced), that can
  effectively control the average queueing latency to a target value.
  Simulation results, theoretical analysis and Linux testbed results
  have shown that PIE can ensure low latency and achieve high link
  utilization under various congestion situations. The design does not
  require per-packet timestamp, so it incurs very small overhead and is
  simple enough to implement in both hardware and software.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-aqm-pie/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-aqm-pie/ballot/


The following IPR Declarations may be related to this I-D:

  https://datatracker.ietf.org/ipr/2540/
  https://datatracker.ietf.org/ipr/2123/
  https://datatracker.ietf.org/ipr/2187/

As required by RFC 4858, this is the current template for the Document
Shepherd Write-Up.

Changes are expected over time. This version is dated 24 February 2012.

(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)?  Why
is this the proper type of RFC?  Is this type of RFC indicated in the
title page header?


The document is targeted for Experimental.  This was the result of discussion in the working group.  The initial target had been a Proposed Standard, but the level of support for this by the end of the working group process was not high.  There have been good results from studies and deployments so far, and there is no reason to believe this would be harmful to deploy, so the working group believes that greater experimentation with PIE on the Internet should be encouraged, and that it might be a candidate for standardization later.


(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:

Technical Summary

  Relevant content can frequently be found in the abstract
  and/or introduction of the document. If not, this may be
  an indication that there are deficiencies in the abstract
  or introduction.

Abstract:
"""
  Bufferbloat is a phenomenon where excess buffers in the network cause
  high latency and jitter. As more and more interactive applications
  (e.g. voice over IP, real time video streaming and financial
  transactions) run in the Internet, high latency and jitter degrade
  application performance. There is a pressing need to design
  intelligent queue management schemes that can control latency and
  jitter; and hence provide desirable quality of service to users.

  This document presents a lightweight active queue management design,
  called PIE (Proportional Integral controller Enhanced), that can
  effectively control the average queueing latency to a target value.
  Simulation results, theoretical analysis and Linux testbed results
  have shown that PIE can ensure low latency and achieve high link
  utilization under various congestion situations. The design does not
  require per-packet timestamp, so it incurs very small overhead and is
  simple enough to implement in both hardware and software.
"""

Working Group Summary

  Was there anything in WG process that is worth noting? For
  example, was there controversy about particular points or
  were there decisions where the consensus was particularly
  rough?

There were no matters of large controversy, though there have been some criticisms of PIE.  The IPR did not seem to be a blocking point for anyone, but some participants prefered algorithms free of IPR.  There are multiple algorithms that were proposed to the AQM working group, and there are still some developing.  Some aspects of the PIE design were critiqued, and there are some identified matters for future research, but there did not seem to be any disagreement that this is useful to publish at this time.  It is understood that this does not block other algorithms or improvements from happening.  The critical reviews are useful in understanding the differences with other algorithms, and making improvements to PIE while in experimental stage.


Document Quality

  Are there existing implementations of the protocol? Have a
  significant number of vendors indicated their plan to
  implement the specification? Are there any reviewers that
  merit special mention as having done a thorough review,
  e.g., one that resulted in important changes or a
  conclusion that the document had no substantive issues? If
  there was a MIB Doctor, Media Type or other expert review,
  what was its course (briefly)? In the case of a Media Type
  review, on what date was the request posted?


Yes, there are multiple existing implementations, including in simulations, Linux, FreeBSD, and some may be based on description in the DOCSIS specification.  All of the implementation experience was helpful in improving the document quality and clarity when describing the algorithm.  A very thorough technical review was done by Bob Briscoe, and posted as a complete document itself.


Personnel

  Who is the Document Shepherd? Who is the Responsible Area
  Director?

Wesley Eddy (wes@mti-systems.com) is the document shepherd, and Martin Stiemerling (mls.ietf@gmail.com) is the AD.


(3) Briefly describe the review of this document that was performed by
the Document Shepherd.  If this version of the document is not ready
for publication, please explain why the document is being forwarded to
the IESG.


I have reviewed the complete document multiple times.  It is ready for the IESG.


(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?


No concerns.


(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that
took place.


N/A


(6) Describe any specific concerns or issues that the Document Shepherd
has with this document that the Responsible Area Director and/or the
IESG should be aware of? For example, perhaps he or she is uncomfortable
with certain parts of the document, or has concerns whether there really
is a need for it. In any event, if the WG has discussed those issues and
has indicated that it still wishes to advance the document, detail those
concerns here.


No concerns.  Going to Experimental is, it seems, agreeable to the working group.  There might have been concerns (e.g. based on Bob Briscoe's review, or IPR) if targeting Proposed Standard.


(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why.


Yes.  There is IPR disclosed by Cisco, and tracked properly in the IETF system.  The working group has been aware of this.  After WGLC, 2 of the authors explicitly confirmed that all necessary disclosures have been made (the others did not reply).  All authors work for the same company (Cisco).


(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
disclosures.


Yes.  The working group reviewed the IPR disclosure and understands it.


(9) How solid is the WG consensus behind this document? Does it
represent the strong concurrence of a few individuals, with others
being silent, or does the WG as a whole understand and agree with it? 


The consensus seems solid.


(10) Has anyone threatened an appeal or otherwise indicated extreme
discontent? If so, please summarise the areas of conflict in separate
email messages to the Responsible Area Director. (It should be in a
separate email because this questionnaire is publicly available.)


No threats or indications of discontent.


(11) Identify any ID nits the Document Shepherd has found in this
document. (See https://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
thorough.


There are only a couple very small formatting nits that will be fixed by the RFC Editor easily.  The nits reported about references seem to be spurious, and probably result from the use of an "other references" section which the RFC Editor could combine with the Informative References.


(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.


N/A.


(13) Have all references within this document been identified as
either normative or informative?


Yes.


(14) Are there normative references to documents that are not ready for
advancement or are otherwise in an unclear state? If such normative
references exist, what is the plan for their completion?


No.


(15) Are there downward normative references references (see RFC 3967)?
If so, list these downward references to support the Area Director in
the Last Call procedure.


No.


(16) Will publication of this document change the status of any
existing RFCs? Are those RFCs listed on the title page header, listed
in the abstract, and discussed in the introduction? If the RFCs are not
listed in the Abstract and Introduction, explain why, and point to the
part of the document where the relationship of this document to the
other RFCs is discussed. If this information is not in the document,
explain why the WG considers it unnecessary.


No.


(17) Describe the Document Shepherd's review of the IANA considerations
section, especially with regard to its consistency with the body of the
document. Confirm that all protocol extensions that the document makes
are associated with the appropriate reservations in IANA registries.
Confirm that any referenced IANA registries have been clearly
identified. Confirm that newly created IANA registries include a
detailed specification of the initial contents for the registry, that
allocations procedures for future registrations are defined, and a
reasonable name for the new registry has been suggested (see RFC 5226).


There are no IANA actions.


(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find
useful in selecting the IANA Experts for these new registries.


N/A.


(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.

N/A.