Low Latency, Low Loss, and Scalable Throughput (L4S) Internet Service: Architecture
draft-ietf-tsvwg-l4s-arch-20

[Ballot comment]
** Section 6.4.2.  (Per the telechat conversation, move to COMMENT) My read of Figure 3 is that the suggested architecture can be incrementally deployed.  My other read is that it appears that this staged deployment isn’t safe outside of controlled environments (i.e., for the Internet) until after phase 1.  Assuming this is accurate, please add clear normative language that partial roll-outs of the L4S architecture MUST NOT occur outside of controlled environment until .

** Section 8.1.
  In the current Internet, scheduling usually enforces separation
  between 'sites'

If would be clearer to explain scheduling of what and by whom.

** Section 8.1

  However, there has
  never been a universal need to police the rate of individual
  application flows - the Internet has generally always relied on self-
  restraint of congestion controls at senders for sharing intra-'site'
  capacity.

I don’t follow the generalization being suggested here.  Is the text suggesting that enterprises do not shape traffic on a per application basis?  “Upstream networks” to provide different treatment of select traffic?  Is there a measurement study that can be cited?

** Section 8.1.  The first paragraph ends with a conclusion that there isn’t a universal need to police individual flow rates.  However, the second paragraph then discusses the use of per-flow-queuing.  One paragraph doesn’t follow from the other.  If no one does per-flow treatment as suggested, why discuss the approach?

** Section 8.2

  It is hoped that self-interest and guidance on dynamic
  behaviour (especially flow start-up, which might need to be
  standardized) will be sufficient to prevent transports from sending
  excessive bursts of L4S traffic, given the application's own latency
  will suffer most from such behaviour.

Why is “self-interest and guidance on dynamic behaviour” the appropriate threat model?

** Section 8.2

None of these possible queue protection capabilities are considered a
  necessary part of the L4S architecture, which works without them

Could this be restated.  The current text suggests to me that various security mitigations are not part of the L4S architecture.  I don’t see how this would be possible if it were to see Internet deployment.

** Section 8.3

  So, in networks that already use rate policers and plan to deploy
  L4S, it will be preferable to redesign these rate policers to be more
  friendly to the L4S service.

It might be helpful to be more specific on where this traffic shaping is happening as part of the migration consideration.

** Section 8.4.  This section discusses malicious senders, thank you.  Could a statement also be made about an on-path attacker modifying the ECN marks in the absence of integrity mechanisms.  For example, draft-ietf-tsvwg-l4s-ids notes in Section 5.4.1.1:

  If a non-compliant or
  malicious network node did swap ECT(0) to ECT(1), the packet could
  subsequently be ECN-marked by a downstream L4S AQM, but the sender
  would respond to congestion indications thinking it had sent a
  Classic packet.  This could result in the flow yielding excessively
  to other L4S flows sharing the downstream bottleneck.

** Section 8.5.
  Because L4S can provide low delay for a broad set of applications
  that choose to use it, there is no need for individual applications
  or classes within that broad set to be distinguishable in any way
  while traversing networks. 

From a purely technical view, this might be true.  However, couldn’t local policy require different treatment?

** Section 8.5.
  There may be some types of traffic
  that prefer not to use L4S, but the coarse binary categorization of
  traffic reveals very little that could be exploited to compromise
  privacy.

After L4S is more widely adopted, that specific application could be identified by their _lack_ use of L4S?  In the early days where there is limited L4S use, wouldn’t these early adopter stick out? 

Nits
** Section 2.  Typo. s/two queues is sufficient/two queues are sufficient/

** Section 5.1.  Per “Cubic [RFC8312] was developed to be less unscalable …”, if there a way to rephrase “less unscalable”?

** Section 6.4.1.  Per

An L4S AQM would often next be needed where the WiFi links in a home
  sometimes become the bottleneck. 
Is this suggesting that L4S AQM isn’t suitable for WiFi links but that is future work?

** Section 4.6.2.  s/Scalable CC/scalable congestion control approach/

[Ballot comment]
Hi,

Thanks for the spec.  This is outside of my area of expertise, and I've been time constrained this week, but I found this document to be pretty easy to read and certainly the technology sounds interesting and potentially very useful so that you for your work on this.

I guess that my only criticism, and it is not easily/readably actionable, is that some of the sections felt a little bit repetitive from early parts in the document, and perhaps earlier parts of the document could possible benefit from being shortened or made more concise.  One obvious change that has already been suggested by others, getting the abstract down to a single paragraph summary would probably be a fairly easy improvement.  Other than that, I don't really have any other actionable suggestions, sorry.

This paragraph:

      To enable L4S, the standards track Classic ECN spec. [RFC3168]
      has had to be updated to allow L4S packets to depart from the
      'equivalent to drop' constraint.  [RFC8311] is a standards track
      update to relax specific requirements in RFC 3168 (and certain
      other standards track RFCs), which clears the way for the
      experimental changes proposed for L4S.  [RFC8311] also
      reclassifies the original experimental assignment of the ECT(1)
      codepoint as an ECN nonce [RFC3540] as historic.

also stood out as being useful whilst the document was being developed, but perhaps less useful in a published RFC, and hence I did wonder whether this paragraph could be elided or shortened.

Regards,
Rob

[Ballot comment]
# Security AD comments for {draft-ietf-tsvwg-l4s-arch-19}
CC @paulwouters

This is somewhat out of my area of expertise, but upon reading it, it seems sensible to me. Just a few minor comments that can be taken into account or ignored.

## Comments

### Abstract

This is very very long. Perhaps some can be moved to the Introduction or cut? For example (but not having given it enough thought to actually use this): "This document describes the architecture for the "Low Latency, Low Loss, Scalable Throughput" (L4S) protocol to archive lower latency traffic on the internet. It describes its design decisions to make it work via incremental deployment on the internet and in a worst case won't perform worse than currently deployed latency minimizing techniques."

### Security Considerations

  However, there has
  never been a universal need to police the rate of individual
  application flows - the Internet has generally always relied on self-
  restraint of congestion controls

The first voip clients on the internet in the 90s would blast UDP as fast as possible. ISPs started filtering it. I wouldn't call that self-restraint, but one might argue that they were forced to do so to remain in operation, so perhaps it qualifies a self-restraint :P

  Whether burst policing becomes necessary remains to be seen.  Without
  it, there will be potential for attacks on the low latency of the L4S
  service.

If something can be abused to gain an advantage, it will be. So in that sense burst policing seems inevitable. But I can see how routers near the user could punish abusers to go into a slower queue and this section links to examples for that. So L4S won't really change this. Similarly, it can be used to create a two-tier internet ("premium users") but here too this can already be done without L4S.

[Ballot comment]

# Éric Vyncke, INT AD, comments for draft-ietf-tsvwg-l4s-arch-19
CC @evyncke

Thank you for the work put into this document. Please note that I am far from being an expert on transport issues... so I am afraid that my review is not deep and may have missed obvious points.

I especially like the incremental deployment approach.

Please find below some non-blocking COMMENT points (but replies would be appreciated even if only for my own education), and some nits.

Special thanks to Wesley Eddy for the shepherd's detailed write-up *including* the rough (?) WG consensus *and* the justification of the intended status.

Please note that Benno Overeinder is the Internet directorate reviewer (at my request) and you may want to consider this int-dir reviews as well when Benno will complete the review (no need to wait for it though):
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-l4s-arch/reviewrequest/16167/

I hope that this review helps to improve the document,

Regards,

-éric

## COMMENTS

### id-nits and obsolete references

[id-nits] (https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-tsvwg-l4s-arch-19.txt) indicates two references to obsolete RFC (4960 and 7540). Probably worth updating the references.

### Multicast ?

While the answer seems obvious, should there be a mention that L4S technique only applies to unicast traffic ?

###


### Very long abstract...

This is probably the longest abstract for the last couple of months ;-)

No need to reply or change the document, but the abstract also somehow smells like a marketing text...

### Section 1, on purpose ?

```
  ... Queuing in access
  network bottlenecks is typically configured to cause overall network
  delay to roughly double during a long-running flow, relative to
  expected base (unloaded) path delay [BufferSize].
```

Is this really configured so on purpose ? Probably not, even if the above text seems to indicate that this is on purpose.

### Section 1, TCP only ?

The following text seems to indicate that TCP is the major transport protocol, but (see caveat about my lack of transport expertise) it seems to me that QUIC (and plain UDP) are becoming more important:
```
  The root of the problem is the presence of standard TCP congestion
  control (Reno [RFC5681]) or compatible variants (e.g. TCP
  Cubic [RFC8312]).
```
I.e., if similar mechanisms exist in QUIC, then it is worth mentioning.

### Section 2, incremental deployment ?

```
  ... Because ECN support is
  essential for L4S, senders use the ECN field as the protocol that
  allows the network to identify which packets are L4S and which are
  Classic.
```
seems to contradict the 'incremental deployment' statement as the network needs to be able to differentiate traffic. Or did I miss something ?

### Section 2, which part of the host ?

```
      ... A host needs to distinguish L4S and Classic packets
      with an identifier so that the network can classify them into
      their separate treatments. ...
```
I would assume that a host stack as a local API so that applications can signal L4S vs. classic traffic.

Also, it is unclear (to me) whether it is the sending part of the host or the receiving part ?

Finally, with some transport services (e.g., QUIC) moving to the user space, is the above statement still applicable ?

### Section 4.1

Unsure how `unassignment of an identifier` relates to item a) below.

### Section 6.1

Again, please bear with my lack of knowledge, but I wonder what is the 'load' in the text below. Is the 'load' only interactive traffic (then I wonder how there could be no congestion) or is it a mix with non-interactive traffic (the proverbial SW upgrade, which can be delayed):
```
  With the L4S approach, the following existing applications also
  experience significantly better quality of experience under load:
```

### Section 6.3

This section could probably be extended as Wi-Fi & satellite links have properties going beyond latency (e.g., packet loss).

For a non native English reader, the use of 'pole' is really hard to parse.

### Section 8.1 and others

I wonder whether this section belongs to security considerations or rather to deployment considerations.

### Section 8.4

The text does not convince me that ECN can be trusted (i.e., the network provides ECN integrity). Should there simply be some text about 'best effort' ?

### Privacy considerations

Does the use of visible ECN marking leak some information about its (potentially encrypted) content ?

## NITS

### E.g. comma

AFAIK, all 'e.g.' must be followed by a comma.

### Spec

Suggest to use 'specification' rather than 'spec' ;-)

## Notes

This review is in the ["IETF Comments" Markdown format][ICMF], You can use the
[`ietf-comments` tool][ICT] to automatically convert this review into
individual GitHub issues.

[ICMF]: https://github.com/mnot/ietf-comments/blob/main/format.md
[ICT]: https://github.com/mnot/ietf-comments


*************
As noted in https://www.ietf.org/blog/handling-iesg-ballot-positions/, a
DISCUSS ballot is a request to have a discussion; I really think that the
document would be improved with a change here, but can be convinced otherwise.

[Ballot discuss]
** Section 6.4.2.  My read of Figure 3 is that the suggested architecture can be incrementally deployed.  My other read is that it appears that this staged deployment isn’t safe outside of controlled environments (i.e., for the Internet) until after phase 1.  Assuming this is accurate, please add clear normative language that partial roll-outs of the L4S architecture MUST NOT occur outside of controlled environment until .

[Ballot comment]
** Section 8.1.
  In the current Internet, scheduling usually enforces separation
  between 'sites'

If would be clearer to explain scheduling of what and by whom.

** Section 8.1

  However, there has
  never been a universal need to police the rate of individual
  application flows - the Internet has generally always relied on self-
  restraint of congestion controls at senders for sharing intra-'site'
  capacity.

I don’t follow the generalization being suggested here.  Is the text suggesting that enterprises do not shape traffic on a per application basis?  “Upstream networks” to provide different treatment of select traffic?  Is there a measurement study that can be cited?

** Section 8.1.  The first paragraph ends with a conclusion that there isn’t a universal need to police individual flow rates.  However, the second paragraph then discusses the use of per-flow-queuing.  One paragraph doesn’t follow from the other.  If no one does per-flow treatment as suggested, why discuss the approach?

** Section 8.2

  It is hoped that self-interest and guidance on dynamic
  behaviour (especially flow start-up, which might need to be
  standardized) will be sufficient to prevent transports from sending
  excessive bursts of L4S traffic, given the application's own latency
  will suffer most from such behaviour.

Why is “self-interest and guidance on dynamic behaviour” the appropriate threat model?

** Section 8.2

None of these possible queue protection capabilities are considered a
  necessary part of the L4S architecture, which works without them

Could this be restated.  The current text suggests to me that various security mitigations are not part of the L4S architecture.  I don’t see how this would be possible if it were to see Internet deployment.

** Section 8.3

  So, in networks that already use rate policers and plan to deploy
  L4S, it will be preferable to redesign these rate policers to be more
  friendly to the L4S service.

It might be helpful to be more specific on where this traffic shaping is happening as part of the migration consideration.

** Section 8.4.  This section discusses malicious senders, thank you.  Could a statement also be made about an on-path attacker modifying the ECN marks in the absence of integrity mechanisms.  For example, draft-ietf-tsvwg-l4s-ids notes in Section 5.4.1.1:

  If a non-compliant or
  malicious network node did swap ECT(0) to ECT(1), the packet could
  subsequently be ECN-marked by a downstream L4S AQM, but the sender
  would respond to congestion indications thinking it had sent a
  Classic packet.  This could result in the flow yielding excessively
  to other L4S flows sharing the downstream bottleneck.

** Section 8.5.
  Because L4S can provide low delay for a broad set of applications
  that choose to use it, there is no need for individual applications
  or classes within that broad set to be distinguishable in any way
  while traversing networks. 

From a purely technical view, this might be true.  However, couldn’t local policy require different treatment?

** Section 8.5.
  There may be some types of traffic
  that prefer not to use L4S, but the coarse binary categorization of
  traffic reveals very little that could be exploited to compromise
  privacy.

After L4S is more widely adopted, that specific application could be identified by their _lack_ use of L4S?  In the early days where there is limited L4S use, wouldn’t these early adopter stick out? 

Nits
** Section 2.  Typo. s/two queues is sufficient/two queues are sufficient/

** Section 5.1.  Per “Cubic [RFC8312] was developed to be less unscalable …”, if there a way to rephrase “less unscalable”?

** Section 6.4.1.  Per

An L4S AQM would often next be needed where the WiFi links in a home
  sometimes become the bottleneck. 
Is this suggesting that L4S AQM isn’t suitable for WiFi links but that is future work?

** Section 4.6.2.  s/Scalable CC/scalable congestion control approach/

[Ballot comment]
# GEN AD review of draft-ietf-tsvwg-l4s-arch-19

CC @larseggert

## Comments

### "Abstract", paragraph 0
```
  Abstract
```
Does the abstract really need to be this long?

### Section 3, paragraph 1
```
    Note: The following definitions are copied from the L4S ECN
    spec [I-D.ietf-tsvwg-ecn-l4s-id] for convenience.  If there are
    accidental differences, those in [I-D.ietf-tsvwg-ecn-l4s-id] take
    precedence.
```
Please instruct the RFC Editor to copy in the definitions from
[I-D.ietf-tsvwg-ecn-l4s-id] during production and to remove the note above.

## Nits

All comments below are about very minor potential issues that you may choose to
address in some way - or ignore - as you see fit. Some were flagged by
automated tools (via https://github.com/larseggert/ietf-reviewtool), so there
will likely be some false positives. There is no need to let me know what you
did with these suggestions.

### Outdated references

Reference `[RFC7540]` to `RFC7540`, which was obsoleted by `RFC9113` (this may
be on purpose).

Reference `[RFC4960]` to `RFC4960`, which was obsoleted by `RFC9260` (this may
be on purpose).

### URLs

These URLs in the document did not return content:

* https://www.bell-labs.com/usr/koen.de_schepper

These URLs in the document can probably be converted to HTTPS:

* http://doi.acm.org/10.1145/2663716.2663730
* http://www.cablelabs.com/wp-content/uploads/2013/11/Active_Queue_Management_Algorithms_DOCSIS_3_0.pdf
* http://bobbriscoe.net/
* http://dl.acm.org/citation.cfm?doid=2910017.2910633
* http://ee.lbl.gov/papers/congavoid.pdf
* http://www.it.uc3m.es

### Grammar/style

#### Section 1, paragraph 8
```
architecture is, rather than why. Finally Section 5 justifies why each eleme
                                  ^^^^^^^
```
A comma may be missing after the conjunctive/linking adverb "Finally".

#### Section 1.1, paragraph 1
```
he document ends with the usual tail pieces, including extensive discussion
                                ^^^^^^^^^^^
```
The word "tailpieces" is spelled as one word.

#### Section 2, paragraph 2
```
es in Section 5.1 and [RFC3649]. Therefore control of queuing and utilizatio
                                ^^^^^^^^^
```
A comma may be missing after the conjunctive/linking adverb "Therefore".

#### Section 3, paragraph 4
```
(e.g. DNS, VoIP, game sync datagrams, etc). Reno-friendly: The subset of Clas
                                      ^^^
```
A period is needed after the abbreviation "etc.".

#### Section 3, paragraph 9
```
ueue protection in this document. Otherwise the term rate policing is used.
                                  ^^^^^^^^^
```
A comma may be missing after the conjunctive/linking adverb "Otherwise".

#### Section 4.2, paragraph 8
```
o ECT(1) packets [FQ_CoDel_Thresh]. Then if there is a flow of non-ECN or ECT
                                    ^^^^
```
Consider adding a comma here.

#### Section 4.2, paragraph 11
```
equalize flow-rates (perhaps in a similar way to Approx Fair CoDel [AFCD],
                              ^^^^^^^^^^^^^^^^
```
Consider replacing this phrase with the adverb "similarly" to avoid wordiness.

#### Section 4.2, paragraph 13
```
nd QUIC transports, amongst others. Also an L4S variant of the RMCAT SCReAM c
                                    ^^^^
```
A comma may be missing after the conjunctive/linking adverb "Also".

#### Section 4.3, paragraph 2
```
more explicit signals can be applied so the queue can be kept short whatever
                                    ^^^
```
Use a comma before "so" if it connects two independent clauses (unless they are
closely connected and short).

#### Section 4.3, paragraph 3
```
doesn't know the round trip times of any of the flows. So if the network is
                                  ^^^^^^^^^
```
Consider simply using "of" instead.

#### Section 4.3, paragraph 3
```
e Classic approach), it has to assume a worst case RTT, otherwise long RTT fl
                                      ^
```
Use "the" before the superlative.

#### Section 5.1, paragraph 5
```
s the recovery time is 24.3 s. In contrast a scalable congestion control like
                                  ^^^^^^^^
```
A comma may be missing after the conjunctive/linking adverb "contrast".

#### Section 5.2, paragraph 6
```
ll treats ECN and drop the same. Therefore ABE exploits any lower queuing de
                                ^^^^^^^^^
```
A comma may be missing after the conjunctive/linking adverb "Therefore".

#### Section 5.2, paragraph 6
```
rt-up phase. L4S complements BBR. Indeed BBRv2 can use L4S ECN where availab
                                  ^^^^^^
```
A comma may be missing after the conjunctive/linking adverb "Indeed".

#### Section 5.2, paragraph 11
```
displayed a viewport taken from a 360 degree camera in a racing car. The user
                                  ^^^^^^^^^^
```
When "360-degree" is used as a modifier, it is usually spelled with a hyphen.

#### Section 5.2, paragraph 17
```
packets while building each burst. WiFi, PON and cable all involve such pack
                                    ^^^^
```
Did you mean "Wi-Fi"? (This is the officially approved term by the Wi-Fi
Alliance.).

#### Section 6.1, paragraph 1
```
ifically: * Radio links (cellular, WiFi, satellite) that are distant from th
                                  ^^^^
```
Did you mean "Wi-Fi"? (This is the officially approved term by the Wi-Fi
Alliance.).

#### Section 6.2, paragraph 12
```
ould often next be needed where the WiFi links in a home sometimes become th
                                    ^^^^
```
Did you mean "Wi-Fi"? (This is the officially approved term by the Wi-Fi
Alliance.).

#### Section 6.4.1, paragraph 6
```
stream bottlenecks in one go ---whether or not all the origin servers were up
                                ^^^^^^^^^^^^^^
```
Consider shortening this phrase to just "whether". It is correct though if you
mean "regardless of whether".

#### Section 6.4.2, paragraph 1
```
ll clients that support AccECN (whether or not they support L4S as well). And
                                ^^^^^^^^^^^^^^
```
Consider shortening this phrase to just "whether". It is correct though if you
mean "regardless of whether".

#### Section 6.4.2, paragraph 14
```
how operators can use an additional local classifiers (see section 5.4 of th
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
The plural noun "classifiers" cannot be used with the article "an". Did you
mean "an additional local classifier" or "additional local classifiers"?

#### Section 6.4.3, paragraph 8
```
yments of new bursty malware, in a similar way to how traffic from flooding
                              ^^^^^^^^^^^^^^^^
```
Consider replacing this phrase with the adverb "similarly" to avoid wordiness.

#### Section 6.4.4, paragraph 1
```
distributed across a subnet inter-communicating using lower layer control me
                            ^^^^^^^^^^^^^^^^^^^
```
This word is normally spelled as one.

#### Section 8.1, paragraph 1
```
re, which works without them (in a similar way to how the Internet works wit
                              ^^^^^^^^^^^^^^^^
```
Consider replacing this phrase with the adverb "similarly" to avoid wordiness.

#### Section 8.2, paragraph 7
```
TCP BBR v2 Alpha/Preview Release", github repository; Linux congestion contr
                                  ^^^^^^
```
The official name of this software platform is spelled GitHub.

#### Section 9, paragraph 7
```
net: Understanding and Solutions", Masters Thesis; Karlstad Uni, Dept of Math
                                  ^^^^^^^
```
For an academic degree, use "Master's".

#### Section 9, paragraph 28
```
[SCReAM] Johansson, I., "SCReAM", github repository; , <https://github.com/Er
                                  ^^^^^^
```
The official name of this software platform is spelled GitHub.

#### Section 9, paragraph 29
```
ng for 4G in a network simulator", Masters Thesis, Uni Oslo , June 2019. Ack
                                  ^^^^^^^
```
For an academic degree, use "Master's".

## Notes

This review is in the ["IETF Comments" Markdown format][ICMF], You can use the
[`ietf-comments` tool][ICT] to automatically convert this review into
individual GitHub issues. Review generated by the [`ietf-reviewtool`][IRT].

[ICMF]: https://github.com/mnot/ietf-comments/blob/main/format.md
[ICT]: https://github.com/mnot/ietf-comments
[IRT]: https://github.com/larseggert/ietf-reviewtool

[Ballot comment]
# Internet AD comments for {draft-ietf-tsvwg-l4s-arch-19}
CC @ekline

## Comments

### S6.1

* Are there any handy, good references for human visual perception/tolerance
  of delay?

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

The IANA Functions Operator has reviewed draft-ietf-tsvwg-l4s-arch-18, which is currently in Last Call, and has the following comments:

We understand that this document doesn't require any registry 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, we do not object.

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

For definitions of IANA review states, please see:

https://datatracker.ietf.org/help/state/draft/iana-review

Thank you,

Michelle Thangtamsatid
IANA Services Specialist

The following Last Call announcement was sent out (ends 2022-07-21):

From: The IESG
To: IETF-Announce
CC: Wesley Eddy , draft-ietf-tsvwg-l4s-arch@ietf.org, martin.h.duke@gmail.com, tsvwg-chairs@ietf.org, tsvwg@ietf.org, wes@mti-systems.com
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (Low Latency, Low Loss, Scalable Throughput (L4S) Internet Service: Architecture) to Informational RFC


The IESG has received a request from the Transport Area Working Group WG
(tsvwg) to consider the following document: - 'Low Latency, Low Loss,
Scalable Throughput (L4S) Internet Service:
  Architecture'
  as Informational 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
last-call@ietf.org mailing lists by 2022-07-21. 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


  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-l4s-arch/



No IPR declarations have been submitted directly on this I-D.

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 1 November 2019.

(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?

Informational.  This is indicated properly and is the proper type of RFC since this describes the architecture for L4S, while other Experimental RFCs describe the transport behaviors for use of the L4S identifier and DualQ that is one of the possible queueing options compatible with this architecture.

(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: (from abstract)

  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.

Working Group Summary:

The working group largely supports and is enthusiastic about L4S technology, which this document is a part of.  It was last called along with 2 other L4S documents.  There is a wider than normal level of support that has been expressed for this work, but it is not unanimous.  There are also some WG participants who have concerns about L4S or prefer an alternative approach.  The working group had many long email threads and conducted several interim meetings focused on L4S, its goals, technical challenges, and concerns with the approach and potential impact on Internet safety.  Full agreement was not obtained in all cases, but significant work was done to address the issues that were agreed upon, and each concern was considered in detail by the working group, even if some resolutions were not unanimously agreed with.

Document Quality:

There are multiple existing implementations of the technology described, and around 25 vendors and operators have indicated intentions to experiment with the overall L4S technology.

Personnel:

Wesley Eddy is the document shepherd and Martin Duke is the responsible 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 document myself, and believe it is ready for publication.  In addition, both other TSVWG co-chairs have closely reviewed and commented on earlier revisions of the document.

(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.

Since the document deals with transport, congestion control, packet marking, and queuing behavior, there can be security, operations, internet, and routing area interests.  There has been a healthy mix of academic, industry/vendor, and operator participation in this work, and a breadth of reviews have been incorporated.

(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.

There are no personal concerns of my own.  However, there have been concerns raised in the working group, discussed in question 9 below.

(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.

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

No.

(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?

There was a combined last call for this and the other two main L4S documents.  During that last call, it was clear that while a majority strongly supports the work and is eager to experiment with the technology, there are still also a number of participants who have concerns and/or prefer alternatives to L4S.  The working group devoted considerable time, including multiple focused interim meetings in order to understand objections and try to address or mitigate all concerns.  It is clear that while there are still some technical disagreements, there is a great deal of support and even wider than normal support for going forward with this work; spanning industry, including vendors, network operators, and congestion control researchers.

There were very specific technical concerns and disagreements with the other 2 L4S drafts (on the ECN usage and DualQ).  Specific concerns related to the content of those drafts are discussed in their writeups.
- In this particular document there were some early objections related to use of the term "classic" for traditional non-L4S transports and queues, though no superior term was able to be agreed on, and only a small number of people seemed unhappy with "classic".
- More substantially, there were concerns raised about the overall state of development and study of the combined L4S architecture elements, particularly the compliant transport protocols.  The TCP Prague reference code had some issues discovered (and fixed), and some of the working group participants did not feel like it was mature enough nor were the results of tests encouraging enough for them to support L4S advancing.  Note that other L4S transports beyond just TCP Prague have been under development by other groups, who reviewed the L4S drafts and reported on their capabilities to meet L4S requirements with their transports.
- The selection of the L4S identifier (in the companion ecn-l4s-id document) is not specific to this architecture draft, but is at the root of a great deal of the lack of unanimous support.  Since the beginning of this work, it was well understood that enhancing ECN involves tradeoffs in the choice of header encodings selected, since there are limited options in terms of the header bits, codepoints, and other fields like DSCP that can be leveraged.  The working group went through a process of assessing the pros and cons of all of the options that were put on the table.  The different weights that participants attach to the importance of these tradeoffs seems to be a major source of the inability to unanimously agree on the particular L4S usage of ECT1 (and CE).  It was remarked in one WG meeting that we ideally would have 5 codepoints, but unfortunately need to live with 4 and engineer within that.  As a possible supplement for the limited ECN codepoints, the working group considered pros and cons of different means of using DSCP values, multiple times over the life of these documents.  Some participants preferred approaches relying on DSCP, based on their view of the tradeoffs.
- Some of the objecting participants have proposed another technology (SCE) to enhance ECN differently, and incompatibly with L4S and this architecture.  After careful consideration and a focused interim, the working group strongly supported the use of ECT(1) as an input to classification as in L4S to enable low latency traffic identification.  SCE proponents propose that their alternative approach also can control latency, but make use of ECT(1) as an output to indicate finer-grained levels of congestion.

One potential mitigation for some of these concerns is that the TSVWG plans to be an open forum for experimenters to continue to present data and other findings, where the WG can ask questions, explore whether specific concerns have manifested, and discuss potential further development and advancement of L4S along the Standards Track.

(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.)

Some participants may feel strongly enough against L4S to consider an appeal.

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

There are very minor ID nits that can be corrected during publication.  These are the instances reported of non-ASCII characters and the outdated references to the other L4S documents.

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

N/A.

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

Yes - all are informative.

(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 (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.

N/A.

(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 8126).

There are (correctly) no IANA considerations.

(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, YANG modules, etc.

N/A  - there are no formal languages used.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?

N/A.

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 1 November 2019.

(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?

Informational.  This is indicated properly and is the proper type of RFC since this describes the architecture for L4S, while other Experimental RFCs describe the transport behaviors for use of the L4S identifier and DualQ that is one of the possible queueing options compatible with this architecture.

(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: (from abstract)

  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.

Working Group Summary:

The working group largely supports and is enthusiastic about L4S technology, which this document is a part of.  It was last called along with 2 other L4S documents.  There is a wider than normal level of support that has been expressed for this work, but it is not unanimous.  There are also some WG participants who have concerns about L4S or prefer an alternative approach.  The working group had many long email threads and conducted several interim meetings focused on L4S, its goals, technical challenges, and concerns with the approach and potential impact on Internet safety.  Full agreement was not obtained in all cases, but significant work was done to address the issues that were agreed upon, and each concern was considered in detail by the working group, even if some resolutions were not unanimously agreed with.

Document Quality:

There are multiple existing implementations of the technology described, and around 25 vendors and operators have indicated intentions to experiment with the overall L4S technology.

Personnel:

Wesley Eddy is the document shepherd and Martin Duke is the responsible 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 document myself, and believe it is ready for publication.  In addition, both other TSVWG co-chairs have closely reviewed and commented on earlier revisions of the document.

(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.

Since the document deals with transport, congestion control, packet marking, and queuing behavior, there can be security, operations, internet, and routing area interests.  There has been a healthy mix of academic, industry/vendor, and operator participation in this work, and a breadth of reviews have been incorporated.

(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.

There are no personal concerns of my own.  However, there have been concerns raised in the working group, discussed in question 9 below.

(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.

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

No.

(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?

There was a combined last call for this and the other two main L4S documents.  During that last call, it was clear that while a majority strongly supports the work and is eager to experiment with the technology, there are still also a number of participants who have concerns and/or prefer alternatives to L4S.  The working group devoted considerable time, including multiple focused interim meetings in order to understand objections and try to address or mitigate all concerns.  It is clear that while there are still some technical disagreements, there is a great deal of support and even wider than normal support for going forward with this work; spanning industry, including vendors, network operators, and congestion control researchers.

There were very specific technical concerns and disagreements with the other 2 L4S drafts (on the ECN usage and DualQ).  Specific concerns related to the content of those drafts are discussed in their writeups.
- In this particular document there were some early objections related to use of the term "classic" for traditional non-L4S transports and queues, though no superior term was able to be agreed on, and only a small number of people seemed unhappy with "classic".
- More substantially, there were concerns raised about the overall state of development and study of the combined L4S architecture elements, particularly the compliant transport protocols.  The TCP Prague reference code had some issues discovered (and fixed), and some of the working group participants did not feel like it was mature enough nor were the results of tests encouraging enough for them to support L4S advancing.  Note that other L4S transports beyond just TCP Prague have been under development by other groups, who reviewed the L4S drafts and reported on their capabilities to meet L4S requirements with their transports.
- The selection of the L4S identifier (in the companion ecn-l4s-id document) is not specific to this architecture draft, but is at the root of a great deal of the lack of unanimous support.  Since the beginning of this work, it was well understood that enhancing ECN involves tradeoffs in the choice of header encodings selected, since there are limited options in terms of the header bits, codepoints, and other fields like DSCP that can be leveraged.  The working group went through a process of assessing the pros and cons of all of the options that were put on the table.  The different weights that participants attach to the importance of these tradeoffs seems to be a major source of the inability to unanimously agree on the particular L4S usage of ECT1 (and CE).  It was remarked in one WG meeting that we ideally would have 5 codepoints, but unfortunately need to live with 4 and engineer within that.  As a possible supplement for the limited ECN codepoints, the working group considered pros and cons of different means of using DSCP values, multiple times over the life of these documents.  Some participants preferred approaches relying on DSCP, based on their view of the tradeoffs.
- Some of the objecting participants have proposed another technology (SCE) to enhance ECN differently, and incompatibly with L4S and this architecture.  After careful consideration and a focused interim, the working group strongly supported the use of ECT(1) as an input to classification as in L4S to enable low latency traffic identification.  SCE proponents propose that their alternative approach also can control latency, but make use of ECT(1) as an output to indicate finer-grained levels of congestion.

One potential mitigation for some of these concerns is that the TSVWG plans to be an open forum for experimenters to continue to present data and other findings, where the WG can ask questions, explore whether specific concerns have manifested, and discuss potential further development and advancement of L4S along the Standards Track.

(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.)

Some participants may feel strongly enough against L4S to consider an appeal.

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

There are very minor ID nits that can be corrected during publication.  These are the instances reported of non-ASCII characters and the outdated references to the other L4S documents.

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

N/A.

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

Yes - all are informative.

(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 (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.

N/A.

(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 8126).

There are (correctly) no IANA considerations.

(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, YANG modules, etc.

N/A  - there are no formal languages used.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?

N/A.

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 1 November 2019.

(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?

Informational.  This is indicated properly and is the proper type of RFC since this describes the architecture for L4S, while other Experimental RFCs describe the transport behaviors for use of the L4S identifier and DualQ that is one of the possible queueing options compatible with this architecture.

(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: (from abstract)

  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.

Working Group Summary:

The working group largely supports and is enthusiastic about L4S technology, which this document is a part of.  It was last called along with 2 other L4S documents.  There is a wider than normal level of support that has been expressed for this work, but it is not unanimous.  There are also some WG participants who have concerns about L4S or prefer an alternative approach.  The working group had many long email threads and conducted several interim meetings focused on L4S, its goals, technical challenges, and concerns with the approach and potential impact on Internet safety.  Full agreement was not obtained in all cases, but significant work was done to address the issues that were agreed upon, and each concern was considered in detail by the working group, even if some resolutions were not unanimously agreed with.

Document Quality:

There are multiple existing implementations of the technology described, and around 25 vendors and operators have indicated intentions to experiment with the overall L4S technology.

Personnel:

Wesley Eddy is the document shepherd and Martin Duke is the responsible 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 document myself, and believe it is ready for publication.  In addition, both other TSVWG co-chairs have closely reviewed and commented on earlier revisions of the document.

(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.

Since the document deals with transport, congestion control, packet marking, and queuing behavior, there can be security, operations, internet, and routing area interests.  There has been a healthy mix of academic, industry/vendor, and operator participation in this work, and a breadth of reviews have been incorporated.

(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.

There are no personal concerns of my own.  However, there have been concerns raised in the working group, discussed in question 9 below.

(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.

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

No.

(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?

There was a combined last call for this and the other two main L4S documents.  During that last call, it was clear that while a majority strongly supports the work and is eager to experiment with the technology, there are still also a number of participants who have concerns and/or prefer alternatives to L4S.  The working group devoted considerable time, including multiple focused interim meetings in order to understand objections and try to address or mitigate all concerns.  It is clear that while there are still some technical disagreements, there is a great deal of support and even wider than normal support for going forward with this work; spanning industry, including vendors, network operators, and congestion control researchers.

There were very specific technical concerns and disagreements with the other 2 L4S drafts (on the ECN usage and DualQ).  Specific concerns related to the content of those drafts are discussed in their writeups.
- In this particular document there were some early objections related to use of the term "classic" for traditional non-L4S transports and queues, though no superior term was able to be agreed on, and only a small number of people seemed unhappy with "classic".
- More substantially, there were concerns raised about the overall state of development and study of the combined L4S architecture elements, particularly the compliant transport protocols.  The TCP Prague reference code had some issues discovered (and fixed), and some of the working group participants did not feel like it was mature enough nor were the results of tests encouraging enough for them to support L4S advancing.  Note that other L4S transports beyond just TCP Prague have been under development by other groups, who reviewed the L4S drafts and reported on their capabilities to meet L4S requirements with their transports.
- The selection of the L4S identifier (in the companion ecn-l4s-id document) is not specific to this architecture draft, but is at the root of a great deal of the lack of unanimous support.  Since the beginning of this work, it was well understood that enhancing ECN involves tradeoffs in the choice of header encodings selected, since there are limited options in terms of the header bits, codepoints, and other fields like DSCP that can be leveraged.  The working group went through a process of assessing the pros and cons of all of the options that were put on the table.  The different weights that participants attach to the importance of these tradeoffs seems to be a major source of the inability to unanimously agree on the particular L4S usage of ECT1 (and CE).  It was remarked in one WG meeting that we ideally would have 5 codepoints, but unfortunately need to live with 4 and engineer within that.  As a possible supplement for the limited ECN codepoints, the working group considered pros and cons of different means of using DSCP values, multiple times over the life of these documents.  Some participants preferred approaches relying on DSCP, based on their view of the tradeoffs.
- Some of the objecting participants have proposed another technology (SCE) to enhance ECN differently, and incompatibly with L4S and this architecture.  After careful consideration and a focused interim, the working group strongly supported the use of ECT(1) as an input to classification as in L4S to enable low latency traffic identification.  SCE proponents believe their alternative approach also can control latency, but use ECT(1) as an output to indicate finer-grained levels of congestion.

One potential mitigation for some of these concerns is that the TSVWG plans to be an open forum for experimenters to continue to present data and other findings, where the WG can ask questions, explore whether specific concerns have manifested, and discuss potential further development and advancement of L4S along the Standards Track.

(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.)

Some participants may feel strongly enough against L4S to consider an appeal.

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

There are very minor ID nits that can be corrected during publication.  These are the instances reported of non-ASCII characters and the outdated references to the other L4S documents.

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

N/A.

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

Yes - all are informative.

(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 (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.

N/A.

(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 8126).

There are (correctly) no IANA considerations.

(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, YANG modules, etc.

N/A  - there are no formal languages used.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?

N/A.

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 1 November 2019.

(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?

Informational.  This is indicated properly and is the proper type of RFC since this describes the architecture for L4S, while other Experimental RFCs describe the transport behaviors for use of the L4S identifier and DualQ that is one of the possible queueing options compatible with this architecture.

(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: (from abstract)

  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.

Working Group Summary:

The working group largely supports and is enthusiastic about L4S technology, which this document is a part of.  It was last called along with 2 other L4S documents.  There is a wider than normal level of support that has been expressed for this work, but it is not unanimous.  There are also some WG participants who have concerns about L4S or prefer an alternative approach.  The working group had many long email threads and conducted several interim meetings focused on L4S, its goals, technical challenges, and concerns with the approach and potential impact on Internet safety.  Full agreement was not obtained in all cases, but significant work was done to address the issues that were agreed upon, and each concern was considered in detail by the working group, even if some resolutions were not unanimously agreed with.

Document Quality:

There are multiple existing implementations of the technology described, and around 25 vendors and operators have indicated intentions to experiment with the overall L4S technology.

Personnel:

Wesley Eddy is the document shepherd and Martin Duke is the responsible 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 document myself, and believe it is ready for publication.  In addition, both other TSVWG co-chairs have closely reviewed and commented on earlier revisions of the document.

(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.

Since the document deals with transport, congestion control, packet marking, and queuing behavior, there can be security, operations, internet, and routing area interests.  There has been a healthy mix of academic, industry/vendor, and operator participation in this work, and a breadth of reviews have been incorporated.

(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.

There are no personal concerns of my own.  However, there have been concerns raised in the working group, discussed in question 9 below.

(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.

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

No.

(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?

There was a combined last call for this and the other two main L4S documents.  During that last call, it was clear that while a majority strongly supports the work and is eager to experiment with the technology, there are still also a number of participants who have concerns and/or prefer alternatives to L4S.  The working group devoted considerable time, including multiple focused interim meetings in order to understand objections and try to address or mitigate all concerns.  It is clear that while there are still some technical disagreements, there is a great deal of support and even wider than normal support for going forward with this work; spanning industry, including vendors, network operators, and congestion control researchers.

There were very specific technical concerns and disagreements with the other 2 L4S drafts (on the ECN usage and DualQ).  Specific concerns related to the content of those drafts are discussed in their writeups.
- In this particular document there were some early objections related to use of the term "classic" for traditional non-L4S transports and queues, though no superior term was able to be agreed on, and only a small number of people seemed unhappy with "classic".
- More substantially, there were concerns raised about the overall state of development and study of the combined L4S architecture elements, particularly the compliant transport protocols.  The TCP Prague reference code had some issues discovered (and fixed), and some of the working group participants did not feel like it was mature enough nor were the results of tests encouraging enough for them to support L4S advancing.  Note that other L4S transports beyond just TCP Prague have been under development by other groups, who reviewed the L4S drafts and reported on their capabilities to meet L4S requirements with their transports.
- The selection of the L4S identifier (in the companion ecn-l4s-id document) is not specific to this architecture draft, but is at the root of a great deal of the lack of unanimous support.  Since the beginning of this work, it was well understood that enhancing ECN involves tradeoffs in the choice of header encodings selected, since there are limited options in terms of the header bits, codepoints, and other fields like DSCP that can be leveraged.  The working group went through a process of assessing the pros and cons of all of the options that were put on the table.  The different weights that participants attach to the importance of these tradeoffs seems to be a major source of the inability to unanimously agree on the particular L4S usage of ECT1 (and CE).  It was remarked in one WG meeting that we ideally would have 5 codepoints, but unfortunately need to live with 4 and engineer within that.
- Some of the objecting participants have proposed another technology (SCE) to enhance ECN differently, and incompatibly with L4S and this architecture.  After careful consideration and a focused interim, the working group strongly supported the use of ECT(1) as an input to classification as in L4S to enable low latency traffic identification.  SCE proponents believe their alternative approach also can control latency, but use ECT(1) as an output to indicate finer-grained levels of congestion.

One potential mitigation for some of these concerns is that the TSVWG plans to be an open forum for experimenters to continue to present data and other findings, where the WG can ask questions, explore whether specific concerns have manifested, and discuss potential further development and advancement of L4S along the Standards Track.

(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.)

Some participants may feel strongly enough against L4S to consider an appeal.

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

There are very minor ID nits that can be corrected during publication.  These are the instances reported of non-ASCII characters and the outdated references to the other L4S documents.

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

N/A.

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

Yes - all are informative.

(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 (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.

N/A.

(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 8126).

There are (correctly) no IANA considerations.

(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, YANG modules, etc.

N/A  - there are no formal languages used.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?

N/A.

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 1 November 2019.

(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?

Informational.  This is indicated properly and is the proper type of RFC since this describes the architecture for L4S, while other Experimental RFCs describe the transport behaviors for use of the L4S identifier and DualQ that is one of the possible queueing options compatible with this architecture.

(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: (from abstract)

  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.

Working Group Summary:

The working group largely supports and is enthusiastic about L4S technology, which this document is a part of.  It was last called along with 2 other L4S documents.  There is a wider than normal level of support that has been expressed for this work, but it is not unanimous.  There are also some WG participants who have concerns about L4S or prefer an alternative approach.  The working group had many long email threads and conducted several interim meetings focused on L4S, its goals, technical challenges, and concerns with the approach and potential impact on Internet safety.  Full agreement was not obtained in all cases, but significant work was done to address the issues that were agreed upon, and each concern was considered in detail by the working group, even if some resolutions were not unanimously agreed with.

Document Quality:

There are multiple existing implementations of the technology described, and around 25 vendors and operators have indicated intentions to experiment with the overall L4S technology.

Personnel:

Wesley Eddy is the document shepherd and Martin Duke is the responsible 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 document myself, and believe it is ready for publication.  In addition, both other TSVWG co-chairs have closely reviewed and commented on earlier revisions of the document.

(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.

Since the document deals with transport, congestion control, packet marking, and queuing behavior, there can be security, operations, internet, and routing area interests.  There has been a healthy mix of academic, industry/vendor, and operator participation in this work, and a breadth of reviews have been incorporated.

(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.

There are no personal concerns of my own.  However, there have been concerns raised in the working group, discussed in question 9 below.

(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.

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

No.

(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?

There was a combined last call for this and the other two main L4S documents.  During that last call, it was clear that while a majority strongly supports the work and is eager to experiment with the technology, there are still also a number of participants who have concerns and/or prefer alternatives to L4S.  The working group devoted considerable time, including multiple focused interim meetings in order to understand objections and try to address or mitigate all concerns.  It is clear that while there are still some technical disagreements, there is a great deal of support and even wider than normal support for going forward with this work; spanning industry, including vendors, network operators, and congestion control researchers.

There were very specific technical concerns and disagreements with the other 2 L4S drafts (on the ECN usage and DualQ).  Specific concerns related to the content of those drafts are discussed in their writeups.
- In this particular document there were some early objections related to use of the term "classic" for traditional non-L4S transports and queues, though no superior term was able to be agreed on, and only a small number of people seemed unhappy with "classic".
- More substantially, there were concerns raised about the overall state of development and study of the combined L4S architecture elements, particularly the compliant transport protocols.  The TCP Prague reference code had some issues discovered (and fixed), and some of the working group participants did not feel like it was mature enough nor were the results of tests encouraging enough for them to support L4S advancing.  Note that other L4S transports beyond just TCP Prague have been under development by other groups, who reviewed the L4S drafts and reported on their capabilities to meet L4S requirements with their transports.
- Some of the objecting participants have proposed another technology (SCE) to enhance ECN differently, and incompatibly with L4S and this architecture.  After careful consideration and a focused interim, the working group strongly supported the use of ECT(1) as an input to classification as in L4S to enable low latency traffic identification.  SCE proponents believe their alternative approach also can control latency, but use ECT(1) as an output to indicate finer-grained levels of congestion.

One potential mitigation for some of these concerns is that the TSVWG plans to be an open forum for experimenters to continue to present data and other findings, where the WG can ask questions, explore whether specific concerns have manifested, and discuss potential further development and advancement of L4S along the Standards Track.

(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.)

Some participants may feel strongly enough against L4S to consider an appeal.

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

There are very minor ID nits that can be corrected during publication.  These are the instances reported of non-ASCII characters and the outdated references to the other L4S documents.

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

N/A.

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

Yes - all are informative.

(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 (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.

N/A.

(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 8126).

There are (correctly) no IANA considerations.

(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, YANG modules, etc.

N/A  - there are no formal languages used.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?

N/A.

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 1 November 2019.

(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?

Informational.  This is indicated properly and is the proper type of RFC since this describes the architecture for L4S, while other Experimental RFCs describe the transport behaviors for use of the L4S identifier and DualQ that is one of the possible queueing options compatible with this architecture.

(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: (from abstract)

  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.

Working Group Summary:

The working group largely supports and is enthusiastic about L4S technology, which this document is a part of.  It was last called along with 2 other L4S documents.  There is a wider than normal level of support that has been expressed for this work, but it is not unanimous.  There are also some WG participants who have concerns about L4S or prefer an alternative approach.  The working group had many long email threads and conducted several interim meetings focused on L4S, its goals, technical challenges, and concerns with the approach and potential impact on Internet safety.  Full agreement was not obtained in all cases, but significant work was done to address the issues that were agreed upon, and each concern was considered in detail by the working group, even if some were not widely agreed with.

Document Quality:

There are multiple implementations of the architecture described in the document.  Several vendors and network operators have indicated intentions to experiment with this technology.

Personnel:

Wesley Eddy is the document shepherd and Martin Duke is the responsible 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 document myself, and believe it is ready for publication.

(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.

Since the document deals with transport, congestion control, packet marking, and queuing behavior, there can be security, operations, internet, and routing area interests.  There has been a healthy mix of academic, industry/vendor, and operator participation in this work, and a breadth of reviews have been incorporated.

(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.

There are no personal concerns of my own.  However, there have been concerns raised in the working group, discussed in question 9 below.

(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.

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

No.

(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?

There was a combined last call for this and the other two main L4S documents.  During that last call, it was clear that while a majority strongly supports the work and is eager to experiment with the technology, there are still also a number of participants who have concerns and/or prefer alternatives to L4S.  The working group devoted considerable time, including multiple focused interim meetings in order to understand objections and try to address or mitigate all concerns.  It is clear that while there are still some technical disagreements, there is a great deal of support and even wider than normal support for going forward with this work; spanning industry, including vendors, network operators, and congestion control researchers.

There were very specific technical concerns and disagreements with the other 2 L4S drafts (on the ECN usage and DualQ).  Specific concerns related to the content of those drafts are discussed in their writeups.
- In this particular document there were some early objections related to use of the term "classic" for traditional non-L4S transports and queues, though no superior term was able to be agreed on, and only a small number of people seemed unhappy with "classic".
- More substantially, there were concerns raised about the overall state of development and study of the combined L4S architecture elements, particularly the compliant transport protocols.  The TCP Prague reference code had some issues discovered (and fixed), and some of the working group participants did not feel like it was mature enough nor were the results of tests encouraging enough for them to support L4S advancing.  Note that other L4S transports beyond just TCP Prague have been under development by other groups, who reviewed the L4S drafts and reported on their capabilities to meet L4S requirements with their transports.
- Some of the objecting participants have proposed another technology (SCE) to enhance ECN differently, and incompatibly with L4S and this architecture.  After careful consideration and a focused interim, the working group strongly supported the use of ECT(1) as an input to classification as in L4S to enable low latency traffic identification.  SCE proponents believe their alternative approach also can control latency, but use ECT(1) as an output to indicate finer-grained levels of congestion.

One potential mitigation for some of these concerns is that the TSVWG plans to be an open forum for experimenters to continue to present data and other findings, where the WG can ask questions, explore whether specific concerns have manifested, and discuss potential further development and advancement of L4S along the Standards Track.

(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.)

Some participants may feel strongly enough against L4S to consider an appeal.

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

There are only very minor nits noted for outdated document references, that can easily be fixed in conjunction with AD review comments.

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

N/A.

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

Yes - all are informative.

(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 (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.

N/A.

(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 8126).

There are (correctly) no IANA considerations.

(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, YANG modules, etc.

N/A  - there are no formal languages used.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?

N/A.

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 1 November 2019.

(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?

Informational.  This is indicated properly and is the proper type of RFC since this describes the architecture for L4S, while other Experimental RFCs describe the transport behaviors for use of the L4S identifier and DualQ that is one of the possible queueing options compatible with this architecture.

(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: (from abstract)

  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.

Working Group Summary:

The working group largely supports and is enthusiastic about L4S technology, which this document is a part of.  It was last called along with 2 other L4S documents.  There is a wider than normal level of support that has been expressed for this work, but it is not unanimous.  There are also some WG participants who have concerns about L4S or prefer an alternative approach.  The working group had many long email threads and conducted several interim meetings focused on L4S, its goals, technical challenges, and concerns with the approach and potential impact on Internet safety.  Full agreement was not obtained in all cases, but significant work was done to address the issues that were agreed upon, and each concern was considered in detail by the working group, even if some were not widely agreed with.

Document Quality:

There are multiple implementations of the architecture described in the document.  Several vendors and network operators have indicated intentions to experiment with this technology.

Personnel:

Wesley Eddy is the document shepherd and Martin Duke is the responsible 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 document myself, and believe it is ready for publication.

(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.

Since the document deals with transport, congestion control, packet marking, and queuing behavior, there can be security, operations, internet, and routing area interests.  There has been a healthy mix of academic, industry/vendor, and operator participation in this work, and a breadth of reviews have been incorporated.

(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.

There are no personal concerns of my own.  However, there have been concerns raised in the working group, discussed in question 9 below.

(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.

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

No.

(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?

There was a combined last call for this and the other two main L4S documents.  During that last call, it was clear that while a majority strongly supports the work and is eager to experiment with the technology, there are still also a number of participants who have concerns and/or prefer alternatives to L4S.  The working group devoted considerable time, including multiple focused interim meetings in order to understand objections and try to address or mitigate all concerns.  It is clear that while there are still some technical disagreements, there is a great deal of support and even wider than normal support for going forward with this work; spanning industry, including vendors, network operators, and congestion control researchers.

There were very specific technical concerns and disagreements with the other 2 L4S drafts (on the ECN usage and DualQ).  Specific concerns related to the content of those drafts are discussed in their writeups.
- In this particular document there were some early objections related to use of the term "classic" for traditional non-L4S transports and queues, though no superior term was able to be agreed on, and only a small number of people seemed unhappy with "classic".
- More substantially, there were concerns raised about the overall state of development and study of the combined L4S architecture elements, particularly the compliant transport protocols.  The TCP Prague reference code had some issues discovered (and fixed), and some of the working group participants did not feel like it was mature enough nor were the results of tests encouraging enough for them to support L4S advancing.  Note that other L4S transports beyond just TCP Prague have been under development by other groups, who reviewed the L4S drafts and reported on their capabilities to meet L4S requirements with their transports.
- Some of the objecting participants have proposed another technology (SCE) to enhance ECN differently, and incompatibly with L4S and this architecture.  After careful consideration and a focused interim, the working group strongly supported the goal of vastly reducing latency that is inherent to L4S but not SCE.

(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.)

Some participants may feel strongly enough against L4S to consider an appeal.

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

There are only very minor nits noted for outdated document references, that can easily be fixed in conjunction with AD review comments.

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

N/A.

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

Yes - all are informative.

(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 (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.

N/A.

(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 8126).

There are (correctly) no IANA considerations.

(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, YANG modules, etc.

N/A  - there are no formal languages used.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?

N/A.

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 1 November 2019.

(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?

Informational.  This is indicated properly and is the proper type of RFC since this describes the architecture for L4S, while other Experimental RFCs describe the transport behaviors for use of the L4S identifier and DualQ that is one of the possible queueing options compatible with this architecture.

(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: (from abstract)

  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.

Working Group Summary:

The working group largely supports and is enthusiastic about L4S technology, which this document is a part of.  It was last called along with 2 other L4S documents.  There is a wider than normal level of support that has been expressed for this work, but it is not unanimous.  There are also some WG participants who have concerns about L4S or prefer an alternative approach.  The working group had many long email threads and conducted several interim meetings focused on L4S, its goals, technical challenges, and concerns with the approach and potential impact on Internet safety.  Full agreement was not obtained in all cases, but significant work was done to address the issues that were agreed upon, and each concern was considered in detail by the working group, even if some were not widely agreed with.

Document Quality:

There are multiple implementations of the architecture described in the document.  Several vendors and network operators have indicated intentions to experiment with this technology.

Personnel:

Wesley Eddy is the document shepherd and Martin Duke is the responsible 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 document myself, and believe it is ready for publication.

(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.

Since the document deals with transport, congestion control, packet marking, and queuing behavior, there can be security, operations, internet, and routing area interests.  There has been a healthy mix of academic, industry/vendor, and operator participation in this work, and a breadth of reviews have been incorporated.

(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.

There are no personal concerns of my own.  However, there have been concerns raised in the working group, discussed in question 9 below.

(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.

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

No.

(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?

TODO

(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.)

Some participants may feel strongly enough against L4S to consider an appeal.

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

There are only very minor nits noted for outdated document references, that can easily be fixed in conjunction with AD review comments.

(12) Describe how the document meets any required formal review criteria, such as the MIB Doctor, YANG 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 (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.

N/A.

(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 8126).

There are (correctly) no IANA considerations.

(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, YANG modules, etc.

N/A  - there are no formal languages used.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?

N/A.

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 1 November 2019.

(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?

Informational.  This is indicated properly and is the proper type of RFC since this describes the architecture for L4S, while other Experimental RFCs describe the transport behaviors for use of the L4S identifier and DualQ that is one of the possible queueing options compatible with this architecture.

(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: (from abstract)

  This document describes the L4S architecture, which enables Internet
  applications to achieve Low queuing Latency, Low Loss, and Scalable
  throughput (L4S).  The insight on which L4S is based is that the root
  cause of queuing delay is in the congestion controllers of senders,
  not in the queue itself.  With the L4S architecture all Internet
  applications could (but do not have to) transition away from
  congestion control algorithms that cause substantial queuing delay,
  to a new class of congestion controls that induce very little
  queuing, aided by explicit congestion signalling from the network.
  This new class of congestion controls can provide low latency for
  capacity-seeking flows, so applications can achieve both high
  bandwidth and low latency.

  The architecture primarily concerns incremental deployment.  It
  defines mechanisms that allow the new class of L4S congestion
  controls to coexist with 'Classic' congestion controls in a shared
  network.  These mechanisms aim to ensure that the latency and
  throughput performance using an L4S-compliant congestion controller
  is usually much better (and rarely worse) than performance would have
  been using a 'Classic' congestion controller, and that competing
  flows continuing to use 'Classic' controllers are typically not
  impacted by the presence of L4S.  These characteristics are important
  to encourage adoption of L4S congestion control algorithms and L4S
  compliant network elements.

  The L4S architecture consists of three components: network support to
  isolate L4S traffic from classic traffic; protocol features that
  allow network elements to identify L4S traffic; and host support for
  L4S congestion controls.

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?

TODO

Document Quality:

There are multiple implementations of the architecture described in the document.  Several vendors and network operators have indicated intentions to experiment with this technology.

Personnel:

Wesley Eddy is the document shepherd and Martin Duke is the responsible 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 document myself, and believe it is ready for publication.

(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.

Since the document deals with transport, congestion control, packet marking, and queuing behavior, there can be security, operations, internet, and routing area interests.  There has been a healthy mix of academic, industry/vendor, and operator participation in this work, and a breadth of reviews have been incorporated.

(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.

There are no personal concerns of my own.  However, there have been concerns raised in the working group, discussed in question 9 below.

(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.

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

No.

(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?

TODO

(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.)

Some participants may feel strongly enough against L4S to consider an appeal.

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

TODO

(12) Describe how the document meets any required formal review criteria, such as the MIB Doctor, YANG 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 (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.

N/A.

(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 8126).

TODO

(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, YANG modules, etc.

N/A  - there are no formal languages used.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?

N/A.