TCP Usage Guidance in the Internet of Things (IoT)
draft-ietf-lwig-tcp-constrained-node-networks-13

[Ballot comment]
Thanks for addressing my DISCUSS.

Original comments, since resolved:

Please address the tsv review comments.

Sec 4.2.3
s/Disabling Delayed ACKs at the
  sender allows an immediate ACK/Disabling Delayed ACKs at the
  request sender allows an immediate ACK

Sec 4.3.1
  When a multiple-segment window is used, the receiver will need to
  manage the reception of possible out-of-order received segments,
  requiring sufficient buffer space.

It's worth pointing out here that even a 1 MSS window should also manage out-of-order arrival, as the sender may send multiple sub-MSS packets that fit in the window. (On the other hand, the receiver is free to simply drop the out-of-order segment, thus forcing a retransmission).

Sec 4.3.3.1
s/since with SACK recovery/since SACK recovery

[Ballot comment]
Updated position as the previous DISCUSS point below (kept for archives) and COMMENTs have been addressed

-éric


Thank you for the work put into this document. It is an important topic and the document is both easy to ready and detailed.

Please find below one trivial DISCUSS point and a couple of non-blocking COMMENT points but please also check:
- Ines Robles IoT directorate review:
https://datatracker.ietf.org/doc/review-ietf-lwig-tcp-constrained-node-networks-11-iotdir-telechat-robles-2020-10-20/
- Bernie Volz Internet directorate review:
https://datatracker.ietf.org/doc/review-ietf-lwig-tcp-constrained-node-networks-11-intdir-telechat-volz-2020-10-20/

I hope that this helps to improve the document,

Regards,

== COMMENTS ==

Should a reference to RFC 8900 be added in the MTU discussion in section 4.1 ?

-- Section 2 --
As noted by many, the BCP 14 boiler plate is the old one and the normative terminology is not used in this informational document. => remove it ?

[Ballot discuss]
Thank you for the work put into this document. It is an important topic and the document is both easy to ready and detailed.

Please find below one trivial DISCUSS point and a couple of non-blocking COMMENT points but please also check:
- Ines Robles IoT directorate review:
https://datatracker.ietf.org/doc/review-ietf-lwig-tcp-constrained-node-networks-11-iotdir-telechat-robles-2020-10-20/
- Bernie Volz Internet directorate review:
https://datatracker.ietf.org/doc/review-ietf-lwig-tcp-constrained-node-networks-11-intdir-telechat-volz-2020-10-20/

I hope that this helps to improve the document,

Regards,

-éric

== DISCUSS ==

Please replace all RFC 2460 references to RFC 8200. Trivial to fix ;-)

[Ballot discuss]
Thank you for the work put into this document. It is an important topic and the document is both easy to ready and detailed.

Please find below one trivial DISCUSS point and a couple of non-blocking COMMENT points but please also check:
- Ines Robles IoT directorate review:
https://datatracker.ietf.org/doc/review-ietf-lwig-tcp-constrained-node-networks-11-iotdir-telechat-robles-2020-10-20/
- Bernie Volz Internet directorate review:
https://datatracker.ietf.org/doc/review-ietf-lwig-tcp-constrained-node-networks-11-intdir-telechat-volz-2020-10-20/

I hope that this helps to improve the document,

Regards,

-éric

== DISCUSS ==

Please replace all RFC 4260 reference to RFC 8200. Trivial to fix ;-)

[Ballot comment]
== COMMENTS ==

Should a reference to RFC 8900 be added in the MTU discussion in section 4.1 ?

-- Section 2 --
As noted by many, the BCP 14 boiler plate is the old one and the normative terminology is not used in this informational document. => remove it ?

[Ballot comment]
Thanks for a useful document.  I just have a few editorial things here:

— Section 1 —

  However, TCP has been
  criticized (often, unfairly) as a protocol for the IoT.  In fact,
  some TCP features are not optimal for IoT scenarios, such as
  relatively long header size, unsuitability for multicast, and always-
  confirmed data delivery.  However, …

Both of these sentences have nit-level problems that make them a bit off.  The first sounds like the criticism is that TCP is a protocol for IoT (rather than that it’s not suitable for that usage).  The second has the examples misplaced, so it look as though they’re examples of IoT scenarios (rather than examples of TCP features).  And “in fact” has the wrong feel here: it would normally be used to contradict the previous sentence, not to explain it.  (And two “however”s in close proximity also feels awkward)  I suggest this fix:

NEW
  TCP has been
  criticized, often unfairly, as a protocol that’s unsuitable for the
  IoT.  It is true that some TCP features, such as its relatively long
  header size, unsuitability for multicast, and always-confirmed data
  delivery, are not optimal for IoT scenarios.  However, …
END

  TCP is also used by non-IETF application-
  layer protocols in the IoT space such as the Message Queue Telemetry
  Transport (MQTT) and its lightweight variants.

It’s “Message Queuing Telemetry Transport”, and an informative reference to ISO/IEC 20922  wouldn’t be a bad thing.

[Ballot comment]
[edited to properly attribute the Discuss holder]
Mostly just editorial nits, but please see the comment on Section 5.3.

Section 2

(I believe the existence of the RFC 8174 version of the BCP 14
boilerplate has already been noted.)

Section 3.2

  or devices with a pool of multiple send/receive buffers.  In the
  latter case, it is possible that buffers also be shared for other
  protocols.

nit: s/be/are/ (or any number of other minor tweaks)

  One key use case for the use of TCP in CNNs is a model where

nit: "use case for the use" is probably redundant: "use case for TCP in
CNNs" seems like it would work okay.

  middlebox (e.g. a firewall, NAT, etc.).  Figure 1 illustrates such
  scenario.  Note that the scenario is asymmetric, as the unconstrained

nit: "such a scenario".

Section 3.3

  o  Unidirectional transfers: An IoT device (e.g. a sensor) can send
      (repeatedly) updates to the other endpoint.  Not in every case
      there is a need for an application response back to the IoT
      device.

(editorial) I suggest "There is not always a need for an application
response back to the IoT device".

Section 4.1.1

  smaller than 1220 bytes (e.g. not larger than 1200 bytes).  Note that
  it is advised for TCP implementations to consume payload space
  instead of increasing datagram size when including IP or TCP options
  in an IP packet to be sent [RFC6691].  Therefore, the suggestion of

[my reading of RFC 6691 is that it was required to consume payload
space, but only recommended to account for this behavior when
advertising MSS.  I guess Martin covered this in his Discuss point already, though.]

Section 5.3

  The message and latency overhead that stems from using a sequence of
  short-lived connections could be reduced by TCP Fast Open (TFO)
  [RFC7413], which is an experimental TCP extension, at the expense of
  increased implementation complexity and increased TCP Control Block
  (TCB) size.  TFO allows data to be carried in SYN (and SYN-ACK)

We should probably make at least a passing mention of the TFO security
considerations here, possibly with some discussion of why they are less
consequential for certain CNNs than in general.  (Note that the security
considerations for TFO are not limited to just the risk of replay, and
that there are privacy considerations for the TFO cookie being used to
link together multiple TCP connections between the same endpoints.)

Section 10.1

RFC 3819 may not need to be listed as normative, given the nature of the
one place in which it is referenced.

Similarly, we don't say much about TCP-AP other than it exists, so RFC
5925 may not need to be normative either.

Section 10.2

RFC 6092 appears to not be referenced from anywhere?
idnits notes a couple other reference-related issues.

[Ballot comment]
Mostly just editorial nits, but please see the comment on Section 5.3.

Section 2

(I believe the existence of the RFC 8174 version of the BCP 14
boilerplate has already been noted.)

Section 3.2

  or devices with a pool of multiple send/receive buffers.  In the
  latter case, it is possible that buffers also be shared for other
  protocols.

nit: s/be/are/ (or any number of other minor tweaks)

  One key use case for the use of TCP in CNNs is a model where

nit: "use case for the use" is probably redundant: "use case for TCP in
CNNs" seems like it would work okay.

  middlebox (e.g. a firewall, NAT, etc.).  Figure 1 illustrates such
  scenario.  Note that the scenario is asymmetric, as the unconstrained

nit: "such a scenario".

Section 3.3

  o  Unidirectional transfers: An IoT device (e.g. a sensor) can send
      (repeatedly) updates to the other endpoint.  Not in every case
      there is a need for an application response back to the IoT
      device.

(editorial) I suggest "There is not always a need for an application
response back to the IoT device".

Section 4.1.1

  smaller than 1220 bytes (e.g. not larger than 1200 bytes).  Note that
  it is advised for TCP implementations to consume payload space
  instead of increasing datagram size when including IP or TCP options
  in an IP packet to be sent [RFC6691].  Therefore, the suggestion of

[my reading of RFC 6691 is that it was required to consume payload
space, but only recommended to account for this behavior when
advertising MSS.  I guess Erik covered this in his Discuss point already, though.]

Section 5.3

  The message and latency overhead that stems from using a sequence of
  short-lived connections could be reduced by TCP Fast Open (TFO)
  [RFC7413], which is an experimental TCP extension, at the expense of
  increased implementation complexity and increased TCP Control Block
  (TCB) size.  TFO allows data to be carried in SYN (and SYN-ACK)

We should probably make at least a passing mention of the TFO security
considerations here, possibly with some discussion of why they are less
consequential for certain CNNs than in general.  (Note that the security
considerations for TFO are not limited to just the risk of replay, and
that there are privacy considerations for the TFO cookie being used to
link together multiple TCP connections between the same endpoints.)

Section 10.1

RFC 3819 may not need to be listed as normative, given the nature of the
one place in which it is referenced.

Similarly, we don't say much about TCP-AP other than it exists, so RFC
5925 may not need to be normative either.

Section 10.2

RFC 6092 appears to not be referenced from anywhere?
idnits notes a couple other reference-related issues.

[Ballot comment]
Thanks for this practical guidance to implementers.  A few minor nits:
S
ection 4.1.2. Typo. s/bandwitdh/bandwidth/

Section 4.2.1. Editorial.  s/implementation are/implementations are/

Section 6. Typo. s/ targetted/targeted/

Section 8.7.  Typo. s/ differrent/different/

[Ballot comment]
Hi,

Thank you for this document.  It is somewhat outside my area of expertise, but I do not see any network management related issues.

One minor comment:

    3.2.  Usage scenarios

      There are different deployment and usage scenarios for CNNs.  Some
      CNNs follow the star topology, whereby one or several hosts are
      linked to a central device that acts as a router connecting the CNN
      to the Internet.  CNNs may also follow the multihop topology
      [RFC6606].

Perhaps: "Alternatively, CNNs may also follow ... ", otherwise it feels like this paragraph stops quite abruptly, whereas from the first couple of sentences I was expecting it to say a bit more about the different deployment scenarios.

Regards,
Rob

[Ballot discuss]
In Sec 4.1.1:

  An IPv6 datagram size exceeding 1280 bytes can be avoided by setting
  the TCP MSS not larger than 1220 bytes.  This assumes that the remote
  sender will use no TCP options, aside from possibly the MSS option,
  which is only used in the initial TCP SYN packet.

  In order to accommodate unrequested TCP options that may be used by
  some TCP implementations, a constrained device may advertise an MSS
  smaller than 1220 bytes (e.g. not larger than 1200 bytes).  Note that
  it is advised for TCP implementations to consume payload space
  instead of increasing datagram size when including IP or TCP options
  in an IP packet to be sent [RFC6691].  Therefore, the suggestion of
  advertising an MSS smaller than 1220 bytes is likely to be
  overcautious and its suitability should be considered carefully.

I would delete everything after the first sentence in this excerpt. While
RFC6691 is informational, it clarifies RFC1122, which is a standard, and
Sec 4.2.2.6 is quite clear that senders MUST consider TCP and IP option
length when sizing TCP payloads.

Absent any evidence that there are TCP endpoints or middleboxes that are
violating RFC1122, further reducing the MSS because someone might be
violating it is excessive.

[Ballot comment]
Please address the tsv review comments.

Sec 4.2.3
s/Disabling Delayed ACKs at the
  sender allows an immediate ACK/Disabling Delayed ACKs at the
  request sender allows an immediate ACK

Sec 4.3.1
  When a multiple-segment window is used, the receiver will need to
  manage the reception of possible out-of-order received segments,
  requiring sufficient buffer space.

It's worth pointing out here that even a 1 MSS window should also manage out-of-order arrival, as the sender may send multiple sub-MSS packets that fit in the window. (On the other hand, the receiver is free to simply drop the out-of-order segment, thus forcing a retransmission).

Sec 4.3.3.1
s/since with SACK recovery/since SACK recovery

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

(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: 
  This document provides guidance on how to implement and use the
  Transmission Control Protocol (TCP) in Constrained-Node Networks
  (CNNs, defined in RFC7228), which are a characterstic of the Internet of Things (IoT).
  Such environments require a lightweight TCP implementation and may
  not make use of optional functionality.  This document explains a
  number of known and deployed techniques to simplify a TCP stack as
  well as corresponding tradeoffs.  The objective is to help embedded
  developers with decisions on which TCP features to use.


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

Working Group Summary:  NONE.

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?

Document Quality: 
  This document is not a protocol specification, and it intends to  provide guidance on how to implement and configure TCP stack, as well as on how TCP is advisable to be used by applications. This document has been reviewed thoroughly by the experts in both LWIG and TCPM working groups during the WGLC.  Markku Kojo, a long-time IETF transport expert, has provided a thorough review.  Many other provided comments which has been reflected in the current version of this draft. 
 
Are there existing implementations of the protocol? Have a significant number of vendors indicated their plan to implement the specification? Are there any reviewers that merit special mention as having done a thorough review, e.g., one that resulted in important changes or a conclusion that the document had no substantive issues? If there was a MIB Doctor, YANG Doctor, Media Type or other expert review, what was its course (briefly)? In the case of a Media Type review, on what date was the request posted?

Personnel:

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

Zhen Cao is the Shepherd,  and Erik Kline 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.

The draft is very useful for many developers using or considering of using TCP in IoT scenarios.  It explains a number of techniques including Maximum Segment Size (MSS), Delayed ACK and RTO calculation for single-MSS stacks, and provides some general and important recommendations for using TCP in CNNs.  It also summarizes features of some popular light-weight TCP/IP implementations.  All of these are quite useful to developers in this area, and I believe many pitfalls can be avoided by following the advice in this document.

For the very infrequent request-response application flows, if the developers do not know the This document explains a number of TCP features in terms of their impacts to the very simply

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

No, given many known experts have provided reviews and comments.

(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.

None.

(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.

None

(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, all authors have confirmed by replying the poll email on the LWIG WG public mailing list.

(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?

This document holds a strong consensus with the group.

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

No.

(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.

No essential issues found.

(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?
NONE.

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

NONE.

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

No.

(17) Describe the Document Shepherd's review of the IANA considerations section, especially with regard to its consistency with the body of the document. Confirm that all protocol extensions that the document makes are associated with the appropriate reservations in IANA registries. Confirm that any referenced IANA registries have been clearly identified. Confirm that newly created IANA registries include a detailed specification of the initial contents for the registry, that allocations procedures for future registrations are defined, and a reasonable name for the new registry has been suggested (see RFC 8126).

There is no IANA requests in this document.

(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

(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

Technical Summary: 
  This document provides guidance on how to implement and use the
  Transmission Control Protocol (TCP) in Constrained-Node Networks
  (CNNs, defined in RFC7228), which are a characterstic of the Internet of Things (IoT).
  Such environments require a lightweight TCP implementation and may
  not make use of optional functionality.  This document explains a
  number of known and deployed techniques to simplify a TCP stack as
  well as corresponding tradeoffs.  The objective is to help embedded
  developers with decisions on which TCP features to use.

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

The IANA Functions Operator has reviewed draft-ietf-lwig-tcp-constrained-node-networks-10, which is currently in Last Call, and has the following comments:

The IANA Services Operator notes that this document does not contain a standard IANA Considerations section. After examining the draft, we understand that, upon approval of this document, there are no IANA Actions that need completion.

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

Thank you,

Sabrina Tanamal
Senior IANA Services Specialist

The following Last Call announcement was sent out (ends 2020-09-30):

From: The IESG
To: IETF-Announce
CC: ek.ietf@gmail.com, zhencao.ietf@gmail.com, draft-ietf-lwig-tcp-constrained-node-networks@ietf.org, lwip@ietf.org, Zhen Cao , lwig-chairs@ietf.org
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (TCP Usage Guidance in the Internet of Things (IoT)) to Informational RFC


The IESG has received a request from the Light-Weight Implementation Guidance
WG (lwig) to consider the following document: - 'TCP Usage Guidance in the
Internet of Things (IoT)'
  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 2020-09-30. 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 provides guidance on how to implement and use the
  Transmission Control Protocol (TCP) in Constrained-Node Networks
  (CNNs), which are a characterstic of the Internet of Things (IoT).
  Such environments require a lightweight TCP implementation and may
  not make use of optional functionality.  This document explains a
  number of known and deployed techniques to simplify a TCP stack as
  well as corresponding tradeoffs.  The objective is to help embedded
  developers with decisions on which TCP features to use.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-lwig-tcp-constrained-node-networks/



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

I apologize for the delay in getting to this review.

This document seems generally very well written and I think ready for
IETF LC.  In the meantime, here are some comments that are just style
nits; uploading a new version with these or similar changes during LC
shouldn't confuse anybody, I expect.

I'm going to change the substate to "Revised I-D Needed" while I ping
the transport ADs to make sure they're aware we're proceeding.

Thanks!

[ shepherd write-up ]

* Consider updating the shepherd write-up, as Suresh is no longer
  the relevant AD.

[ section 4.1.1 ]

* Consider whether this section should note something along the lines
  of: use of MTUs that exceed the standard "Internet MTU" of 1500 for
  communication paths to/through the broader Internet might have to
  incur Path MTU discovery overhead (or rely upon beneficent MSS
  clamping somewhere).

[ section 4.1.2 ]

* s/Less lost packets/Fewer lost packets | Less packet loss/

[ section 4.2.3 ]

* Perhaps just s/Furthermore, the overhead/The overhead/

[ section 4.3.1 ]

* You expand TCB on second use, in section 5.2.  You might move that
  acronym expansion here (first use).

  [Note to self: ask to add TCB to the RFC Editor's abbreviations list.]

[ section 5.3 ]

* s/a TCP connection for long time/a TCP connection for a long time/

[ section 8.1 ]

* The uIP implementation includes "IP": should this be read as "IPv4",
  or is there also an IPv6 stack?

[ section 8.2 ]

* The lwIP implementation includes "IP": should this be read as "IPv4",
  or is there also an IPv6 stack?

[ section 8.4 ]

* s/important as platform/important as a platform/

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

(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: 
  This document provides guidance on how to implement and use the
  Transmission Control Protocol (TCP) in Constrained-Node Networks
  (CNNs, defined in RFC7228), which are a characterstic of the Internet of Things (IoT).
  Such environments require a lightweight TCP implementation and may
  not make use of optional functionality.  This document explains a
  number of known and deployed techniques to simplify a TCP stack as
  well as corresponding tradeoffs.  The objective is to help embedded
  developers with decisions on which TCP features to use.


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

Working Group Summary:  NONE.

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?

Document Quality: 
  This document is not a protocol specification, and it intends to  provide guidance on how to implement and configure TCP stack, as well as on how TCP is advisable to be used by applications. This document has been reviewed thoroughly by the experts in both LWIG and TCPM working groups during the WGLC.  Markku Kojo, a long-time IETF transport expert, has provided a thorough review.  Many other provided comments which has been reflected in the current version of this draft. 
 
Are there existing implementations of the protocol? Have a significant number of vendors indicated their plan to implement the specification? Are there any reviewers that merit special mention as having done a thorough review, e.g., one that resulted in important changes or a conclusion that the document had no substantive issues? If there was a MIB Doctor, YANG Doctor, Media Type or other expert review, what was its course (briefly)? In the case of a Media Type review, on what date was the request posted?

Personnel:

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

Zhen Cao is the Shepherd,  and Suresh Krishnan 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.

The draft is very useful for many developers using or considering of using TCP in IoT scenarios.  It explains a number of techniques including Maximum Segment Size (MSS), Delayed ACK and RTO calculation for single-MSS stacks, and provides some general and important recommendations for using TCP in CNNs.  It also summarizes features of some popular light-weight TCP/IP implementations.  All of these are quite useful to developers in this area, and I believe many pitfalls can be avoided by following the advice in this document.

For the very infrequent request-response application flows, if the developers do not know the This document explains a number of TCP features in terms of their impacts to the very simply

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

No, given many known experts have provided reviews and comments.

(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.

None.

(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.

None

(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, all authors have confirmed by replying the poll email on the LWIG WG public mailing list.

(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?

This document holds a strong consensus with the group.

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

No.

(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.

No essential issues found.

(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?
NONE.

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

NONE.

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

No.

(17) Describe the Document Shepherd's review of the IANA considerations section, especially with regard to its consistency with the body of the document. Confirm that all protocol extensions that the document makes are associated with the appropriate reservations in IANA registries. Confirm that any referenced IANA registries have been clearly identified. Confirm that newly created IANA registries include a detailed specification of the initial contents for the registry, that allocations procedures for future registrations are defined, and a reasonable name for the new registry has been suggested (see RFC 8126).

There is no IANA requests in this document.

(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

(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

(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: 
  This document provides guidance on how to implement and use the
  Transmission Control Protocol (TCP) in Constrained-Node Networks
  (CNNs, defined in RFC7228), which are a characterstic of the Internet of Things (IoT).
  Such environments require a lightweight TCP implementation and may
  not make use of optional functionality.  This document explains a
  number of known and deployed techniques to simplify a TCP stack as
  well as corresponding tradeoffs.  The objective is to help embedded
  developers with decisions on which TCP features to use.


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

Working Group Summary:  NONE.

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?

Document Quality: 
  This document is not a protocol specification, and it intends to  provide guidance on how to implement and configure TCP stack, as well as on how TCP is advisable to be used by applications. This document has been reviewed thoroughly by the experts in both LWIG and TCPM working groups during the WGLC.  Markku Kojo, a long-time IETF transport expert, has provided a thorough review.  Many other provided comments which has been reflected in the current version of this draft. 
 
Are there existing implementations of the protocol? Have a significant number of vendors indicated their plan to implement the specification? Are there any reviewers that merit special mention as having done a thorough review, e.g., one that resulted in important changes or a conclusion that the document had no substantive issues? If there was a MIB Doctor, YANG Doctor, Media Type or other expert review, what was its course (briefly)? In the case of a Media Type review, on what date was the request posted?

Personnel:

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

Zhen Cao is the Shepherd,  and Suresh Krishnan 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.

The draft is very useful for many developers using or considering of using TCP in IoT scenarios.  It explains a number of techniques including Maximum Segment Size (MSS), Delayed ACK and RTO calculation for single-MSS stacks, and provides some general and important recommendations for using TCP in CNNs.  It also summarizes features of some popular light-weight TCP/IP implementations.  All of these are quite useful to developers in this area, and I believe many pitfalls can be avoided by following the advice in this document.

For the very infrequent request-response application flows, if the developers do not know the This document explains a number of TCP features in terms of their impacts to the very simply

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

No, given many known experts have provided reviews and comments.

(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.

None.

(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.

None

(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, all authors have confirmed by replying the poll email on the LWIG WG public mailing list.

(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?

This document holds a strong consensus with the group.

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

No.

(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.

No essential issues found.

(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?
NONE.

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

NONE.

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

No.

(17) Describe the Document Shepherd's review of the IANA considerations section, especially with regard to its consistency with the body of the document. Confirm that all protocol extensions that the document makes are associated with the appropriate reservations in IANA registries. Confirm that any referenced IANA registries have been clearly identified. Confirm that newly created IANA registries include a detailed specification of the initial contents for the registry, that allocations procedures for future registrations are defined, and a reasonable name for the new registry has been suggested (see RFC 8126).

There is no IANA requests in this document.

(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

(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