Datagram PLPMTUD for UDP Options
draft-ietf-tsvwg-udp-options-dplpmtud-15

[Ballot comment]
(correcting ballot from "no record" to "no objection", sorry for the noise)

Thanks for this document. Among other things, I appreciated the care you took to make it clear when you were quoting pre-existing normative requirements rather than imposing new ones.

I have one trivial and superficial gripe: I was bugged by the fact that in your diagram, the arcs on the left/Rx side are arrows pointing up:

^
|
+

But the ones on the right/Tx side are nondirected dangling lines:

+
|
|

Instead of arrows pointing down, which would be:

+
|
v

¯\_(ツ)_/¯

[Ballot comment]
Thanks for this document. Among other things, I appreciated the care you took to make it clear when you were quoting pre-existing normative requirements rather than imposing new ones.

I have one trivial and superficial gripe: I was bugged by the fact that in your diagram, the arcs on the left/Rx side are arrows pointing up:

^
|
+

But the ones on the right/Tx side are nondirected dangling lines:

+
|
|

Instead of arrows pointing down, which would be:

+
|
v

¯\_(ツ)_/¯

[Ballot comment]

# Éric Vyncke, INT AD, comments for draft-ietf-tsvwg-udp-options-dplpmtud-14
CC @evyncke

Thank you for the work put into this document.

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 Marten Seemann for the shepherd's write-up including the WG consensus *and* the justification of the intended status.

Other thanks to Brian Haberman, the Internet directorate reviewer (at my request), please consider this detailed int-dir review:
https://datatracker.ietf.org/doc/review-ietf-tsvwg-udp-options-dplpmtud-13-intdir-telechat-haberman-2025-02-11/ (and I have read Gorry's replies)

Please note that Henk Birkholz is the DNS directorate reviewer and you may want to consider this dns-dir review as well when it will be available (no need to wait for it though):
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-udp-options-dplpmtud/reviewrequest/21462/

I hope that this review helps to improve the document,

Regards,

-éric

## COMMENTS (non-blocking)

### Sequencing of UDP options drafts

It would have been nicer for the IESG evaluation to have draft-ietf-tsvwg-udp-options-39 in the same telechat as for this document ;-)

### Missing topics ?

This is perhaps mentioned in RFC 8899, but is this specification applicable to multicast traffic ?

Some words may be written about ECMP as this method works fine with ECMP.

### Section 3

```
Use of DPLPMTUD MUST be explicitly enabled by the application, for instance once an application has established connectivity and is ready to exchange data with the remote Upper Layer protocol.
```

Seems to indicate that this mechanism works *only* for bidirectional flows, i.e., not for a sender-only role (e.g., Syslog). Should this document be clear about this restriction (in the abstract and in the introduction)?

### Section 3.1

How can UDP talkers discover the RTT in `to send 1 per RTT` ?

### Section 3.3

I find weird the use of 'normally' in a specification `DPLPMTUD does not normally send more than one probe packet per timeout interval`. Should it rather be "per specification" ?

### Section 4.5

Probably due to my lack of knowledge in UDP, but I find probing with application data problematic, see below.

`include the corresponding RES Option in an Upper Layer protocol message that it returns to the requester` the "an ULP message" is rather vague... what if the reply comes minutes after the request ? What is dozens of replies are generated (should the RES be sent in the first, the last packets)

How can a receiver distinguish between:
- a sender not sending probes with application data (i.e., having no payload in the probe)
- a sender sending probes with application data but for once sending a UDP w/o application data (e.g., keeping a NAT happy)

### Section 5.2

The Packet-too-big section of RFC 8899 only checks for ports but in this case, should it also validate that the 4-octet token is present ? The text says that the token MUST be present but is rather light that in absence of the token in the PTB, the PTB is to be ignored. (I understand that I am splitting hair here).

## NITS (non-blocking / cosmetic)

### Byte vs. octet

I usually prefer the use of "octet" vs. "byte", but this is a matter of taste.

### Use of SVG graphics

To make a much nicer HTML rendering, suggest using the aasvg too to generate SVG graphics. It is worth a try ;-)

[Ballot comment]
# Internet AD comments for draft-ietf-tsvwg-udp-options-dplpmtud-14
CC @ekline

* comment syntax:
  - https://github.com/mnot/ietf-comments/blob/main/format.md

* "Handling Ballot Positions":
  - https://ietf.org/about/groups/iesg/statements/handling-ballot-positions/

## Comments

### S4.2

* "At the receiver, a received probe packet that does not carry
  application data does not form a part of the end-to-end transport
  data and is not delivered to the Upper Layer protocol (i.e.,
  application or protocol layered above UDP)."

  It is theoretically possible, however, that a UDP-Options-aware
  implementation could "deliver" a zero-length payload notification to
  the application, I presume (a la RFC 8085 S5)?

  I suppose a similar question applies to S4.4.

## Nits

### S3

* "less than of equal to" ->
  "less than or equal to"

### S3.1

* "Reception of a RES Option by the sender" ->
  "Reception of a RES Option by the REQ sender"

  or something, as there are two "senders" involved.

[Ballot comment]
First of all thanks to Brian Haberman for his INTDIR and to Robert Sparks for his SECDIR review. Both the reviews have provided comments that I think will help improve the draft. I look forward to the resolution of those comments and what needs to be incorported into the document.

The document is otherwise well-written and easy to understand. I have only these minor nits on the draft.

-------------------------------------------------------------------------------
NIT
-------------------------------------------------------------------------------

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.

Section 3, paragraph 11
> ,Min_PMTU | | Token Values & Probes, etc | +---------------------------+----+
>                                      ^^^
In American English, abbreviations like "etc." require a period.

Section 3, paragraph 12
> end | Events: ICMP, Interface MTU, etc +--------------------------------+ |
>                                    ^^^
In American English, abbreviations like "etc." require a period.

Section 4.1, paragraph 2
> be packet to elicit a positive acknowledgment that the path has delivered a
>                                ^^^^^^^^^^^^^^
Do not mix variants of the same word ("acknowledgment" and "acknowledgement")
within a single text.

Section 5.2, paragraph 1
> de the option, filtering on the path, etc). * (DPLPMTUD receiver uses applica
>                                      ^^^
In American English, abbreviations like "etc." require a period.

Section 5.2, paragraph 2
> is periodic feedback (e.g., one acknowledgment packet per RTT). It requires t
>                                ^^^^^^^^^^^^^^
Do not mix variants of the same word ("acknowledgment" and "acknowledgement")
within a single text.

IESG/Authors/WG Chairs:

IANA has completed its review of draft-ietf-tsvwg-udp-options-dplpmtud-13, 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,

David Dong
IANA Services Sr. Specialist

The following Last Call announcement was sent out (ends 2025-02-10):

From: The IESG
To: IETF-Announce
CC: draft-ietf-tsvwg-udp-options-dplpmtud@ietf.org, martenseemann@gmail.com, tsvwg-chairs@ietf.org, tsvwg@ietf.org, zahed.sarker.ietf@gmail.com
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (Datagram PLPMTUD for UDP Options) to Proposed Standard


The IESG has received a request from the Transport and Services Working Group
WG (tsvwg) to consider the following document: - 'Datagram PLPMTUD for UDP
Options'
  as Proposed Standard

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 2025-02-10. 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 specifies how a UDP Options sender implements Datagram
  Packetization Layer Path Maximum Transmission Unit Discovery
  (DPLPMTUD) as a robust method for Path Maximum Transmission Unit
  discovery.  This method uses the UDP Options packetization layer.  It
  allows an application to discover the largest size of datagram that
  can be sent across a network path.  It also provides a way to allow
  the application to periodically verify the current maximum packet
  size supported by a path and to update this when required.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-udp-options-dplpmtud/



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

# Shepherd Review \- DPLPMTUD for UDP Options

## Document History

1. Was the document considered in any WG, and if so, why was it not adopted as a work item there?

The document was only considered in TSVWG.

2. Was there controversy about particular points that caused the WG to not adopt the document?

No.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If so, please summarize 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.

4. For protocol documents, are there existing implementations of the contents of the document? Have a significant number of potential implementers indicated plans to implement? Are any existing implementations reported somewhere, either in the document itself (as RFC 7942 recommends) or elsewhere (where)?

Tom Jones reported an implementation in a fork of FreeBSD as the spec was being developed in TSVWG, at IETF 101, London with prototype support for FreeBSD, using RES/REQ exchanges, which at the time were proposed within UDP options. The wire format has not changed since. 
It was also implemented in a scapy, which was used as a test suite during development ([https://github.com/adventureloop/network-tests/tree/master/udpoptions](https://github.com/adventureloop/network-tests/tree/master/udpoptions)).

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other 
  IETF working groups or external organizations, and would it therefore benefit 
  from their review? Have those reviews occurred? If yes, describe which 
  reviews took place.

No.

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

There are no parameters that need review.

7. If the document contains a YANG module, has the final version of the module 
  been checked with any of the [recommended validation tools](https://wiki.ietf.org/group/ops/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 [RFC 8342](https://datatracker.ietf.org/doc/rfc8342/)?

The document doesn't contain a YANG module.

8. Describe reviews and automated checks performed to validate sections of the 
  final version of the document written in a formal language, such as XML code, 
  BNF rules, MIB definitions, CBOR's CDDL, etc.

There are no parameters that need validation.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this 
  document is needed, clearly written, complete, correctly designed, and ready 
  to be handed off to the responsible Area Director?

Yes, the document is needed, clearly written, complete, correctly designed, and ready 
to be handed off to the responsible Area Director.

10. Several IETF Areas have assembled [lists of common issues that their](https://wiki.ietf.org/group/iesg/ExpertTopics) 
    [reviewers encounter](https://wiki.ietf.org/group/iesg/ExpertTopics). For which areas have such issues been identified 
    and addressed? For which does this still need to happen in subsequent 
    reviews?

No common issues were identified or need to be addressed.

11. What type of RFC publication is being requested on the IETF stream ([Best](https://www.rfc-editor.org/rfc/rfc2026.html#section-5) 
    [Current Practice](https://www.rfc-editor.org/rfc/rfc2026.html#section-5), [Proposed Standard, Internet Standard](https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1), 
    [Informational, Experimental or Historic](https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2))? Why is this the proper type 
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

The document is requested to be published as Proposed Standard. This is the proper type for this document since it is generally stable, has resolved known design choices, is believed to be well-understood, has received significant community review, and appears to enjoy enough community interest to be considered valuable. 
The datatracker state correctly reflects this request.

12. Have reasonable efforts been made to remind all authors of the intellectual 
    property rights (IPR) disclosure obligations described in [BCP 79](https://datatracker.ietf.org/doc/bcp79/)? To 
    the best of your knowledge, have all required disclosures been filed? If 
    not, explain why. If yes, summarize any relevant discussion, including links 
    to publicly-available messages when applicable.

The authors were emailed in December 2024, and both of them confirmed that they're not aware of any IPR.

13. Has each author, editor, and contributor shown their willingness to be 
    listed as such? If the total number of authors and editors on the front page 
    is greater than five, please provide a justification.

Both authors have agreed to be listed as such.

14. Document any remaining I-D nits in this document. Simply running the [idnits](https://www.ietf.org/tools/idnits/) 
    [tool](https://www.ietf.org/tools/idnits/) is not enough; please review the ["Content Guidelines" on](https://authors.ietf.org/en/content-guidelines-overview) 
    [authors.ietf.org](https://authors.ietf.org/en/content-guidelines-overview). (Also note that the current idnits tool generates 
    some incorrect warnings; a rewrite is underway.)

Document looks good: [idnits output](https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-tsvwg-udp-options-dplpmtud-13.txt&submitcheck=True&hidetext=True)

15. Should any informative references be normative or vice-versa? See the [IESG](https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/) 
    [Statement on Normative and Informative References](https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/).

Both informative and normative references look correct to me.

16. List any normative references that are not freely available to anyone. Did 
    the community have sufficient access to review any such normative 
    references?

All normative references are freely available.

17. Are there any normative downward references (see [RFC 3967](https://datatracker.ietf.org/doc/rfc3967/) and [BCP](https://www.rfc-editor.org/info/bcp97) 
    [97](https://www.rfc-editor.org/info/bcp97)) that are not already listed in the [DOWNREF registry](https://datatracker.ietf.org/doc/downref/)? If so, 
    list them.

The document doesn't have any downward references.

18. Are there normative references to documents that are not ready to be 
    submitted to the IESG for publication or are otherwise in an unclear state? 
    If so, what is the plan for their completion?

This document references [draft-ietf-tsvwg-udp-options](https://datatracker.ietf.org/doc/draft-ietf-tsvwg-udp-options/), which was recently submitted to the IESG for publication.

19. Will publication of this document change the status of any existing RFCs? If 
    so, does the Datatracker metadata correctly reflect this and are those RFCs 
    listed on the title page, in the abstract, and discussed in the 
    introduction? If not, explain why and point to the part of the document 
    where the relationship of this document to these other RFCs is discussed.

The document doesn't change the status of any existing RFC.

20. 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 aspects of the document requiring IANA assignments are 
    associated with the appropriate reservations in IANA registries. Confirm 
    that any referenced IANA registries have been clearly identified. Confirm 
    that each newly created IANA registry specifies its initial contents, 
    allocations procedures, and a reasonable name (see [RFC 8126](https://datatracker.ietf.org/doc/rfc8126/)).

The document doesn't have any IANA considerations.

21. List any new IANA registries that require Designated Expert Review for 
    future allocations. Are the instructions to the Designated Expert clear? 
    Please include suggestions of designated experts, if appropriate.

No IANA registries are created.

# Shepherd Review \- DPLPMTUD for UDP Options

## Document History

1. Was the document considered in any WG, and if so, why was it not adopted as a work item there?

The document was only considered in TSVWG.

2. Was there controversy about particular points that caused the WG to not adopt the document?

No.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If so, please summarize 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.

4. For protocol documents, are there existing implementations of the contents of the document? Have a significant number of potential implementers indicated plans to implement? Are any existing implementations reported somewhere, either in the document itself (as RFC 7942 recommends) or elsewhere (where)?

Tom Jones reported an implementation in a fork of FreeBSD as the spec was being developed in TSVWG, at IETF 101, London with prototype support for FreeBSD, using RES/REQ exchanges, which at the time were proposed within UDP options. The wire format has not changed since. 
It was also implemented in a scapy, which was used as a test suite during development ([https://github.com/adventureloop/network-tests/tree/master/udpoptions](https://github.com/adventureloop/network-tests/tree/master/udpoptions)).

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other 
  IETF working groups or external organizations, and would it therefore benefit 
  from their review? Have those reviews occurred? If yes, describe which 
  reviews took place.

No.

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

There are no parameters that need review.

7. If the document contains a YANG module, has the final version of the module 
  been checked with any of the [recommended validation tools](https://wiki.ietf.org/group/ops/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 [RFC 8342](https://datatracker.ietf.org/doc/rfc8342/)?

The document doesn't contain a YANG module.

8. Describe reviews and automated checks performed to validate sections of the 
  final version of the document written in a formal language, such as XML code, 
  BNF rules, MIB definitions, CBOR's CDDL, etc.

There are no parameters that need validation.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this 
  document is needed, clearly written, complete, correctly designed, and ready 
  to be handed off to the responsible Area Director?

Yes, the document is needed, clearly written, complete, correctly designed, and ready 
to be handed off to the responsible Area Director.

10. Several IETF Areas have assembled [lists of common issues that their](https://wiki.ietf.org/group/iesg/ExpertTopics) 
    [reviewers encounter](https://wiki.ietf.org/group/iesg/ExpertTopics). For which areas have such issues been identified 
    and addressed? For which does this still need to happen in subsequent 
    reviews?

No common issues were identified or need to be addressed.

11. What type of RFC publication is being requested on the IETF stream ([Best](https://www.rfc-editor.org/rfc/rfc2026.html#section-5) 
    [Current Practice](https://www.rfc-editor.org/rfc/rfc2026.html#section-5), [Proposed Standard, Internet Standard](https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1), 
    [Informational, Experimental or Historic](https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2))? Why is this the proper type 
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

The document is requested to be published as Proposed Standard. This is the proper type for this document since it is generally stable, has resolved known design choices, is believed to be well-understood, has received significant community review, and appears to enjoy enough community interest to be considered valuable. 
The datatracker state correctly reflects this request.

12. Have reasonable efforts been made to remind all authors of the intellectual 
    property rights (IPR) disclosure obligations described in [BCP 79](https://datatracker.ietf.org/doc/bcp79/)? To 
    the best of your knowledge, have all required disclosures been filed? If 
    not, explain why. If yes, summarize any relevant discussion, including links 
    to publicly-available messages when applicable.

The authors were emailed in December 2024, and both of them confirmed that they're not aware of any IPR.

13. Has each author, editor, and contributor shown their willingness to be 
    listed as such? If the total number of authors and editors on the front page 
    is greater than five, please provide a justification.

Both authors have agreed to be listed as such.

14. Document any remaining I-D nits in this document. Simply running the [idnits](https://www.ietf.org/tools/idnits/) 
    [tool](https://www.ietf.org/tools/idnits/) is not enough; please review the ["Content Guidelines" on](https://authors.ietf.org/en/content-guidelines-overview) 
    [authors.ietf.org](https://authors.ietf.org/en/content-guidelines-overview). (Also note that the current idnits tool generates 
    some incorrect warnings; a rewrite is underway.)

Document looks good: [idnits output](https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-tsvwg-udp-options-dplpmtud-13.txt&submitcheck=True&hidetext=True)

15. Should any informative references be normative or vice-versa? See the [IESG](https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/) 
    [Statement on Normative and Informative References](https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/).

Both informative and normative references look correct to me.

16. List any normative references that are not freely available to anyone. Did 
    the community have sufficient access to review any such normative 
    references?

All normative references are freely available.

17. Are there any normative downward references (see [RFC 3967](https://datatracker.ietf.org/doc/rfc3967/) and [BCP](https://www.rfc-editor.org/info/bcp97) 
    [97](https://www.rfc-editor.org/info/bcp97)) that are not already listed in the [DOWNREF registry](https://datatracker.ietf.org/doc/downref/)? If so, 
    list them.

The document doesn't have any downward references.

18. Are there normative references to documents that are not ready to be 
    submitted to the IESG for publication or are otherwise in an unclear state? 
    If so, what is the plan for their completion?

This document references [draft-ietf-tsvwg-udp-options](https://datatracker.ietf.org/doc/draft-ietf-tsvwg-udp-options/), which was recently submitted to the IESG for publication.

19. Will publication of this document change the status of any existing RFCs? If 
    so, does the Datatracker metadata correctly reflect this and are those RFCs 
    listed on the title page, in the abstract, and discussed in the 
    introduction? If not, explain why and point to the part of the document 
    where the relationship of this document to these other RFCs is discussed.

The document doesn't change the status of any existing RFC.

20. 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 aspects of the document requiring IANA assignments are 
    associated with the appropriate reservations in IANA registries. Confirm 
    that any referenced IANA registries have been clearly identified. Confirm 
    that each newly created IANA registry specifies its initial contents, 
    allocations procedures, and a reasonable name (see [RFC 8126](https://datatracker.ietf.org/doc/rfc8126/)).

The document doesn't have any IANA considerations.

21. List any new IANA registries that require Designated Expert Review for 
    future allocations. Are the instructions to the Designated Expert clear? 
    Please include suggestions of designated experts, if appropriate.

No IANA registries are created.

Editor(s), please revise to address all comments you are able, and propose new text on-list for any issues where there is no obvious way forward. Once all issues have been closed, and a new ID is available, the chairs will prepare a write-up requesting publication.

This starts a 3 week WG Last Call call to determine if the following TSVWG IDs are ready to publish:

https://datatracker.ietf.org/doc/draft-ietf-tsvwg-udp-options/

https://datatracker.ietf.org/doc/draft-ietf-tsvwg-udp-options-dplpmtud/

These documents target PROPOSED STANDARD.

The document shepherd  for the UDP Options will be: Gorry Fairhurst.

The document shepherd  for DPLPMTUD with UDP Options will be:  Marten Seemann.

The WGLC will end at midnight UTC on 9th April 2024. 

Please do read the drafts, and send any comments/concerns to the TSVWG mailing list, including notes on whether these are ready to publish (or send an email directly to the chairs ).

Best wishes,

Gorry and Marten

(tsvwg co-chairs)

—

The IETF WG Last Call process is described in RFC 6174.

This document received comments in the WGLC and is returned to the WG for further discussion and progression. A second WGLC is expecte dto be needed to confirm the final text.