[Detnet] Re: New Liaison Statement, "LS on deterministic networking work of draft Recommendation ITU-T Y.qos-sre-rf in Q6/WP4 of ITU-T SG13"

[Scott Mansfield <[e-mail]>]

A liaison from the IETF to SG13 may provide information on changes made to an IETF Internet-Draft and may, if appropriate, identify the SG13 documents that could be affected by those changes. The liaison may also indicate which SG13 documents informed or motivated the changes incorporated into the Internet-Draft.

Because both the IETF and ITU-T operate through contribution-driven processes, it would not be appropriate for the IETF to use a liaison statement to direct or prescribe modifications to an ITU-T Recommendation based on changes made elsewhere. A liaison may identify a potential inconsistency or highlight an issue for consideration, but any resulting modifications to ITU-T texts would need to be proposed and advanced through contributions submitted by ITU-T members in accordance with ITU-T procedures.

Based on the notes below I think what the IETF could say is: (If I understand the nuance of Jinoo’s points)…

The IETF DETNET Working Group is aware of the work in ITU-T Y.qos-sre-rf. In support of maintaining consistency between IETF and ITU-T specifications, draft-ietf-detnet-stateless-fair-queuing relies on concepts defined in ITU-T Recommendations Y.3129 and Y.3148. The IETF would welcome information on any significant updates to Y.3129 and Y.3148 as work on those Recommendations progresses.

-scott.

From: Jinoo Joung <[e-mail]>
Sent: Wednesday, September 16, 2026 9:26 PM
To: Mike Blanche <[e-mail]>
Cc: Deterministic Networking Discussion List <[e-mail]>; Janos Farkas <[e-mail]>; Lou Berger <[e-mail]>
Subject: [Detnet] Re: New Liaison Statement, "LS on deterministic networking work of draft Recommendation ITU-T Y.qos-sre-rf in Q6/WP4 of ITU-T SG13"

Dear Chairs, Mike, and WG,

As it was discussed during the meeting and the offline chat after the meeting,
the standards produced in both SDOs should remain consistent and non-overlapping.
This is what we have agreed upon.

I think it would be helpful to send a liaison to ITU-T SG13 to suggest that;
- ITU-T Y.3129 and Y.3148 should be revised accordingly to reflect the addition of the medata that is being suggested by ITU-T Y.qos-sre-rf.
- draft-ietf-detnet-stateless-fair-queuing should develop the MPLS and IPv6 header format in-line with the framework specified by Y.3129 and Y.3148.

Best regards,
Jinoo



On Thu, Aug 6, 2026 at 8:58 PM Mike Blanche <[e-mail]<mailto:[e-mail]>> wrote:
(trimming to the detnet wg)

Hello Detnet WG, chairs,

Catching up after Vienna - thank you for sharing this liaison from ITU-T SG13.

From Jinoo's presentation<https://datatracker.ietf.org/meeting/126/materials/slides-126-detnet-03-latency-guarantee-with-stateless-fair-queuing-00> at IETF 126, I think the proposed solution to the issue identified in this liaison is to amend draft-ietf-detnet-stateless-fair-queuing so it uses four metadata fields instead of three. This then creates a challenge back in ITU-T SG13 because Y.3129 and Y.3148 refer to three metadata fields not four.

Jinoo's presentation says these ITU-T standards will now be revised, but I suggest mentioning this in the return liaison, as changing the IETF draft triggers a need for such revisions to maintain consistency.

It was great that the Q6/13 rapporteur could attend the detnet session in Vienna and meet with the chairs afterward. I encourage a continued conversation between the chairs and the two groups more broadly, as suggested in the liaison.

If the chairs would like specific suggested wording for the liaison response, please let me know.



Beyond the specific response to this liaison, I remain concerned that some of this work is still evolving, making standardisation potentially premature. The ongoing discussion about encoding the required metadata illustrates this point:

1) Y.3129 ("Requirements and framework for stateless fair queueing") was consented in April 2024 with 3 metadata fields.
2) Y.3148 ("Functional architecture for stateless fair queuing in large scale networks including IMT-2020 and beyond") initially included only 2 metadata fields, described as an optimisation. When it was being finalised in April 2025, following discussion, this was then changed to 3 fields to be consistent with Y.3129 and consented as such.
3) when adopting draft-joung-detnet-stateless-fair-queuing in March 2026, the unadopted I-D also used 2 pieces of metadata, and we discussed making it consistent with the two published ITU-T standards above. The initial proposal on the mailing list (here<https://mailarchive.ietf.org/arch/msg/detnet/Z6kwG_bScD8TrUMunulcVDwHyTs/>) was for the draft to support 2 or 3 pieces of metadata. After IETF 125 and further discussion, the draft was adopted using 3 metadata fields.
4) Back in SG13, a further related draft standard Y.qos-sre-rf is coming up for consent, but it has 4 pieces of metadata, generating this liaison.
5) The proposal made at IETF 126 is to modify draft-ietf-detnet-stateless-fair-queuing, Y.3129 and Y.3148 to use 4 pieces of metadata. I understand this is the final proposed revision!

The resulting need for ongoing amendment of drafts and published standards across multiple SDOs seems inefficient. I hope we have settled on a consistent, forward-looking set of metadata necessary to implement these algorithms (and any future related work) without further changes to existing standards.

Feedback from implementers using these architectures in the wild would be very useful input.

Many thanks,

Mike

On Tue, 21 Jul 2026 at 07:13, Liaison Statement Management Tool <[e-mail]<mailto:[e-mail]>> wrote:
Title: LS on deterministic networking work of draft Recommendation ITU-T Y.qos-sre-rf in Q6/WP4 of ITU-T SG13
Submission Date: 2026-07-20
URL of the IETF Web page: https://datatracker.ietf.org/liaison/2204/

To: Deterministic Networking (detnet)
From: ITU-T SG 13
Purpose: For action
Please reply by 2026-09-30

Email Addresses
---------------
From: [e-mail]<mailto:[e-mail]>
To: Lou Berger <[e-mail]<mailto:[e-mail]>>,János Farkas <[e-mail]<mailto:[e-mail]>>
Cc: Jim Guichard <[e-mail]<mailto:[e-mail]>>,Deterministic Networking Discussion List <[e-mail]<mailto:[e-mail]>>,Lou Berger <[e-mail]<mailto:[e-mail]>>,Scott Mansfield <[e-mail]<mailto:[e-mail]>>,Ketan Talaulikar <[e-mail]<mailto:[e-mail]>>,János Farkas <[e-mail]<mailto:[e-mail]>>,Gunter Van de Velde <[e-mail]<mailto:[e-mail]>>
Response Contacts: [e-mail]<mailto:[e-mail]>
[e-mail]<mailto:[e-mail]>
Technical Contacts: [e-mail]<mailto:[e-mail]>


Body: 1. Purpose

The purpose of this liaison statement is to inform the IETF DetNet Working Group about the maturity of draft Recommendation ITU-T Y.qos-sre-rf, which is currently being prepared for consent in SG13 for our October 2026 Plenary meeting, and to seek feedback to ensure alignment with ongoing IETF draft standards.

2. Discussion and Context

ITU-T Q6/13 has been progressing work on deterministic networking and stateless mechanisms. Recommendation ITU-T Y.3129 "Requirements and framework for stateless fair queuing in large scale networks including IMT-2020 and beyond", utilises three pieces of metadata carried within packet headers to execute stateless fair queuing in core nodes:

a) The packet's Finish Time
b) The flow's allocated service rate
c) The maximum packet size of the flow

We acknowledge and highly value the parallel work occurring within the IETF DetNet WG,  in particular via draft-ietf-detnet-stateless-fair-queuing, which specifies the mechanisms to encapsulate these three fields into IPv6 and MPLS.

3. Y.qos-sre-rf Fourth Metadata Field

The new draft Recommendation ITU-T Y.qos-sre-rf extends this capability into the control plane for stateless admission control. To identify the total service rates of active flows on a link without maintaining per-flow state tables, the framework introduces a fourth metadata field:

d) Finish Time Difference: Defined as the difference between the current packet’s finish time and the previous packet’s finish time

Because this remains constant across all nodes in the path, core nodes can use it alongside the existing Y.3129 metadata to determine whether an arriving packet "encompasses" a given estimation reference time. This allows the node to mathematically infer active flow rates during an inspection interval without managing flow states.

4. Request for Feedback

As the IETF DetNet WG is actively developing the IPv6 and MPLS encapsulation for stateless fair queuing, Q6/13 respectfully requests that the IETF DetNet WG review this draft new Recommendation and provide feedback from an IETF perspective, particularly regarding its relationship with draft-ietf-detnet-stateless-fair-queuing.

We would highly appreciate your response before our next SG13 Plenary meeting, scheduled for October 2026.

5. Future Collaboration

More broadly, Q6/13 recognizes that closer collaboration between our organisations would benefit the development of deterministic networking. We welcome the opportunity for enhanced collaboration, including the potential for joint or co-located meetings in future cycles. In addition to this Liaison, the Rapporteur of Q6/13 will reach out informally to the IETF DetNet WG Chairs to discuss potential areas for cooperation.
Attachments:

    Draft Recommendation ITU-T Y.qos-sre-rf: “Requirements and framework for service rates estimation with packet metadata for stateless admission control”
    https://www.ietf.org/lib/dt/documents/LIAISON/liaison-2026-07-21-itu-t-sg-13-detnet-ls-on-deterministic-networking-work-of-draft-recommendation-itu-t-yqos-sre-rf-in-q6wp4-of-itu-t-sg13-attachment-1.pdf


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