DETNET - IETF 125 Meeting Minutes

Session: DETNET
Chairs: János Farkas, Lou Berger
Secretary: Eve Schooler
Location: Shenzhen & Remote

Summary

The DetNet working group session at IETF 125 focused on the progression of recently adopted queuing mechanisms, enhancements to the data plane taxonomy regarding interoperability, and new proposals for SRv6 and multi-domain control plane frameworks. Significant discussion occurred regarding the relationship between DetNet drafts and ITU-T standards, the potential merging of similar queuing mechanisms, and the requirements for flow aggregation.

Key Discussion Points

1. WG Status and Introduction

Presenters: János Farkas, Lou Berger
Slides: 01) Title: Intro, WG Status, Draft Status
Highlights:
- One new RFC published: DetNet Controller Plane.
- RAW technologies and architecture drafts are in the RFC editor queue.
- Several queuing solutions were recently adopted.
- A liaison was received from ITU-T SG13 regarding deterministic networking results.

2. Dataplane Enhancement Taxonomy

Presenter: Jinu Jung
Draft: draft-ietf-detnet-dataplane-taxonomy
Slides: 02) Dataplane Enhancement Taxonomy
Discussion: Focused on the new Section 8 regarding interoperability between technology domains (TD). Introduced metrics: Gateway Complexity (GC) and Performance Preservation Level (PPL). Discussions highlighted the difficulty of slot length negotiation and the trade-offs of flow reshaping/damping.

3. Latency Guarantee with Stateless Fair Queuing (CS-Core)

Presenter: Jinu Jung
Draft: draft-joung-detnet-stateless-fair-queuing (Note: Adoption in progress)
Slides: 03) Latency Guarantee with Stateless Fair Queuing
Discussion: Jinu Jung reported updates to header formats (IPv6 Hop-by-Hop and MPLS MNA) and admission control.
- ITU-T Relationship: Lou Berger and Mike McBride emphasized the need to remove duplicative parts and ensure no conflicts with existing ITU standards.
- Action: The authors will issue a revision removing duplicates to finalize the transition to a working group document.

4. Non-Work Conserving Stateless Core Fair Queuing (N-Score)

Presenter: Yeon-cheol Ryu
Draft: draft-ietf-detnet-nscore
Slides: 04) On-time Forwarding with Non-Work Conserving Stateless Core Fair Queuing
Discussion: Updated to clarify packet handling (temporary queue vs. service queue). Shaofu Peng questioned the damping buffer design. Authors confirmed N-Score maintains no per-flow state and is being implemented on FPGA.

5. Push-In First-Out (PIFO) Queue

Presenter: Yeon-cheol Ryu
Draft: draft-ietf-detnet-ontime-forwarding
Slides: 05) On-time Forwarding with Push-In First-Out (PIFO) queue
Discussion: Shaofu Peng raised concerns about guaranteeing packet scheduling before maximum departure time. Authors plan to add mathematical formulas for admission control in the next version.

6. Deadline Based Deterministic Forwarding

Presenter: Shaofu Peng
Draft: draft-ietf-detnet-deadline-based-forwarding
Slides: 06) Deadline Based Deterministic Forwarding
Discussion: Removed stateful options (1 and 2) to maintain scalability. The draft now focuses on stateless options (3 and 4).

7. Timeslot Queueing and Forwarding (TQF) and TCQF

Presenter: Shaofu Peng
Drafts: draft-ietf-detnet-packet-timeslot-mechanism (TQF) and draft-ietf-detnet-tcqf (TCQF)
Discussion: The chairs suggested merging TQF and TCQF due to similarities.
- Contention: Toerless Eckert argued that TCQF is class-based and simple for high-speed hardware, whereas TQF is more flow-based/per-hop. Yi Zhao preferred keeping them separate to maintain the simplicity of TCQF.
- Scalability: Jinu Jung questioned the scalability of per-flow, per-hop slot scheduling.

8. Flow Aggregation and Data Fields

Presenter: Shaofu Peng
Slides: 08) Flow Aggregation for Enhanced DetNet and 09) Data Fields for DetNet Enhanced Data Plane
Discussion: Balazs Varga questioned the need for new flow aggregation methods, suggesting existing data plane documents already cover this. Chairs recommended reframing the aggregation draft as a "Framework" rather than a specification. Regarding Data Fields, the chairs suggested the queuing solutions must mature before a common metadata format can be standardized.

9. Enhanced Data Plane (EDP) Interoperation

Presenter: Shaofu Peng
Slides: 10) DetNet EDP Interoperation
Discussion: Proposed using "common metadata" (e.g., latency deviation) and "differentiated metadata" (solution-specific like cycles or finish times). Jinu Jung expressed doubt that a universal "common metadata" exists across all DetNet categories.

10. SRv6 Data Plane

Presenter: Balazs Varga
Slides: 13) Deterministic Networking SRv6 Data Plane
Discussion: The draft leverages SRv6 Redundancy SIDs for packet replication and elimination. Coordination with the SPRING WG is required.
Polls:
- Interest in the topic: Strong support.
- Suitable as WG foundation: Strong support.

11. Multi-Domain Control Plane Framework

Presenter: Carlos Bernardos
Slides: 14) A Control Plane Framework for Multi-Domain Deterministic Networking (DetNet)
Discussion: The framework is now technology-agnostic (moving away from PCEP-only). It defines control domains and functional requirements for multi-domain coordination. Toerless Eckert supported a "minimum possible RFC" to promote inter-domain DetNet.
Polls:
- Interest in the topic: Strong support.
- Suitable as WG foundation: Strong support (with some technical objections to be addressed on the list).

Decisions and Action Items

CS-Core Draft: Authors to remove duplicative ITU-T content. WG to move toward formal adoption as draft-ietf-detnet.
TQF/TCQF: Authors of both drafts to continue discussions on the mailing list regarding a potential merge or better clarification of distinct use cases.
Flow Aggregation: Authors to revise the document to be a "Framework" and clarify its relationship with existing data plane formats.
Metadata: Work on common data fields will be deferred until individual queuing drafts are more stable.

Next Steps

SRv6 Data Plane: Chairs will coordinate with SPRING WG chairs before initiating an official adoption poll.
Multi-Domain Framework: Chairs will initiate an adoption poll on the mailing list.
General: Authors of newly adopted queuing drafts (N-Score, PIFO, Deadline, TQF) to address technical issues raised during adoption calls in their next revisions.

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