**Session Date/Time:** 23 Jul 2025 12:30

# tsvwg

## Summary
This TSVWG meeting covered several topics including updates on working group document status, discussions on L4S deployment and fairness, updates on the KEFresume Q log draft, and experiences with L4S in production environments. The meeting also included a discussion on the challenges of transitioning away from older standards and the complexities of balancing performance and fairness in congestion control. Finally there was a discussion of a deployment document for low latency.

## Key Discussion Points
*   **Working Group Document Status:** Updates were provided on documents in the RFC editor queue, with the IESG, and those nearing working group last call.
*   **KEFresume Q log Draft:** Awaiting dependency resolution on other Q-log drafts for publication. Discussion of need for expert review from the Quick working group.
*   **L4S Fairness:** Discussion on the imbalance between L4S and classic congestion control, and the need for fairness. Alternatives such as flow queuing were discussed.
*   **L4S Deployment (Comcast):** Jason Livingood provided an update on Comcast's L4S deployment, reaching 7.5 million homes.
*   **L4S Real World Testing (Apple):** Stuart Cheshire presented promising results on L4S performance in Apple's network quality tool and FaceTime, highlighting reduced latency and improved user experience, L4S is currently deployed in the current public beta of iOS and macOS.
*   **Low Latency Deployment Draft:** The charter and relevancy of this deployment focused draft in relation to the working group.
*   **Linux Kernel:** Updates on patch status that include Accurate ECN, TCP and DualPiQ were presented.

## Decisions and Action Items
*   **L4S Ops Draft:** The group appeared in favor of publishing as an informational RFC. Authors to consider if they want to include an appendix with configuration guidance or a link to an external wiki.

## Next Steps
*   The working group will continue monitoring the progress of the Q-log drafts and the KEFresume Q log draft.
*   Chairs will coordinate with Quick working group to get an expert reviewer for KEFresume Q log draft.
*   The L4S Ops draft will likely be submitted for working group last call.
*   Discussion will continue after the break with Mohit's FQ Pi discussion and then all the SCTP.


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**Session Date/Time:** 23 Jul 2025 14:00

# tsvwg Meeting Minutes

## Summary

This meeting covered two main topics: an update on the FlowCube (FQPi) draft and a presentation on the DTLS over SCTP solution developed by a design team. The FQPi draft aims to standardize the FlowQueue-PI algorithm and initial feedback suggested readiness for adoption.  The DTLS over SCTP presentation detailed the proposed architecture and key management, aiming for a compromise between different approaches. Both the DTLS chunk and key management documents were received favorably for adoption as working group items.

## Key Discussion Points

*   **FQPi Draft:**
    *   The draft combines flow queuing with the PI algorithm, similar to FQ-CoDel, with a timestamp-based modification for queue delay calculation.
    *   Three implementations exist: Linux, FreeBSD, and NS3.
    *   The draft addresses a specification gap for FQPy compared to CoDel, FQ-CoDel and PI.
    *   The draft includes information on testing and deployment.
    *   Concern raised about potential impact of using timestamps to determine AQM action. The response addressed the Linux kernel implementation, which uses sojourn time calculation.
*   **DTLS over SCTP:**
    *   The proposed architecture includes a DTLS record protector and a DTLS chunk protector, functionally equivalent but with different payloads and parameters.
    *   Key management utilizes DTLS 1.3 with post-handshake authentication and TLS extended key update.
    *   The DTLS chunk aims to reuse existing record processing implementations.
    *   A new mechanism for downgrade protection is included, using protection solution indicators in key derivation.
    *   The DTLS chunk header is encrypted but not the SCTP common header.
    *   SCTP restart is supported using specific restart key material generated during the DTLS connection setup.
    *   Dependency on ongoing work in the TLS working group regarding extended key update.
    *   Discussion of IPR declaration and its impact on implementation.
    *   Presentation of the DTLS chunk and key management API.

## Decisions and Action Items

*   **FQPi Draft:**
    *   The working group agreed to proceed with an adoption call on the mailing list.
*   **DTLS over SCTP:**
    *   The working group agreed to adopt both the DTLS chunk and the key management documents as working group items, pending confirmation on the mailing list.
    *   **Action Item:** Proponents (Magnus Westlund and Michael Tuexen) to draft a liaison statement to 3GPP, describing the progress and outlining the two documents, dependencies, and expected timeline.
    *   **Action Item:** Charles Eckel to handle liaisoning with the TLS working group regarding the extended key update draft.
    *   **Action Item:** Proponents to determine appropriate milestones for both documents.

## Next Steps

*   Confirmation of adoption for FQPi draft and DTLS over SCTP documents via the mailing list.
*   Drafting and sending the liaison statement to 3GPP.
*   Progressing the DTLS chunk document independent of the key management document, if possible.
*   Continued monitoring of the TLS working group's progress on the extended key update draft.