SCONE

Summary

The SCONE Working Group met at IETF 120 to discuss the finalization of the core protocol draft, address feedback on the applicability and manageability considerations draft, and plan the future direction of the working group. The group agreed to submit the SCONE protocol draft to the IESG immediately due to external dependencies (such as 3GPP), while continuing to refine the applicability and manageability draft with a target of initiating a Working Group Last Call (WGLC) by early Autumn.

Key Discussion Points

1. Hackathon and Interoperability Status

Marcus Ihlar reported on recent interop experimentation, including testing SCONE advice over emulated satellite links (addressing concerns raised by Gorry Fairhurst regarding highly impaired links).
Work is also ongoing with researchers from the University of Aberdeen to enable open-source adaptive bitrate (ABR) clients to utilize SCONE advice.

2. SCONE Protocol Completion

Martin Thomson confirmed that the draft-ietf-scone-protocol is stable and contains only minor editorial updates since the previous working group last call.
There were no objections to submitting the document to the IESG. The working group agreed to proceed with publication request immediately rather than coupling it with the manageability document, citing deployment urgency from Marcus Ihlar, Matt Joras, and Anoop Prasad (noting 3GPP and real-world deployment timelines).

3. SCONE Applicability & Manageability

Sanjay Mishra presented updates on the SCONE AppMan and Appman Draft for draft-ietf-scone-applicability-manageability.

Version 02 Changes: The draft underwent a significant rewrite. Key changes include moving "Operational Considerations" to the front of the main body, restructuring the introduction, moving per-flow signaling to Section 3, and revising the ECN and L4S interworking sections (distinguishing proactive vs. reactive signaling).
OpsDir Review (Joe Clark):
- PR 55 (detecting when an endpoint ignores advice) was added to address diagnostic capabilities.
- PR 49 (handling non-compliance): Lars Eggert strongly objected to the adversarial language ("penalties", "conformance", "violation") used in the draft, arguing that SCONE is voluntary and non-compliant traffic should simply be treated as best-effort. Gorry Fairhurst agreed that while monitoring is useful for capacity protection, the terminology needs softening. Mirja Kühlewind clarified that rate enforcement is independent of SCONE, and the network will enforce limits regardless of whether an endpoint understands the advice or not. The editors agreed to reformulate the language in the PR.
Tunnels and MASQUE (PR 37):
- Mirja Kühlewind noted the text is generic to tunnels but highlights MASQUE as the prominent QUIC-based case.
- Martin Thomson pointed out an error in the proposed text: clients should not blindly take the minimum of two values across tunnels. Instead, each piece of advice strictly applies only to the specific flow on which it was received.
L4S & Shapers Motivation:
- Stuart Cheshire expressed skepticism regarding the necessity of SCONE over existing traffic shapers, policers, or L4S enforcements, questioning the deployment timelines.
- Martin Thomson and Christian Huitema emphasized that SCONE provides critical rate transparency to endpoints, which is missing from traditional packet-dropping shapers.
Document Reframing:
- Mirja Kühlewind suggested focusing the document purely on operator manageability (possibly dropping "applicability" from the title) and volunteered to submit a PR to reframe the text accordingly.

4. Future of the Working Group & New Work

The working group discussed several proposals for potential rechartering or post-completion work:

SCONE Echo (draft-duke-scone-echo): Martin Duke requested feedback on the draft, specifically regarding its privacy properties. He noted that if SCONE closes, the work could potentially move to the QUIC WG.
SCONE for TCP: Mentioned as a potential item for TCPM or SCONE if rechartered.
RoCE (RDMA over Converged Ethernet) over UDP: A presenter proposed using SCONE-like signaling for wide-area, cross-datacenter RoCE networks to handle slow congestion convergence over long RTTs.
- Lars Eggert questioned how this would interface with RoCE's highly integrated fabric flow control.
- Gorry Fairhurst suggested that this multilayer transport and network interaction is more suited for TSVWG rather than SCONE.
Chairs' Guidance: Brian Trammell stated that the working group will remain open to process the core documents. Proponents of new work (including SCONE TCP, Echo, and RoCE) must mature their proposals and have drafts ready for a formal rechartering discussion at IETF 121 (San Francisco).

Decisions and Action Items

Action Item: Brian Trammell to submit draft-ietf-scone-protocol to the AD/IESG for publication.
Action Item: Mirja Kühlewind to submit a PR reframing draft-ietf-scone-applicability-manageability to focus more exclusively on operator manageability advice.
Decision: The working group will not couple the progression of the protocol and manageability drafts; the protocol draft will proceed immediately.
Action Item: Working group participants must submit any new PRs or major comments on draft-ietf-scone-applicability-manageability by August 12.

Next Steps

Editors to resolve open GitHub PRs and issues for draft-ietf-scone-applicability-manageability throughout August.
Target a Working Group Last Call (WGLC) for the manageability draft by mid-September to early October.
Proponents of new work items to foster discussion on the mailing list ahead of the rechartering evaluation at IETF 121.

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