Session Date/Time: 21 Oct 2022 15:00

MOQ

Summary

The first MOQ Working Group interim meeting covered administrative topics, logistics for collaboration tools, the path forward for the use cases and requirements document, and an initial discussion on key technical questions derived from the working group charter. Decisions were made regarding GitHub usage, and a plan was established for investigating a real-time communication tool with archival properties. Authors presented their plans for new and updated drafts ahead of the IETF 115 meeting in London, with an emphasis on a unified protocol approach.

Key Discussion Points

Administrative Items:
- James was secured as the primary note-taker, with assistance from Cullen.
- The Note Well was read, reminding participants of IETF policies regarding anti-harassment, code of conduct, copyright, and patent policies.
- The agenda was accepted without modification.
GitHub Usage:
- The working group discussed the modes of operation outlined in RFC 8874, specifically regarding issue tracking versus issue discussion.
- There was strong sentiment in favor of using GitHub.
- Spencer and Victor advocated for using GitHub for issue tracking, with discussion and confirmation happening on the mailing list. They noted this approach has been successful in other working groups like QUIC and WebTransport.
- The chair clarified that the mailing list remains the definitive forum for confirming all working group decisions, per IETF process.
Real-time Communication Tool (e.g., Slack):
- The chair noted that no IETF document governs Slack usage and highlighted the historical limitations of the free Slack client for archival purposes.
- Victor suggested using Slack for interop and implementation discussions, but not for design decisions, citing searchability and archival issues.
- Cullen strongly objected to any tool that does not ensure 100% long-term public archiving, due to legal and patent considerations, suggesting mirroring to an email list. He also expressed concerns about Zulip's usability and noted that groups often conduct design discussions on informal tools despite stated intentions.
- Spencer mentioned IETF's potential future direction towards Zulip.
- Suhas reiterated the need for archiving if an informal tool is used, to capture any inadvertent design discussions.
- Alan (speaking informally) pointed out an existing, informal MOQ channel within the QUIC Dev Slack for author coordination and offered to share a link.
- The chairs proposed not making an immediate "yes/no" decision on Slack. Instead, they would investigate using Zulip (an IETF-supported tool with archival properties) or finding a mechanism to archive Slack messages, with the understanding that any such tool would be for informal communications only, but its content would be retained.
- A call for volunteers to investigate Slack archiving methods received no responses.
Use Cases and Requirements Document:
- Spencer and James presented their individual draft as a potential starting point for the working group's use cases and requirements document.
- They proposed revising the draft to align with the approved MOQ charter, removing historical observations and author opinions, and developing an initial structure for requirements based on the charter.
- Questions were posed to the working group:
  1. Are there other use cases in scope for MOQ with unique requirements beyond live streaming, gaming, and media conferencing (e.g., the "Hybrid" use case from section 4.2 of their draft)?
  2. Is there sufficient descriptive material in the current draft's use case section to explain the derived requirements?
- Cullen supported the proposed path, suggesting that non-agreed points in the draft should be clearly identified as such to facilitate working group discussion.
- James clarified that adopting the document means it serves as a reasonable basis for working group work, and any controversial points can be addressed through consensus post-adoption.
- Spencer inquired about immediate adoption, but the chairs deferred the call for adoption to the mailing list or IETF 115, following document revision.
Key Technical Questions to Tackle (Presentation by Suhas):
- Suhas presented a comprehensive list of technical questions derived from the charter, intended to guide the working group's initial tasks and protocol design.
- Core areas: A common publication protocol (between ingest/distribution), naming/addressing conventions, media packaging, and end-to-end security considerations.
- Specific points included: Media type/quality specification, unique identification, media granularity (frames/GOPs), metadata for relays (priority, dependencies, caching), mapping to QUIC streams/datagrams, transport mechanisms (WebTransport, HTTP/3), application domain scope for naming, existing packaging formats (CMAF), consumer request mechanisms, relay responsibilities (caching, pipelining, metadata-driven decisions), and end-to-end encryption options (DRM, MLS/SFrame).
- Discussion on Prioritization:
  - Spencer suggested prioritizing a clear specification of the protocol stack and considering existing business models. He also suggested a GitHub Wiki for tracking the backlog of technical questions.
  - Luke emphasized the importance of correctly handling media transport and specifically, how to drop media during congestion in an encoding-aware manner.
  - Mo reinforced the urgency of addressing media packaging as it quickly highlights differing assumptions and is critical for transport.
  - Will stressed the need to design the protocol from the outset to scale over intermediaries (relays), rather than focusing solely on client-server communication.
  - There was a sense of the room to prioritize discussions around the common media publication protocol, media packaging, and designing for intermediaries/relays, particularly how to manage media drops under congestion.
Upcoming Drafts and London Presentations:
- The draft submission deadline for IETF 115 is Monday.
- Spencer and James are revising their use case document.
- Renjie (on phone) indicated a submission on MOQ analysis with relays as first-class citizens.
- Maxim plans to submit a draft on estimating live streaming metrics (jitter, packet loss); the chairs suggested mailing list discussion first, given its potentially broad applicability.
- Xavier plans to submit a draft on relay types at 5G/wireless network ingress points, focusing on congestion/energy saving and required metadata.
- Luke provided a preview of a "unified draft" aiming to combine elements from QuickR, Rush, and Warp. The goal is to establish a single approach for media delivery, particularly addressing how to drop media during congestion while respecting encoding dependencies (e.g., I, P, B-frames). The unified draft aims for flexibility, allowing a stream for any number of frames, with a header containing dependency information for relays. A key question for the WG is how CDNs will support such a pub/sub model versus traditional pull-based systems. Luke acknowledged the collaborative effort behind this draft and shared a link to the current draft and GitHub repository on the mailing list.
- Spencer commended the authors on finding common ground for the unified draft and stressed the importance of early, broad review by relevant experts (e.g., YouTube, CDNs, video codec community).

Decisions and Action Items

Decision: The MOQ Working Group will use GitHub for issue tracking, with all working group decisions confirmed on the mailing list.
- Action Item: Chairs to communicate this decision to the mailing list for formal confirmation.
Action Item: Chairs to confirm the IETF's direction and support for Zulip with the IETF tools team.
Action Item: Chairs to investigate mechanisms for archiving real-time communication tools (e.g., Slack to an archival medium or using Zulip), prioritizing the archival property for even informal communications.
Action Item: Spencer and James to revise their use cases and requirements draft to reflect the approved MOQ charter, removing out-of-scope content and clearly identifying non-consensus points.
Action Item: Chairs to find a suitable home (e.g., GitHub Wiki) to track the backlog of technical questions identified in Suhas's presentation and the subsequent discussion.
Action Item: Chairs to review newly submitted drafts (Renjie, Xavier, Luke's unified draft) to integrate them into the IETF 115 London agenda as appropriate.

Next Steps

Working group participants are encouraged to review the current iteration of Luke's "unified draft" (combining QuickR, Rush, and Warp efforts) on GitHub and provide feedback on the mailing list.
Authors of all drafts (including Spencer and James's use cases document, Renjie's relay analysis, Xavier's 5G/wireless relay draft, and Luke's unified draft) are expected to submit their latest revisions by the IETF 115 deadline.
Continued discussion on the identified key technical questions (media packaging, congestion management, relay design, common publication protocol) will proceed on the mailing list.
Prepare for IETF 115 in London, where these topics and draft proposals will be discussed in more technical detail.