Markdown Version | Session Recording

Session Date/Time: 25 Jul 2023 22:00

CCWG Meeting Minutes

Summary

The first meeting of the Congestion Control Working Group (CCWG) covered a variety of topics including a recap of the working group charter, discussions surrounding the revision of RFC5033 ("5033bis"), an analysis of differences between standard congestion control schemes, an update on BBRv3 deployment at Google, congestion control for DCCP, and a new approach to congestion control using inbound telemetry. The meeting involved active participation from attendees, with a focus on defining the scope of the working group's activities and prioritizing future work.

Key Discussion Points

• Charter Review:
  • The CCWG charter focuses on congestion control, applicable to all transport protocols, not just TCP.
  • The working group is looking for proposals with empirical evidence of safety and stated intent to deploy.
  • Coordination with other working groups (e.g., ICCRG, TCPM) is a priority.
• RFC5033bis:
  • Discussion on whether to adopt the existing 5033bis draft as the starting point or start from scratch.
  • Concerns were raised about recommendations in RFC5843 having negative effects.
  • Authorship of the document was discussed, with a proposal to remove Sally Floyd and Mark Allman as authors.
  • The scope of 5033bis was debated, specifically whether to address multipath congestion control.
  • A discussion about the definition of "fairness" within the context of congestion control, with suggestions to focus on "freedom from starvation" instead.
• Analysis of Congestion Control Schemes:
  • A presentation comparing various congestion control standards, including TCP Reno, QUIC Reno, and Cubic.
  • Differences in initial window sizes, minimum RTO, and loss window were highlighted.
  • It was suggested that 5681 should be updated to align with 9002.
• BCP41 Update:
  • Discussion about updating or replacing BCP41 (principles of congestion control).
  • A key proposal was to differentiate between congestion and persistent congestion.
  • A suggestion was made to replace the term "congestion control" with "rate optimizer."
• BBRv3 Update:
  • An update on bug fixes and performance tuning in BBRv3.
  • Deployment status at Google was discussed.
  • BBRv3 is open-sourced and plans to merge it into the mainline Linux kernel.
  • Fixes to bandwidth convergence problems.
• Congestion Control for DCCP:
  • Existing CCID profiles for DCCP are based on TCP.
  • Discussion on the potential for adding CCID profiles for Cubic and BBR.
  • New CCID profiles need to be standard-track, which is a TSBWG matter.
• Congestion Control Using Inbound Telemetry:
  • A new approach to congestion control using inbound telemetry from network ASICs.
  • The use of IOAM, INT, and IFA for telemetry was mentioned.
  • The importance of action time, especially in data center environments, was emphasized.

Decisions and Action Items

• Adopt 5033bis: The working group agreed to adopt the existing 5033bis draft as the starting point for revision.
• Remove Authors: Sally Floyd and Mark Allman will be acknowledged but no longer listed as authors of 5033bis.
• BBRv3 in Linux: Google plans to submit BBRv3 patches for inclusion in the mainline Linux kernel.
• DCCP and TSBWG: Nathalie Romo will need to submit the DCCP CCD profile drafts for review by TSBWG.

Next Steps

• Corey and Mathis will continue editing the 5033bis draft.
• Attendees are encouraged to review and provide feedback on the 5033bis, BCP41 Update, and Inbound Telemetry drafts on GitHub.
• Explore options for new drafts on transport prognostic renal congestion control.
• Further discussion on the scope and relationship between 5033bis and a potential update to BCP41.