Session Date/Time: 20 Mar 2026 01:00
The Transport Area Working Group (TSVWG) met at IETF 125 in Shenzhen to discuss a variety of transport-related specifications and operational updates. Key topics included the security of SCTP via DTLS, refinements to the FQ-PIE algorithm, new IPFIX elements for ECN monitoring, and large-scale operational reports on L4S deployment. Significant progress was reported on the DTLS chunk for SCTP, which is nearing Working Group Last Call (WGLC).
Speakers: Zaheduzzaman Sarker, Martin Duke
- Slides: Chairs slides
- One RFC was recently published, and several others are in the RFC Editor queue.
- Milestones: Chairs adjusted milestone dates to provide better predictability for other Standards Development Organizations (SDOs).
- Document Review: A call was made for more cross-sector reviews. draft-ietf-tsvwg-l4sops is currently in Last Call.
- TSV Review Team: Participants were encouraged to join the Transport Area Review Team to assist with IESG reviews.
Speaker: Magnus Westerlund
- Slides: DTLS Chunk for SCTP
- Drafts: draft-ietf-tsvwg-sctp-dtls-chunk, draft-ietf-tsvwg-dtls-chunk-key-management
- Design Update: The design team decided to remove the DTLS Connection ID (CID). SCTP already provides robust demultiplexing via V-tags and port/address pairs, making the CID redundant and adding unnecessary complexity to the API.
- ASCONF Updates: The draft now updates RFC 5061 to specify that the DTLS chunk (rather than SCTP-AUTH) should be used for authenticating address reconfiguration messages.
- Interoperability: Implementation work is ongoing in FreeBSD and Linux. No major technical hurdles remain.
- Key Management: Work on draft-ietf-tsvwg-dtls-chunk-key-management is trailing the main chunk draft to ensure API alignment.
- Targeting WG last call prior to next IETF meeting (IETF-126 Vienna in July).
Speaker: Mohit P. Tahiliani
- Slides: FQ-PIE
- Draft: draft-ietf-tsvwg-fq-pie
- Technical Detail: The draft recommends using the timestamps approach for calculating queue delay rather than Little’s Law.
- L4S Support: Discussion continues on adding L4S support (CE threshold). Mohit P. Tahiliani suggested that a separate draft might be appropriate to define L4S support across all FQ-based mechanisms (FQ-CoDel, FQ-PIE, FQ-Cobalt).
- Implementations: FQ-PIE is supported in the Linux kernel (OpenWrt), FreeBSD, and the ns-3 simulator. Recent work integrated FQ-PIE into go-tc and the work to integrate it in QoSMate is ongoing.
Speaker: Xueyan
- Slides: Export of ECN information in IPFIX
- This individual draft proposes new IPFIX Information Elements (IEs) to monitor L4S traffic (ECT(1), ECT(0), CE, and non-ECT) across IPv4, IPv6, and MPLS.
- Discussion: Gorry Fairhurst questioned why only the 2 ECN bits were being exported instead of the full 8-bit Traffic Class/DSCP field. Xueyan noted that while DSCP IEs exist, specific ECN statistical IEs are needed for L4S visibility.
- Operator Feedback: Jason Livingood expressed strong support, noting that the lack of standardized IPFIX ECN reporting is currently an operational gap for ISPs deploying L4S.
Speaker: Daniel Huang
- Slides: HP-WAN Hackathon report
- Results from a prototype of High-Performance Wide Area Networking (HP-WAN) were presented. The project used RSVP-based signaling for host-to-network coordination to achieve high throughput and low latency.
- Collaboration: Daniel King noted that the hackathon highlighted a need for a consistent "workload model" and a feedback loop from the network to the orchestrator regarding congestion state.
Speaker: Jason Livingood
- Slides: L4S Update - Livingood
- Deployment: Comcast has enabled L4S and NQB for over 10 million homes (approx. 350 million devices). Key use cases include cloud gaming (NVIDIA GeForce NOW, Valve Steam) and real-time communications (FaceTime).
- Technical Challenges:
- FEC Interactions: Jason Livingood noted that existing Forward Error Correction (FEC) algorithms often have baked-in delay assumptions that conflict with the ultra-low latency provided by L4S.
- ECN Bleaching: Stuart Cheshire (Apple) reported instances of ECN bleaching or incorrect CE marking (e.g., in certain mobile networks) which causes throughput degradation.
- Client Status: Stuart Cheshire confirmed that Apple products support Prague (as a modification to Cubic/QUIC) and are currently performing A/B testing in the field.