SCHC

IETF SCHC Working Group Interim Meeting Date: 2026-04 Chair: Laurent Toutain Minutes Secretary: Marco Tiloca

## Summary

The SCHC Working Group held an interim meeting to review the status of active documents, discuss the integration of Forward Error Correction (FEC) mechanisms into fragmentation modes, and provide an update on the progress of the SCHC Architecture. Key focus areas included the refinement of architectural terminology (specifically the "stratum" concept) and the unification of reliability methods for networks prone to disruptions.

## Key Discussion Points

### Working Group Document Status

Laurent Toutain provided an update on the current draft pipeline:

draft-ietf-schc-8824-update: Working Group Last Call (WGLC) concluded on February 10th. Feedback indicated the document is ready, though formal closure is pending. Laurent Toutain will perform a final review and seek a document shepherd.
draft-ietf-schc-protocol-numbers: Currently requires updates to the security section and text regarding UDP port objections. Authors need to submit a revised version.
draft-ietf-schc-over-networks-prone-to-disruptions: The working group is waiting for an updated version to initiate WGLC.
ICMPv6 Compression: The draft is currently expired; authors are requested to submit an update to progress toward WGLC.

### SCHC ARQ-FEC Fragmentation Mode

Javier FERNANDEZ presented an update on the reliability mechanisms for SCHC, specifically focusing on merging concepts into a unified framework for networks with long delays or high error rates.

Slide Deck: SCHC ARQ-FEC Fragmentation Mode draft update Draft Reference: draft-ietf-schc-over-networks-prone-to-disruptions

Mechanism: Proposed a new fragmentation mode called ARQ-FEC. It functions similarly to ACK-on-Error but includes encoding/decoding processes.
Encoding Geometry: Introduced "C-streams" (coded streams) to allow for simpler FEC schemes like XOR, alongside the existing matrix-based structures.
Implementation & Memory: Alexander Pelov and Laurent Toutain raised questions regarding the memory footprint for IoT devices. Javier FERNANDEZ noted that the stream-based approach allows for "on-the-fly" calculations, minimizing memory usage. Rodrigo Munoz-Lara confirmed that the matrix-based solution has been successfully implemented and tested for packet recovery.

### SCHC Architecture Advancement

Laurent Toutain provided a report from the Design Team (including Marion Dumay and Quentin Lampin) regarding the evolution of the SCHC Architecture.

Slide Deck: SCHC Architecture Advancement Draft Reference: draft-ietf-schc-architecture

Core Definitions: The team converged on three pillar definitions:
1. SCHC Instance: The logical component/process executing compression/fragmentation.
2. SCHC Endpoint: The logical peer containing one or more instances.
3. SCHC Session: The communication relationship between instances sharing a common context.
The "Stratum" Concept: A major discussion point was whether to formally introduce the "stratum" to define the scope/layer where SCHC operates.
- Option A (Minimalist): Avoid "stratum" to keep language simple for basic deployments (e.g., draft-ietf-schc-schclet).
- Option B (Rich/Expressive): Use "stratum" to better support complex multi-hop, multi-instance, or dispatching scenarios (e.g., draft-ietf-ipsecme-diet-esp).
Community Feedback:
- Carles Gomez supported the "stratum" term, noting its utility in 6LoWPAN stacks where SCHC might appear in multiple places.
- Edgar Ramos and Marco Tiloca favored the richer language to support the extension of SCHC into new areas.
- Quentin Lampin clarified that the design team is evaluating if a stratum is a functional element with interfaces or merely a descriptive property of an instance.

## Decisions and Action Items

Action (Laurent Toutain): Review draft-ietf-schc-8824-update to formally close the WGLC.
Action (Laurent Toutain): Identify document shepherds for draft-ietf-schc-8824-update, draft-ietf-schc-protocol-numbers, and draft-ietf-schc-over-networks-prone-to-disruptions.
Action (Authors): Update the Security section of draft-ietf-schc-protocol-numbers based on mailing list feedback.
Decision: The WG expressed a preference for "richer language" (Option B) regarding the stratum concept in the architecture draft to ensure long-term extensibility.

## Next Steps

The Design Team will continue iterating on draft-ietf-schc-architecture on GitHub, targeting a 20-40 page informational document with specific use-case annexes.
Authors of the FEC/Reliability work will implement the "stream" solution to provide comparative footprint data.
The next interim meeting will be held in two weeks during the regular slot.

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