Session Date/Time: 23 Jul 2025 09:30

SCHC Working Group Session

Summary

The SCHC working group met to discuss several key technical developments and architectural considerations. Major topics included updates to the SCHC architecture document, Marco's presentation on SCHC for CoAP updates, Alex's discussion of SCHC applicability to interplanetary communications and the chiclets modular approach, Laurent's work on CBOR identifier allocation and management, and two presentations on SCHC applications in 5G networks and geo-networking for autonomous vehicles.

Key Discussion Points

SCHC Architecture Document

The architecture document serves as a living repository of working group consensus rather than a complete specification
Working from implicit LPWAN model to explicit general framework supporting various environments (deep space, PPP, etc.)
Key terminology issues identified:
- Need to replace "SCHC packet" with "SCHC datagram" since SCHC operates on bit streams, not just layer 3 packets
- "SCHC header" term used informally but not formally defined in RFCs
- Proposed terminology: SCHC stratum header vs SCHC payload header vs user payload
New concept of stateless SCHC instances discovered through IEEE 802.15.4 work
Domain concepts needed to define groups of devices that can participate in SCHC instances

SCHC for CoAP Updates (Marco)

Document intended to obsolete RFC 8824 with clarifications and new CoAP option support
Added OSCPIV function for partial IV subfield compression (similar to TKL function)
Updated registry entries sorted by field appearance and option number
Open issue: TKL function needs updating to support RFC 8974 extended tokens
Two open errata being addressed - one approved, one requiring new text as RFC 8724 update
Expected completion in 2-3 more revisions

Protocol Number Allocation (Bob/Pascal)

Need to update document removing UDP port number requests based on TSV ART review feedback
Focus on Ethertype and IP protocol number allocation only
Bob committed to re-engaging on this work

Interplanetary Communications and Chiclets (Alex)

SCHC applicable to TIP-TOP working group needs for deep space communications
Benefits: stateless compression, RTT agnostic, framework maturity
Chiclets concept: modular SCHC sub-functions that interoperate with full implementations
Enables simple specialized implementations (e.g., minimal fixed field compression)
Formal definition allows citing specific functionality subsets

CBOR Identifier Allocation and Management (Laurent)

Received CBOR range allocation: 2505550 with 400 values
Manual allocation more efficient than automatic tools using hierarchy jumps of 23
Question raised about allocating CIDs for soon-to-be-obsoleted values
Core management approach using dedicated management rules and IP stack

5G Integration (Amina)

Placement of SCHC entities: UE and modified UPF (SCHC-UPF)
SCHC signaling integrated into 5G registration and PDU session establishment
PEI (Permanent Equipment Identifier) proposed for device identification
Maintains full IP connectivity between UE and data network

Geo-networking for Autonomous Vehicles (Manosh)

SCHC applied to Cooperative Awareness Messages (CAMs) in vehicular networks
Two rule approaches: conservative (universal) and aggressive (region-specific)
Demonstrated 13% reduction in transmission time and 14% reduction in channel congestion
Architecture challenges for broadcast scenarios and platoon merging

Decisions and Action Items

Bob: Update protocol number document removing UDP port discussion, focus on Ethertype and IP protocol numbers
Marco: Address TKL function for extended tokens in next CoAP document revision
Marco & Laurent: Resolve second erratum through new RFC 8724 update text
Laurent: Proceed with manual CBOR identifier allocation, avoid allocating to obsolete values
Alex: Present SCHC benefits to TIP-TOP working group
Working Group: Continue terminology discussion on mailing list
Working Group: Plan focused terminology sessions for interim meetings

Next Steps

September restart of interim meetings with focused architecture terminology sessions
Continue mailing list discussions on terminology consensus
Marco to publish next CoAP document revision addressing open issues
TIP-TOP working group presentation scheduled for following day
Review and validation of manual CBOR identifier allocation before IANA submission
Consider simulation framework development for SCHC performance evaluation