Cc’ing 6lo.

The VOICI draft mentioned below is available here: 
https://datatracker.ietf.org/doc/draft-lampin-voici/.
Unfortunately the revised architecture document has not yet been published, but 
hopefully it will be ready soon.
Feel free to contact us for further clarification or to ask any questions.

Best regards,

Alex, Marion & Quentin

From: [email protected] <[email protected]>
Date: Tuesday, 30 June 2026 at 18:10
To: Carles Gomez Montenegro <[email protected]>; lp-wan <[email protected]>; 
schc <[email protected]>; Ana Minaburo <[email protected]>
Subject: [lp-wan] VOICI as SCHC Control Header for 6Lo — invitation to discuss

Hi Carles, Ana, and WG,

We've been working on the revised SCHC architecture document and mapping its 
terminology (Endpoint, Instance, Discriminator, Dispatcher) to the concepts in 
draft-ietf-6lo-schc-15dot4.
The 6Lo draft provides a really interesting deployment scenario to stress-test 
the architecture, and we would appreciate your feedback.

We think that VOICI (draft-lampin-voici) would be a good candidate to serve as  
the SCHC Control Header for 802.15.4 deployments. Here is the reasoning.

The key idea is simple. The architecture document defines the SCHC Control 
Header as an optional header that carries routing metadata whenever the 
extrinsic Discriminator isn't enough.
When an Endpoint runs more than one Instance (the "Multiple-end point" case in 
the 6Lo draft), the dispatcher needs an explicit value to route each Datagram 
to the correct Instance.

One possibility is that VOICI embodies the Control Header:

  - The SCHC Dispatch byte signals the presence of a VOICI header
  - The VOICI Session ID identifies the target Instance
  - Minimal overhead: 1 byte in the common case (3-bit inline Session ID), 
LEB128 extension for larger spaces
  - Optional integrity (CRC-16) and original framing recovery come along "for 
free"
  - For the Single-end point case (one Instance per Endpoint), VOICI is absent 
— the SCHC Dispatch byte alone serves as the extrinsic Discriminator

For the Single-end point case, no change at all.  For Multiple-end point, the 
VOICI header *is* the Control Header on the wire — the Session ID provides the 
Discriminator value the Dispatcher needs.

We're interested to know:

  - Does this cover all the multiplexing scenarios in the 6Lo draft?
  - Are there corner cases, especially around multihop (SRO, TRO, PRO,  
Mesh-Under), that VOICI doesn't address?
  - Is the 1-byte overhead acceptable, or does the compressed Control Header 
provide a meaningfully smaller option?

We're happy to arrange a side meeting or call to talk through this. The 6Lo 
deployment is exactly the kind of scenario the architecture document needs to 
illustrate, and your feedback would be very welcome.

Thanks,

Alex, Marion & Quentin



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