Subject: [lp-wan] draft-ietf-lpwan-coap-static-context-hc-14.txt and Magnus Westerlund Discuss

From: Magnus Westerlund <[email-masked]>
Date: Thu, 28 May 2020 15:32:37 +0000

Hi,

I have looked at the changes in the latest version. However, I don't think they
resolve my discuss (
https://datatracker.ietf.org/doc/draft-ietf-lpwan-coap-static-context-hc/ballot/#magnus-westerlund
). 

Let me try to re-iterate on why I think my discuss is relevant and you should do
something credible to address it. 

So my discuss are really only focused on the case where SCHC is used on top of a
security layer that pushes the SCHC implementation into the COAP stacks at the
end-points, rather than potentially lower layers on top of the L2
infrastructure. 

To me it appears that this change results in several architectural
considerations that didn't existed before for the entity that are going to
determine the SCHC capability in the peer as well as the context establishment. 
What I am asking for is really only an description of the changed architectural
context and the requirements on a solution for the SCHC context establishment
mechanism. 

- Discover the peers capability to perform SCHC for COAP or can one
opportunisticly try? 
- Taking into account that an COAP application can potentially talk to a number
of peers, each having different capabilities. 
- Are there need for a redirection/invocation mechanism
- The actual context exchange mechanism. 

Can we please write a paragraph or two in the suitable section in this document
rather a single sentence pointing to an appendix. That appending containing a
single bullet that are supposed to be added:

   This section extends the RFC8724 Annex D list.

   o  How to establish the End-to-End context initialization using SCHC
      for CoAP header only.

Annex D of RFC 8724 list is preface by:
"This section lists the information that needs to be provided in the LPWAN
technology-specific documents."

That is not really information to be provided, there are procedures that are
needed. 

Cheers

Magnus Westerlund 

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