Subject: [lp-wan] Fwd: New Version Notification for draft-ietf-lpwan-coap-static-context-hc-08.txt

From: Laurent Toutain <[email-masked]>
Date: Wed, 29 May 2019 19:55:25 +0200

Hi,

We have issued a new version of the SCHC coap compression to remove an
artifact due to a bad github manipulation.

Laurent

---------- Forwarded message ---------
From: <[email-masked]>
Date: Wed, May 29, 2019 at 7:51 PM
Subject: New Version Notification for
draft-ietf-lpwan-coap-static-context-hc-08.txt
To: Laurent Toutain <[email-masked]>, Ana Minaburo <
[email-masked]>, Ricardo Andreasen <[email-masked]>, Laurent Toutain <
[email-masked]>, <[email-masked]>

A new version of I-D, draft-ietf-lpwan-coap-static-context-hc-08.txt
has been successfully submitted by Laurent Toutain and posted to the
IETF repository.

Name:           draft-ietf-lpwan-coap-static-context-hc
Revision:       08
Title:          LPWAN Static Context Header Compression (SCHC) for CoAP
Document date:  2019-05-29
Group:          lpwan
Pages:          29
URL:
https://www.ietf.org/internet-drafts/draft-ietf-lpwan-coap-static-context-hc-08.txt
Status:
https://datatracker.ietf.org/doc/draft-ietf-lpwan-coap-static-context-hc/
Htmlized:
https://tools.ietf.org/html/draft-ietf-lpwan-coap-static-context-hc-08
Htmlized:
https://datatracker.ietf.org/doc/html/draft-ietf-lpwan-coap-static-context-hc
Diff:
https://www.ietf.org/rfcdiff?url2=draft-ietf-lpwan-coap-static-context-hc-08

Abstract:
   This draft defines the way SCHC header compression can be applied to
   CoAP headers.  The CoAP header structure differs from IPv6 and UDP
   protocols since CoAP
   uses a flexible header with a variable number of options themselves
   of variable length.  The CoAP protocol is asymmetric in its message
   format, the format of the header packet in the request messages is
   different from that in the response messages.  Most of the
   compression mechanisms have been introduced in
   [I-D.ietf-lpwan-ipv6-static-context-hc], this document explains how
   to use the SCHC compression for CoAP.

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

The IETF Secretariat

---

From: Thomas Fossati <[email-masked]>
Date: Thu, 30 May 2019 12:52:33 +0100

Hi Laurent,

On Wed, May 29, 2019 at 6:56 PM Laurent Toutain
<[email-masked]> wrote:
> We have issued a new version of the SCHC coap compression
> to remove an artifact due to a bad github manipulation.

I have taken a look at the draft but since I cannot claim compression
expertise I will only provide a couple of high level comments:
- Sec 3: "a proxy placed before the compressor may change some field
value".  You should qualify the "proxy" as a "CoAP proxy, explicitly
selected by the client" to avoid any ambiguity -- we certainly don't
want to recommend middle-box interference :-)
- Sec 4.1: "This field is bidirectional and MUST be elided during the
SCHC compression". This is a dangerous statement as it leads us
straight into CoAP ossification territory.  If you want SCHC to work
with CoAP v1 only what you really want to say here is "SHCH
compression MUST NOT be applied to CoAP packets with version different
from v1".  Granted that, a SCHC box deployed today could sit in the
field happily ever after.  If not, when a new CoAP version is rolled
out, endpoints wouldn’t be able to use this new version on any path
crossing an SCHC box.

Cheers!