Re: [6lo] Martin Duke's Discuss on draft-ietf-6lo-blemesh-09: (with DISCUSS)

Carles Gomez Montenegro <carlesgo@entel.upc.edu> Thu, 22 April 2021 10:13 UTC

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Date: Thu, 22 Apr 2021 12:21:20 +0200
From: "Carles Gomez Montenegro" <carlesgo@entel.upc.edu>
To: "Martin Duke" <martin.h.duke@gmail.com>
Cc: "The IESG" <iesg@ietf.org>, rahul.ietf@gmail.com, 6lo-chairs@ietf.org, draft-ietf-6lo-blemesh@ietf.org, 6lo@ietf.org
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Archived-At: <https://mailarchive.ietf.org/arch/msg/6lo/YQquNdboUJDqQ2ZyI7xGLGnSUjM>
Subject: Re: [6lo] Martin Duke's Discuss on draft-ietf-6lo-blemesh-09: (with DISCUSS)
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Hi Martin,

Thank you very much for your feedback, and apologies for the late response.

We just published an updated version of the draft (revision -10).

Regarding your Discuss point, after discussion among the authors and with
the WG, we aim to address the issue by stating now that:

  “As per the present specification, the MTU size for IPv6 mesh over BLE
   links is 1280 octets.”

(Initially we thought that it might be a good idea to keep the flexibility
offered by the IPSP in this regard, but we finally realized that it was
not such a good idea.)

Should you have further comments, please let us know.

Thanks,

Carles (on behalf of all the authors)



> Martin Duke has entered the following ballot position for
> draft-ietf-6lo-blemesh-09: Discuss
>
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> for more information about IESG DISCUSS and COMMENT positions.
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> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-ietf-6lo-blemesh/
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>
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
>
> I found this paragraph in Section 3.1 to be hand-wavy:
>
> "Note that this specification allows using different MTUs in different
>    links.  If an implementation requires use of the same MTU on every
>    one of its links, and a new node with a smaller MTU is added to the
>    network, a renegotiation of one or more links can occur.  In the
>    worst case, the renegotiations could cascade network-wide.  In that
>    case, implementers need to assess the impact of such phenomenon."
>
> What are the consequences of link "renegotiation"? If every MTU downgrade
> results in a storm of messages, that's a bad property. Is the use case
> where
> the MTU must be the same on all links an important one? If not, simply
> requiring hosts to handle this case seems way cleaner.