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

Carles Gomez Montenegro <> Thu, 22 April 2021 10:13 UTC

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Date: Thu, 22 Apr 2021 12:21:20 +0200
From: Carles Gomez Montenegro <>
To: Martin Duke <>
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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.


Carles (on behalf of all the authors)

> Martin Duke has entered the following ballot position for
> draft-ietf-6lo-blemesh-09: Discuss
> When responding, please keep the subject line intact and reply to all
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> introductory paragraph, however.)
> Please refer to
> for more information about IESG DISCUSS and COMMENT positions.
> The document, along with other ballot positions, can be found here:
> ----------------------------------------------------------------------
> ----------------------------------------------------------------------
> 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.