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

From: Martin Duke via Datatracker <[email-masked]>
Date: Tue, 23 Feb 2021 15:55:42 -0800

Martin Duke has entered the following ballot position for
draft-ietf-6lo-blemesh-09: Discuss

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DISCUSS:
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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.