Re: [babel] I-D Action: draft-ietf-babel-v4viav6-00.txt

Juliusz Chroboczek <> Thu, 08 April 2021 12:22 UTC

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Date: Thu, 08 Apr 2021 14:22:43 +0200
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From: Juliusz Chroboczek <>
To: Donald Eastlake <>
Cc: Babel at IETF <>, babel-chairs <>
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Subject: Re: [babel] I-D Action: draft-ietf-babel-v4viav6-00.txt
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> specifically slides 5 through the end.

> I think slides 10 and 11 cover the practical choices. Any feedback or
> opinions welcome.

To restate the opinion I presented during my talk: the dependency of PMTUd
on ICMP is the fundamental problem here, since it breaks the end-to-end
nature of TCP.  The Babel WG is however not the right forum to redesign
PMTUd.  無.

The draft should merely say that every IPv4 router MUST be able to send
ICMPv4 packets.  How this is realised is an implementation detail -- the
v4 address could be assigned to the outgoing interface, to the router as
a whole, or a fallback address hard-wired in the ICMPv4 module.  The draft
should also state that the router need not be able to receive packets
destined to that address, and that the address need not be locally or
globally unique.  It should discuss debuggability issues, perhaps in an
informative appendix.

> There is one other question in my mind. Does this draft really need to
> be Experimental? I would be inclined to target it to Proposed Standard.

I'm a little uneasy on this subject.  My personal feeling is that we
haven't done our homework on this extension (admittedly my fault), and
that we don't have enough implementation and deployment experience to
propose it as a standard right now.

I'd be delighted if people could disagree.

-- Juliusz