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Re: [babel] Mirja Kühlewind's Discuss on draft-ietf-babel-dtls-07: (with DISCUSS and COMMENT)

Juliusz Chroboczek <jch@irif.fr> Thu, 08 August 2019 11:17 UTC

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Date: Thu, 08 Aug 2019 13:17:08 +0200
Message-ID: <87a7cjq53f.wl-jch@irif.fr>
From: Juliusz Chroboczek <jch@irif.fr>
To: Mirja Kuehlewind <ietf@kuehlewind.net>
Cc: David Schinazi <dschinazi.ietf@gmail.com>, The IESG <iesg@ietf.org>, draft-ietf-babel-dtls@ietf.org, Donald Eastlake <d3e3e3@gmail.com>, babel-chairs <babel-chairs@ietf.org>, Babel at IETF <babel@ietf.org>
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Subject: Re: [babel] Mirja Kühlewind's Discuss on draft-ietf-babel-dtls-07: (with DISCUSS and COMMENT)
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>> Using an ephemeral port that is discovered at runtime would add a failure mode
>> to the protocol and make it less robust.

> Can you please explain why that would make it less robust? I would
> actually think that is would make it more robust. In any case you need
> to somehow discovery the neighbour. Usually the babel HELLO would be
> used for that. When you add an new TLV to that HELLO that indicates
> a port that should be used for DTLS, this also gives you and additional
> indication that the peer sending the hello actually supports DTLS which
> I believe would make it more robust.

That's an intruiguing idea.

> Further with respect to security and topics probably recently discussed, not having a default port would make it harder for an attacker to flood a route with DTLS handshakes on that port.

Could you please explain what happens if an attacker sends out 65535
spoofed multicast Hellos indicating 65535 distinct ports?

-- Juliusz

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