Re: [AVTCORE] [TLS] WG last call of draft-ietf-avtcore-rfc5764-mux-fixes-05

Martin Thomson <> Wed, 02 March 2016 22:48 UTC

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Date: Thu, 03 Mar 2016 09:48:00 +1100
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From: Martin Thomson <>
To: Marc Petit-Huguenin <>
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Cc: Magnus Westerlund <>, Joseph Salowey <>, "" <>, "" <>, Dave Garrett <>
Subject: Re: [AVTCORE] [TLS] WG last call of draft-ietf-avtcore-rfc5764-mux-fixes-05
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On 3 March 2016 at 09:20, Marc Petit-Huguenin <> wrote:
> draft-ietf-avtcore-rfc5764-mux-fixes does not reserve large portions of the ContentType codepoints, RFC 5764 did.  The damage is already done as RFC 5764 is deployed as a component of RTCWeb.

I think that we can resolve this by saying this instead:

RFC 5764 describes a narrow use of DTLS that works as long as the
specific DTLS version used abides by the restrictions on the first
byte (the ones that mux-fixes wants to put in the TLS registry).  Any
extension or revision to DTLS that no causes DTLS to no longer meet
these constraints prevents that extension or version from being used
in the fashion RFC 5764 describes.

That means that DTLS 1.2 is safe.  Thus far.  DTLS 1.3 is also safe so
far, though we're a lot further from done there[3].

I'm sorry that I didn't see this option before; I figured that with
content type encryption in TLS 1.3, we wouldn't need those code
points.  However, Joe is right to protest the incursion onto sovereign

[3]  I actually hope that we can change DTLS 1.3 so that it won't mux
properly.  That will have a size benefit that should outweigh the cost
of having to rev 5764 for 1.3.