Re: [rtcweb] Unsolicited DTLS Handshake

Iñaki Baz Castillo <> Wed, 03 December 2014 14:59 UTC

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From: =?UTF-8?Q?I=C3=B1aki_Baz_Castillo?= <>
Date: Wed, 3 Dec 2014 15:58:53 +0100
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To: Christer Holmberg <>
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Subject: Re: [rtcweb] Unsolicited DTLS Handshake
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2014-12-03 13:09 GMT+01:00 Christer Holmberg <>om>:

> First, we need to agree on whether support of rekeying and renegotiation is mandatory, optional or not supported in general.

WebRTC uses DTLS. DTLS allows that, so it must be supported. This is,
any WebRTC device/endpoint/thing should be able to perform a DTLS
renegotiation (regardless who sent the first ClientHello), and that
could involve SRTP re-keyring. This is 100% transparent so no need at
all for SDP O/A stuff.

> Second, we need to agree on how/if an updated offer affects an existing DTLS connection.
> - If the transport parameters have changed, a new DTLS connection is obviously needed. But, then, how are the roles determined? Using the SDP setup attribute, as in the initial offer? OR, do we use the roles determined in the initial offer?

Each SDP O/A party is supposed to mean an independent round-trip, so
the same mechanism used for the original SDP O/A should be used. Said

What would happen in a SDP O/A renegotiation if "transport parameters"
do not change but the a=setup attribute does change? Well, the world
end. We are trying to signal everything in SDP but at the same time we
use protocols that are self-sufficient, so yes, we get unnecessary

Iñaki Baz Castillo