Re: [MMUSIC] Bundling data channel and RTP? - Text proposal

Christer Holmberg <> Wed, 27 May 2015 17:17 UTC

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From: Christer Holmberg <>
To: Roman Shpount <>, "Makaraju, Maridi Raju (Raju)" <>
Thread-Topic: [MMUSIC] Bundling data channel and RTP? - Text proposal
Date: Wed, 27 May 2015 17:17:25 +0000
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Subject: Re: [MMUSIC] Bundling data channel and RTP? - Text proposal
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I guess we could add some text to the DTLS Considerations section.



Sent from my Windows Phone
From: Roman Shpount<>
Sent: ‎27/‎05/‎2015 23:31
To: Makaraju, Maridi Raju (Raju)<>
Cc: Christer Holmberg<>; Christian Groves<>;<>;<>
Subject: Re: [MMUSIC] Bundling data channel and RTP? - Text proposal

On Wed, May 27, 2015 at 7:37 AM, Makaraju, Maridi Raju (Raju) <<>> wrote:
> >One interesting question that Albrecht brought up in a separate email
> discussion is what happens if you first establish a >DTLS association
> for datachannel and then at a later stage you add SRTP media? I take it
> that you'd have to re-establish >the DTLS connection and perform a
> handshake using the "use_srtp" extension. That makes transitioning
> messy.
> There is a related (not BUNDLE specific) discussion on when one is
> allowed to re-establish a DTLS connection, and the idea (I don't have
> the exact details in front of me) is that it can happen only when an IP
> address or port changes. That obviously does not have to occur if you
> add SRTP.
Will there be an issue if "use_srtp" extension is always included even when
SRTP media is not present at that time? I don't see any issue.
This is how Chrome works today; it always includes the extension.

I agree, DTLS session should always be setup with "use_srtp" extension. There is little or no additional overhead, but this removes the latency required for a new DTLS session when and if SRTP is added. Since there is no new DTLS session there is no need for a new underlying transport and additional IPs. Nice and clean.

This should probably be stated somewhere in the document.
Roman Shpount