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

Roman Shpount <roman@telurix.com> Wed, 27 May 2015 15:31 UTC

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Date: Wed, 27 May 2015 11:31:22 -0400
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From: Roman Shpount <roman@telurix.com>
To: "Makaraju, Maridi Raju (Raju)" <Raju.Makaraju@alcatel-lucent.com>
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Cc: "mmusic@ietf.org" <mmusic@ietf.org>, "pkyzivat@alum.mit.edu" <pkyzivat@alum.mit.edu>, Christer Holmberg <christer.holmberg@ericsson.com>
Subject: Re: [MMUSIC] Bundling data channel and RTP? - Text proposal
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On Wed, May 27, 2015 at 7:37 AM, Makaraju, Maridi Raju (Raju) <
Raju.Makaraju@alcatel-lucent.com> 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.
> [Raju]
> 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