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

Christian Groves <Christian.Groves@nteczone.com> Thu, 28 May 2015 00:06 UTC

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Date: Thu, 28 May 2015 10:06:18 +1000
From: Christian Groves <Christian.Groves@nteczone.com>
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To: Christer Holmberg <christer.holmberg@ericsson.com>, Roman Shpount <roman@telurix.com>, "Makaraju, Maridi Raju (Raju)" <Raju.Makaraju@alcatel-lucent.com>
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Subject: Re: [MMUSIC] Bundling data channel and RTP? - Text proposal
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To be clear this means that the SRTP and SRTCP ( (because of the 
possibility of RTP/RTCP muxing) key negotiation occurs even before 
RTP/STRP media is added to the BUNDLE, and the keying material for both 
are maintained for the life of the BUNDLE? If the keys are unused they 
wouldn't expire because max lifetime is based on the number of protected 
packets.

Christian

On 28/05/2015 3:17 AM, Christer Holmberg wrote:
> Hi,
>
> I guess we could add some text to the DTLS Considerations section.
>
> Regards,
>
> Christer
>
> Sent from my Windows Phone
> ------------------------------------------------------------------------
> From: Roman Shpount <mailto:roman@telurix.com>
> Sent: ‎27/‎05/‎2015 23:31
> To: Makaraju, Maridi Raju (Raju) <mailto:Raju.Makaraju@alcatel-lucent.com>
> Cc: Christer Holmberg <mailto:christer.holmberg@ericsson.com>; 
> Christian Groves <mailto:Christian.Groves@nteczone.com>; 
> mmusic@ietf.org <mailto:mmusic@ietf.org>; pkyzivat@alum.mit.edu 
> <mailto:pkyzivat@alum.mit.edu>
> Subject: Re: [MMUSIC] Bundling data channel and RTP? - Text proposal
>
>
>
> On Wed, May 27, 2015 at 7:37 AM, Makaraju, Maridi Raju (Raju) 
> <Raju.Makaraju@alcatel-lucent.com 
> <mailto: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
>