Subject: [rtcweb] DataChannel Questions

From: Roman Shpount <[email-masked]>
Date: Mon, 22 Jul 2013 14:15:16 -0400

I am sorry if I missed this somewhere in the draft, but I got two
DataChannel related questions:

First question: is it possible to bundle DataChannel with DTLS-SRTP? I do
not see how this can be implemented since DTLS in DataChannel can negotiate
any encryption protocol and I do not see a simple way to de-mux this on the
wire. Just wanted to confirm that bundling is not something that is planned
to be supported.

Second question: is there a way to time synchronize DataChannel messages
and real time media? For instance I want to use DataChannel for a subtitle
track, is there a way to synchronize messages with video track?
_____________
Roman Shpount

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From: Eric Rescorla <[email-masked]>
Date: Mon, 22 Jul 2013 11:20:14 -0700

On Mon, Jul 22, 2013 at 11:15 AM, Roman Shpount <[email-masked]> wrote:

> wire.

I don't understand that "negotiate any encryption protocol" means. The SCTP
in the
DataChannel is encrypted under DTLS. The only potential problem here could
be
demuxing the SCTP from non-SCTP traffic once you have demuxed DTLS versus
SRTP, but we don't support anything that's non-SCTP here yet.

> Just wanted to confirm that bundling is not something that is planned to
> be supported.
>

As far as I know, it's fine.

> track, is there a way to synchronize messages with video track?

You would presumably need to add the timing data into the DC messages
themselves, since SCTP does not provide any real-time function.

-Ekr

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From: Roman Shpount <[email-masked]>
Date: Mon, 22 Jul 2013 14:32:59 -0400

Thank you for you response. It is all clear now.
_____________
Roman Shpount