Re: [MMUSIC] Review of draft-ietf-mmusic-sctp-sdp-03

Magnus Westerlund <> Fri, 22 March 2013 10:18 UTC

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Date: Fri, 22 Mar 2013 11:18:09 +0100
From: Magnus Westerlund <>
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Subject: Re: [MMUSIC] Review of draft-ietf-mmusic-sctp-sdp-03
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On 2013-03-21 21:01, Paul Kyzivat wrote:
> On 3/21/13 6:15 PM, Magnus Westerlund wrote:
>> On 2013-03-20 17:55, Paul Kyzivat wrote:
>>> While webrtc-webrtc may have an independent mechanism to work out the
>>> channel usage, that is certainly not so for sip-sip sessions.
>>> So I think "we" (CLUE) have a requirement to negotiate channel usage in
>>> SDP.
>> Do you? Or it is sufficient to say
>> m=application 12234 UDP/DTLS/SCTP CLUE
>> Indicating that this SCTP association is using CLUEs defined way, not
>> WebRTC. I want to separate the usage of individual SCTP streams and the
>> general usage of the SCTP association.
> Then what do we do for an WEBRTC client doing CLUE, talking to a native
> sip CLUE endpoint?
> I guess clue could live with a mechanism that reserves the complete SCTP
> association, with all of its streams, as globally managed in a
> clue-specific way, as long as we can sort out the interop with webrtc.

What I understand you can't really in the general case sort out the
WebRTC interoperability. WebRTC is after all a JavaScript specific usage
of a generic bi-directional multi-channel data transmission. Where the
generic bi-directional paradigm is realized using RTCWEB defined data
protocol. Clue could reuse that basic scheme but it would not make it
clear about will be on specific channels, that can be explicit or
implicit and depends on the WebRTC application.

It might be that certain usages becomes standardized and that we can
agree on labeling them and interconnect them with other systems. Doest
that need to happen in SDP. Don't think so. What I think will be
happening is that when you like to connect to a CLUE system using a
WebRTC supporting browser then you deploy a CLUE speaking JS, that will
use the data channel in a CLUE agreed way requiring minimal translation.
In fact the only adaptation is likely that the PeerConnection peer must
be capable of accepting peerConnections and interconnect them with a
CLUE system. In such system I don't see the WebRTC endpoint indicating
that it is CLUE interoperable, it is the CLUE JS APP plus the WebRTC to
CLUE gateway that ensures that this works. No changes to the WebRTC browser.


Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVM
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