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

Magnus Westerlund <> Thu, 21 March 2013 10:15 UTC

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Date: Thu, 21 Mar 2013 11:15:17 +0100
From: Magnus Westerlund <>
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Subject: Re: [MMUSIC] Review of draft-ietf-mmusic-sctp-sdp-03
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On 2013-03-20 17:55, Paul Kyzivat wrote:
> Magnus,
> Some comments on your review, from a CLUE perspective:
> On 3/20/13 11:11 PM, Magnus Westerlund wrote:
>> 6. Section 4.1:
>> This section discuss the usage of the "data channels" within the SCTP
>> association. My personal position is that for the moment this appears to
>> be unnecessary. The most important part is the SCTP association
>> establishment. Then one can discuss the general application using the
>> SCTP association as whole. Examples of such are WebRTC data channel.
>> If anyone want stream level information in SDP then I propose that this
>> is handled as a extension to this signaling, not an from the start
>> included functionality as we don't appear to have clear requirement for
>> that.
> Who is "we"?


> In CLUE we expect to use this mechanism for a CLUE data channel.
> And we intend to do so in pure sip-sip cases as well as webrtc-sip and
> webrtc-webrtc cases.

> 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.

>> 7. Section 4.2:
>> What are the requirements behind being able to establish multiple SCTP
>> association over the same DTLS connection? I am very unclear why this
>> would be required, and if not really needed I would suggest keeping
>> things simple.
> I agree there has been no compelling need advanced for multiple SCTP
> associations over the same DTLS connection. But the fact is that SCTP
> has its own notion of port, and that needs to be dealt with one way or
> another. At a minimum this document should specify what SCTP port is to
> be used when conforming to this specification.

Agreed, there need to be clarity on the port usage.

>> 8. Section 4.3: I guess this can for the moment be removed as it appears
>> to be taken care in other places, such as the RTCWEB WG data channel
>> protocol proposal.
> See above. That doesn't meet CLUE needs.

Disagree, I don't think CLUE need SCTP stream specific indication or
negoitation. It will be sufficient to indicate that this is CLUE using SCTP.


Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVM
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