Re: [MMUSIC] Proto identifier: To UDP or not to UDP (Re: Review of draft-ietf-mmusic-sctp-sdp-03)

Magnus Westerlund <> Fri, 22 March 2013 10:21 UTC

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Date: Fri, 22 Mar 2013 11:21:22 +0100
From: Magnus Westerlund <>
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Subject: Re: [MMUSIC] Proto identifier: To UDP or not to UDP (Re: Review of draft-ietf-mmusic-sctp-sdp-03)
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On 2013-03-21 14:22, Harald Alvestrand wrote:
> One high level comment:
> This series of comments points out that the purpose of the thing called
> "proto identifier" in SDP is not really well documented.
> As far as I can tell, the requirement is that it uniquely identifies the
> parser one needs to use for the stuff under this m= line, and that is
> the sum total of the requirements on it - as we painfully learned with
> RTP/AVP, RTP/AVPF, SRTP/AVP and SRTP/AVPF, making detailed information
> about the parameters available via the "proto identifier" is not really
> a Good Idea.
> I suggest we go for DTLS/SCTP, as specified in the document currently,
> and document that the lower layer used has to be identified from the
> elements inside the m= line block; if there is ICE, ICE can negotiate
> it; if there is only a port number, it's UDP; if there are more
> extensions to specify that the lower layer is LTE over pterodactyls, the
> identifier doesn't change.

I am fine with this and it is likely the most pragmatic choice. However,
the current draft is not clear on the lower layer at all. If it adds
this and makes it clear on the handling I don't see an issue. Especially
as what ICE provides may not be UDP at all.


Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVM
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