Re: [MMUSIC] draft-ietf-mmusic-sctp-sdp-07 SCTP SDP syntax question

Christer Holmberg <christer.holmberg@ericsson.com> Thu, 02 October 2014 18:32 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Paul Kyzivat <pkyzivat@alum.mit.edu>, "mmusic@ietf.org" <mmusic@ietf.org>
Thread-Topic: [MMUSIC] draft-ietf-mmusic-sctp-sdp-07 SCTP SDP syntax question
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Date: Thu, 2 Oct 2014 18:31:56 +0000
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Archived-At: http://mailarchive.ietf.org/arch/msg/mmusic/TDyth-dRYvhWCed4o5z4klyoWf8
Subject: Re: [MMUSIC] draft-ietf-mmusic-sctp-sdp-07 SCTP SDP syntax question
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Hi,

>> Keep in mind that the purpose of draft-ejzak-mmusic-data-channel-sdpneg is NOT to negotiate 
>> the usage of the SCTP association.
>>
>> It is assumed that the usage of the SCTP association is data channel, and the draft defines a 
>> mechanism to negotiate data channels on that SCTP association.
>
> The purpose is to negotiate the use of channels, which is almost the same as negotiating the use of > individual SCTP streams within an SCTP association.

Correct. But, it is not used to negotiate the SCTP association usage, which I think is what Christian has been talking about. It assumes that the SCTP association is used for data channels.

Regards,

Christer



> -----Original Message-----
> From: mmusic [mailto:mmusic-bounces@ietf.org] On Behalf Of Paul 
> Kyzivat
> Sent: 2. lokakuuta 2014 4:37
> To: mmusic@ietf.org
> Subject: Re: [MMUSIC] draft-ietf-mmusic-sctp-sdp-07 SCTP SDP syntax 
> question
>
> On 10/1/14 7:57 PM, Christian Groves wrote:
>> What is the status of the draft-ejzak-mmusic-data-channel-sdpneg-00?
>
> I don't know the status. The thought Keith Drage had indicated that he was picking up responsibility for it.
>
> 	Thanks,
> 	Paul
>
>> It has expired and is based on the old SDP SCTP syntax. Particularly 
>> the example in cl.4:
>>
>>      m=application 54111 DTLS/SCTP 5000 5001 5002
>>      c=IN IP4 79.97.215.79
>>      a=sctpmap:5000 webrtc-datachannel
>>      a=sctpmap:5001 bfcp
>>      a=sctpmap:5002 t38
>>
>> Wouldn't apply if we're saying to use multiple m-lines.
>>
>> I guess cl.5.1.1.3 would use the same Websocket subprotocol name 
>> registry as data channel does?
>>
>> Regards, Christian
>>
>> On 2/10/2014 12:14 AM, Paul Kyzivat wrote:
>>> On 10/1/14 3:44 AM, Christian Groves wrote:
>>>
>>>>> <Sal>
>>>>> there have been several discussion about the ability to have more 
>>>>> than one usage of the SCTP association, and has been agreed not to 
>>>>> allow it.
>>>>> So each 'm' line describes a single SCTP association;  each 
>>>>> association has only one single specify usage.
>>>>> </Sal>
>>>>
>>>> [CNG] So how would I specify in SDP a scenario where BFCP uses a 
>>>> DTLS/SCTP association and MSRP uses a DTLS/SCTP association where 
>>>> they both use the same DTLS connection? Are these to be separate m-lines?
>>>
>>> To have two different SCTP associations over the same DTLS 
>>> connection, they would have to be distinguished by sctp-port. To 
>>> achieve that you could write two m-lines. They would share the same 
>>> ip address and port, and would have different "a=sctp-port" lines.
>>> Then they would have to be bundled.
>>>
>>> Doing that would require extending the definition of bundle to cover 
>>> that case. (There is no *technical* problem in doing this.)
>>>
>>> OTOH, in principle they don't need their own SCTP association. AFAIK 
>>> they each only use one sctp stream-pair (channel). If they could 
>>> agree on how to choose channels then they could share an SCTP association.
>>> That is where draft-ejzak... comes in.
>>>
>>>      Thanks,
>>>      Paul
>>>
>>> _______________________________________________
>>> mmusic mailing list
>>> mmusic@ietf.org
>>> https://www.ietf.org/mailman/listinfo/mmusic
>>>
>>
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