Re: [MMUSIC] Bundling data channel and RTP?

Christian Groves <Christian.Groves@nteczone.com> Fri, 22 May 2015 07:20 UTC

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Date: Fri, 22 May 2015 17:20:04 +1000
From: Christian Groves <Christian.Groves@nteczone.com>
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Subject: Re: [MMUSIC] Bundling data channel and RTP?
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Hello Magnus and Martin,

Thanks for confirming that.

It would be good to cover bundling the SRTP and DTLS/SCTP m-lines the BUNDLE and JSEP drafts.

Regards, Christian



On 20 May 2015 at 17:21, Christian Groves<Christian.Groves@nteczone.com>  wrote:

> Can anyone confirm the intention that a single DTLS connection is used for
> SRTP key exchange and also SCTP packets?

Yes, the record layer carries SCTP and exporters from the same session
are used to key SRTP.



On 21/05/2015 7:34 PM, Magnus Westerlund wrote:
> Christian Groves skrev den 2015-05-21 02:21:
>> Can anyone confirm the intention that a single DTLS connection is used
>> for SRTP key exchange and also SCTP packets?
>>
>> draft-ietf-rtcweb-transports-08 indicates:
>>
>> /WebRTC implementations MUST support multiplexing of DTLS and RTP over//
>> //   the same port pair, as described in the DTLS_SRTP specification//
>> //   [RFC5764], section 5.1.2.  All application layer protocol 
>> payloads//
>> //   over this DTLS connection are SCTP packets./
>>
>> To me this implies a single DTLS connection. However in RFC5764 clause
>> 4.1 it says:
>> /Once the "use_srtp" extension is negotiated, the RTP or RTCP//
>> //   application data is protected solely using SRTP. Application 
>> data is//
>> //   never sent in DTLS record-layer "application_data" packets.  
>> Rather,//
>> //   complete RTP or RTCP packets are passed to the DTLS stack, which//
>> //   passes them to the SRTP stack, which protects them appropriately.//
>> /
>> In the second sentence "application data" is not qualified with "RTP or
>> RTCP" so it could be taken that its not possible to use the DTLS
>> connection for anything else. However I take it that as the rest of the
>> paragraph talks about RTP or RTCP that these were meant when application
>> data is mentioned?
>>
>> Can only one add some clarity?
>>
>
> Yes, that is clearly the intention as I understand it in WebRTC.
>
> Cheers
>
> Magnus Westerlund
>
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