Re: [MMUSIC] Bundling data channel and RTP? - Text proposal

Paul Kyzivat <pkyzivat@alum.mit.edu> Mon, 25 May 2015 16:22 UTC

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Date: Mon, 25 May 2015 12:22:12 -0400
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Subject: Re: [MMUSIC] Bundling data channel and RTP? - Text proposal
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On 5/25/15 3:14 AM, Christer Holmberg wrote:
> Hi,
>
> Below is a suggestion for a "DTLS considerations" section. Let me know if you think there are more rules/restrictions that we should document.

My reply to your other message implies that it is probably important to 
say more than this.

Also, I *think* it is possible to mix RTP over UDP with RTP over DTLS in 
the same bundle. (Though I can't think of any utility to doing so.) I 
don't think what you say below is inconsistent with that, but it might 
be good to think through the implications.

	Thanks,
	Paul

> --------------------
>
> X.  DTLS Considerations
>
> 	One or more media streams within a BUNDLE group can use
> 	the Datagram Transport Layer Security (DTLS) protocol [RFC6347]
> 	in order to encrypt the data, or to negotiate encryption keys
> 	if another encryption mechanism is used to encrypt media.
>
> 	When DTLS is used for more than one media stream within a BUNDLE
> 	group, the following rules apply:
>
> 	o  A single DTLS association [RFC6347] MUST be used for all media
> 	using DTLS; and
> 	
>     	o  Each media protocol using DTLS MUST use the same mechanism for
> 	determining which endpoint (the offerer or answerer) becomes DTLS client and DTLS server.
>
> --------------------
>
> Regards,
>
> Christer
>
>
>
> -----Original Message-----
> From: mmusic [mailto:mmusic-bounces@ietf.org] On Behalf Of Christer Holmberg
> Sent: 25 May 2015 04:59
> To: Christian Groves; mmusic@ietf.org
> Subject: Re: [MMUSIC] Bundling data channel and RTP?
>
> Hi,
>
> I wonder whether we should have a "DTLS considerations" section in BUNDLE, and specify that all bundled media MUST use the same DTLS connection for key management, encryption etc.
>
> Would it even be possible to establish multiple DTLS connections on a single 5-tuple?
>
> Regards,
>
> Christer
>
> -----Original Message-----
> From: mmusic [mailto:mmusic-bounces@ietf.org] On Behalf Of Christian Groves
> Sent: 22 May 2015 10:20
> To: mmusic@ietf.org
> Subject: Re: [MMUSIC] Bundling data channel and RTP?
>
> 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
>>
>> ----------------------------------------------------------------------
>> Services, Media and Network features, Ericsson Research EAB/TXM
>> ----------------------------------------------------------------------
>> Ericsson AB                 | Phone  +46 10 7148287
>> Färögatan 6                 | Mobile +46 73 0949079
>> SE-164 80 Stockholm, Sweden | mailto: magnus.westerlund@ericsson.com
>> ----------------------------------------------------------------------
>>
>>
>
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