Re: [MMUSIC] Bundling data channel and RTP?

[Paul Kyzivat <[e-mail]>]

On 5/25/15 8:50 PM, Christer Holmberg wrote:
> 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.
>>
>> Yes, that makes sense.
>>
>>> Would it even be possible to establish multiple DTLS connections on a single 5-tuple?
>>
>> I don't think so.
>>
>> Note that RTP is "special" in this regard, in that it uses DTLS for the keying, but
>> it doesn't use DTLS payload packets.
>>
>> If there were more than one m-line that used DTLS payload packets then they
>> would also have to specify how to multiplex among them. AFAIK there is currently
>> no way to do that, so there can only be one m-line that uses DTLS payload packets.
>
> This is covered in section 9.

OK. Sorry.

	Paul

> Section 9.2 contains the following statement:
>
> 	"[RFC5764] does not describe how to identify different protocols
>     	transported on DTLS, only how to identify the DTLS protocol itself.
>     	If multiple protocols are transported on DTLS, there MUST exist a
>     	specification describing a mechanism for identifying each individual
>     	protocol. In addition, if a received DTLS packet can be associated
>     	with more than one "m=" line, there MUST exist a specification which
>     	describes a mechanism for associating the received DTLS packet with
>     	the correct "m=" line."
>
> Regards,
>
> Christer
>
>
>
>> -----Original Message-----
>> From: mmusic [mailto:[e-mail]] On Behalf Of Christian
>> Groves
>> Sent: 22 May 2015 10:20
>> To: [e-mail]
>> 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<[e-mail]>  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  [phone]
>>> Färögatan 6                 | Mobile [phone]
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>>> -
>>>
>>>
>>
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