Re: [MMUSIC] SCTP question: Where does it multiplex?

[Harald Alvestrand <[e-mail]>]

On 12/11/2012 04:43 PM, Paul Kyzivat wrote:
> More inline.
>
> On 12/11/12 4:08 AM, Salvatore Loreto wrote:
>> Hi Paul,
>>
>> see in line!
>>
>> On 12/3/12 10:00 PM, Paul Kyzivat wrote:
>>> Commenting on a different point
>>>
>>> On 12/1/12 9:53 AM, Harald Alvestrand wrote:
>>>
>>>> The interesting difference is that the multiplexing between DTLS/SCTP
>>>> traffic and BUNDLE multiplexing is that DTLS/SCTP traffic is not 
>>>> carried
>>>> in SSRCs, which means:
>>>>
>>>> - There can be only one DTLS/SCTP stream in a bundle (which may have
>>>> multiple associations, as you state below); you can't have multiple
>>>> lines with proto DTLS/SCTP in a bundle.
>>>
>>> I am not an SCTP expert. But IIUC, SCTP was designed to run directly
>>> over IP. It has its own notion of port used to demux multiple SCTP
>>> associations over the same IP address.
>>>
>>> I presume that that same mechanism is still there when SCTP is run
>>> over DTLS over UDP.
>>>
>>> So, the traffic coming over DTLS must first be demuxed into RTP
>>> traffic and SCTP traffic.
>> based on the current stack the SCTP traffic is the only traffic that
>> runs directly over the DTLS stack.
>
> Yes, that is what I thought. But Harald has been asking about 
> multiplexing this with RTP traffic. (Actually I think it would be 
> DTLS/SRTP traffic that it would be multiplexed with.)
Yes, it's SRTP traffic that the DTLS/SCTP traffic will be multiplexed 
with (the DTLS part of DTLS/SRTP is just a key negotiation mechanism, 
unlike the DTLS part of DTLS/SCTP, which is an actual encapsulation).