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

<> Tue, 11 December 2012 10:34 UTC

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Thread-Topic: [MMUSIC] SCTP question: Where does it multiplex?
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Subject: Re: [MMUSIC] SCTP question: Where does it multiplex?
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Hi Sal,

Salvatore Loreto wrote:
>based on the current stack the SCTP traffic is the only traffic that runs directly
>over the DTLS stack.
>What I am trying to do is to include the Randell Jesup (I am including him in CC
>as I am not sure he is subscribed to this mailing list)
>  suggestion to give the possibility to have multiple SCTP
>*associations* running  on top of the same DTLS session and of course
>providing a way to signal it in SDP.
>to be clear: at moment WebRTC allows only one SCTP association per PC, so
>this is something that would be nice to define just to be ready for the future.

It's a bit unclear to me what the benefit of this would be. SCTP itself allows multiple streams to be transported in parallel within a single SCTP association. So, in what type of situations would we need multiple parallel SCTP associations? I thought the main point of SCTP is that it provides the parallelism and multiplexing by itself.

In other words: I do understand the desire to multiplex RTP and SCTP within the same UDP flow, so we can for instance reduce the number of needed NAT/FW bindings. I also understand why multiple independent non-HOL blocking streams within SCTP are useful for applications. But I don't yet understand the additional benefit of multiple parallel SCTP associations. No doubt it can be technically done, but to what purposes?