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

Christer Holmberg <> Mon, 03 December 2012 08:01 UTC

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From: Christer Holmberg <>
To: Harald Alvestrand <>, "" <>
Thread-Topic: [MMUSIC] SCTP question: Where does it multiplex?
Date: Mon, 03 Dec 2012 08:00:54 +0000
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Subject: Re: [MMUSIC] SCTP question: Where does it multiplex?
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I guess it would be nice to hear from the browser/endpoint people whether they see a need for covering non-RTP in BUNDLE.

If NOT, it would mean a minimum of two 5-tuples, instead of one (one for the bundled RTP media, and one for the data channel).



-----Original Message-----
From: [] On Behalf Of Harald Alvestrand
Sent: 3. joulukuuta 2012 9:54
Subject: Re: [MMUSIC] SCTP question: Where does it multiplex?

On 12/01/2012 07:09 PM, Paul Kyzivat wrote:
> I must say that I am getting confused about what is being multiplexed 
> here. We must be very careful to be precise.
> SCTP defines an *association*, which in simple cases is bound to a 
> 5-tuple. (For now lets not talk about the cases where each end can 
> have more than one address.)
> SCTP multiplexes multiple one-way *streams* over an association. 
> (These are not RTP streams.)
> RTCWEB binds pairs of sctp-streams together into *channels*.

I'm not talking about any of these levels. I'm talking about the reuse of the RTP session's 5-tuple for the DTLS/SRTP 5-tuple, as described in RFC 5764 section 5.1.2.

I said the same thing earlier on this thread (Nov 5), when you first responded (thanks for being the first responder!)

You do make the point that the term "multiplex" is so over-used, it should probably be abandoned altogether - but that section talks about (de)multiplexing, so changing terminology is probably too late for that particular usage.


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