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

[Paul Kyzivat <[e-mail]>]

On 12/3/12 2:53 AM, Harald Alvestrand wrote:
> 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.

These are all related. We are making even more of a mess of SDP than it 
already is by patching on a new hack for each sort of multiplexing 
somebody comes up with. But focusing on just this:

How do you imagine this multiplexing will be signaled in SDP?
The obvious way would be to bundle the DTLS/SCTP m-line with the RTP 
m-lines. But that will violate the rule that all the bundled m-lines 
have the same <proto>. (And there is an even worst fit between this and 
mmt.)

	Thanks,
	Paul