Re: [MMUSIC] Single SCTP usage per SDP session?

[Christer Holmberg <[e-mail]>]

Hi,

>>> Per my understanding, draft-ietf-tsvwg-sctp-dtls-encaps just talks about SCTP over DTLS and allowing multiple SCTP associations, which is perfectly fine.
>>> Then it is possible to come up with SCTP-SDP semantics to use that capability.
>>> One m= line allowing one SCTP over DTLS limit is fine. Using BUNDLE 
>>> you can replicate same 4-tuple in multiple m= lines. Then there is only one DTLS association established and multiple SCTP associations over that is possible (one per m= line).
>>> If BUNDLE is not used then I believe same 4-tuple on multiple m= 
>>> lines are NOT possible. This is because, per my understanding, unlike TCP/native-SCTP used under non- ICE environments, in ICE-environments the TCP/UDP port specified is used both as client and server port for DTLS.
>>
>> Even with BUNDLE, you would have to use the same m= line port value from the beginning, which is not allowed. So, you basically would have to add the additional SCTPoDTLS m= lines once the usage of BUNDLE has been negotiated.
>
> bundle-only would allow you to set this up.

Correct.

But, then we would need to have rules saying that you are not allowed to move an m= line associated with a SCTP usage out of the BUNDLE group, etc.

Regards,

Christer