Re: [MMUSIC] SCTP-SDP: Virtual Connection impact

[Roman Shpount <[e-mail]>]

On Thu, Apr 2, 2015 at 4:57 PM, Paul Kyzivat <[e-mail]> wrote:

> Well, when using SIP replace the session-id (o-line) should change. And it
> is supposed to remain unchanged within a dialog.
>
> So from an SDP perspective a totally new session-id value can be taken as
> an indication. But this affects the complete SDP session, not just a single
> m-line or bundle.
>

There are also third party call control scenarios where media from several
different agents is aggregated into a single SDP session. One example would
be a solution where audio conferencing server and video SFU are aggregated
to appear as a single solution using a separate signaling agent. Using
entire new session id will not work in such case, since DTLS connection for
only one of the media lines might need to be re-established with the other
m= lines reusing existing connections.


> ISTM that a=connection:new is the better answer. The forbidding of this
> for SRTP-DTLS seems like a bug rather than a feature. Does anyone know the
> reason for it?
>

I do agree a=connection:new is the better answer. One problem that I see
with it, that it re-establishes all the protocols running on the same m=
line which support it. For instance if you have SCTP and DTLS used on the
same m= line, both will be reset when a=connection:new is specified. I am
not sure how big of the problem this is for SCTP or other protocols and if
you would ever need to re-start SCTP without restarting DTLS or vice verse.
_____________
Roman Shpount