Re: [MEDIACTRL] Direct Phone Call Call-Flow

["Rusu Andreea-B00553" <Andreea.Rusu at freescale.com>]

Hi,

I do agree with you that MEDIACTRL should not address the DSP
allocation/management business. The Media Server alone is responsible
with this.

What I am suggesting is to allow the Media Server to renegotiate the
connection settings (maybe even codecs) for a certain media connection.
For example, if one connection was created with an INVITE received from
AS, later on the MS should be able to send a re-INVITE for the same
connection to change the IP address or UDP port on his side.

There may be situations when the Media Server needs to perform
internally some resources re-allocations (for load balancing or for
optimizations) which would require changes in the connection settings of
a certain media connection (the scenario presented in the initial email
is such an example). Another plausible scenario is when one DSP stops
and the Media Server is recovering by restoring the media connections to
a new DSP (another network entity). This could have the side effect of
changing the IP addresses of the restored connections.

With H.248 the context is first created and then the terminations are
added to that context. So the Media Gateway could easily allocate the
terminations belonging to the same context on the same network resource.

With MEDIACTRL the media connections are created first and then they are
joined together or with a mixer. Even if the mixer is created before the
media connections, as far as I know, there is no way for the Media
Server to know that the media connections will be joined later with that
mixer or another. 
So, I do agree that the AS should not tell MS where to create the
connections but in case MS needs to move some connections internally
from one network entity to another it should be able to announce the AS
of this change. 

The MEDIACTRL standards are not forbidding or allowing the renegotiation
(re-INVITE) of a media connection by a Media Server. I believe this
could create interoperability problems and it would be useful to be
clarified.


Andreea Rusu

-----Original Message-----
From: Eric Burger [mailto:eburger at standardstrack.com] 
Sent: Tuesday, August 11, 2009 9:26 PM
To: Rusu Andreea-B00553
Cc: mediactrl at ietf.org
Subject: Re: [MEDIACTRL] Direct Phone Call Call-Flow

Step 6 is totally behind the curtain. MEDIACTRL explicitly will not get
to the DSP allocation / management business.  Even H.248 will not allow
for that level of control.

That said, an intelligent controller should be able to figure out if you
allocate the mixer first, then maybe everything should be on the same
DSP.

On Aug 11, 2009, at 8:24 AM, Rusu Andreea-B00553 wrote:

> Hi,
>
> I have been studying the mediactrl drafts lately and I have the 
> following question.
>
> Is  the scenario described below for a direct phone call valid from 
> the mediactrl framework perspective? This scenario is based on the 
> call flow presented in the draft-ietf-mediactrl-call-flows-01 draft 
> from chapter 6.2.1 Direct Connection.
>
>     1) AS requests MS to create a media connection for UAC1 using SIP 
> Signaling.
>     2) MS allocates resources for the UAC1 connection on one DSP 
> device.
>     3) AS requests MS to create a media connection for UAC2 using SIP 
> Signaling.
>     4) MS allocates resources for the UAC2 connection on another DSP 
> device (e.g. there is no room left on the previous DSP).
>     5) AS requests MS to join UAC1 connection with UAC2 connection 
> using the Control Channel.
>     6) MS can join the connections only if they are located on the 
> same DSP. By reducing the internal media traffic between two DSP
> devices the I/O         processing on the DSP is also reduced thus  
> allowing more external media streams to be handled with the same 
> processing power. So MS decides to move the media connection of UAC1 
> to the second DSP. In this case the media IP Address and/or the UDP 
> port for the UAC1 connection will change. MS needs to inform AS of 
> this change by sending a re-INVITE.
>         Once the re-Invite is accepted by AS, MS will join the two 
> connections and acknowledge the Join command on the Control Channel.
>
> If this is a valid scenario, should it be specified in the standards 
> that the MS can renegotiate the connection settings (maybe also
> codecs?) after a media connection was already created?
>
> Thank you in advance,
> Andreea Rusu
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