Subject: [Megaco] Resource availability

From: Rajesh N <[email-masked]>
Date: Wed, 13 Mar 2002 10:24:23 +0530

Hi,

A media gateway may support codecs A,B,C,D. Is the MGC application expected 
to do an audit on MG  and understand the codecs supported by MG??

Once MGC is aware of MG's media processing capabilities, it can use its 
intelligence to specifiy the appropraite codec value in SDP part of 
Local/Remote descriptors.

Could someone explain this process?

Regards,
Rajesh N

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From: "Rosen, Brian" <[email-masked]>
Date: Wed, 13 Mar 2002 08:11:53 -0500

> to do an audit on MG  and understand the codecs supported by MG??
Yes
 
> intelligence to specify the appropriate codec value in SDP part of 
Correct
 
> Could someone explain this process?
For simple cases (static, not load dependent codec support), the
MGC audits the MG, discovers what codecs it can support and then
either chooses by local (MGC) policy, or by negotiation with 
another signalling endpoint what codec will be used for a particular
context.  The MGC then uses MEDIA to specify what codec the
MG should use.

Some MGs have more complex resource models.  A common case is that
with no active calls, the MG may have 3 or more codec choices, but
as calls become active, the DSP that is implementing the codecs
either runs out of memory or cycles to support all choices.

In these cases, the MGC asks the MG (by construction of the MEDIA
descriptors) to specify its current capabilities.  The MG would
construct a response MEDIA that contains the choices it can sustain
at that time. The MGC would later MODIFY the MEDIA descriptor based
on policy or negotiation.

Brian

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From: "Rosen, Brian" <[email-masked]>
Date: Wed, 13 Mar 2002 08:11:53 -0500

Yes
 
Correct

Brian

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From: "Miao, Kai" <[email-masked]>
Date: Wed, 13 Mar 2002 09:41:53 -0500

Brian,

How realistic then for a MG to support multiple codecs in a single call? Is
it true that practically all MGs only uses one particular codec in a single
call? 

Both H323 and SDP have the ability to specify more than one codec for a
single call, are there any practical cases where such ability ever get used?

Kai Miao
Intel

-----Original Message-----
From: Rosen, Brian [mailto:[email-masked]]
Sent: Wednesday, March 13, 2002 8:12 AM
To: 'Rajesh N'; [email-masked]
Subject: RE: [Megaco] Resource availability

Yes
 
Correct

Brian

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From: "Miao, Kai" <[email-masked]>
Date: Wed, 13 Mar 2002 09:41:53 -0500

Brian,

Kai Miao
Intel

-----Original Message-----
From: Rosen, Brian [mailto:[email-masked]]
Sent: Wednesday, March 13, 2002 8:12 AM
To: 'Rajesh N'; [email-masked]
Subject: RE: [Megaco] Resource availability

Yes
 
Correct

Brian

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From: "Rosen, Brian" <[email-masked]>
Date: Thu, 14 Mar 2002 10:28:26 -0500

Megaco does not alter the ability of SDP to describe multiple codecs
for a single call.  The usual example is a compression codec like
G.726 and DTMF-in-RTP.

Brian

> From: Miao, Kai [mailto:[email-masked]]
> Sent: Wednesday, March 13, 2002 9:42 AM
> To: 'Rosen, Brian'; 'Rajesh N'; [email-masked]

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From: "Rosen, Brian" <[email-masked]>
Date: Thu, 14 Mar 2002 10:28:26 -0500

Brian