Subject: RE: [AVT] hook-flash

From: John Sirney <[email-masked]>
Date: Fri, 29 Jun 2001 13:23:54 -0500

Chris Fulmer Wrote:
>Why wouldn't this be signalled implicitly -- when you receive a packet with
>a different payload type, it indicates that you're using a new codec.

>This does imply some implementation details on either end -- in effect,
each
>end has to have a codec 'standing by' to accept the new payload.  I suspect
>that only one codec would be needed, as the expected case would be along
>the lines of "I'm doing G.723.1 and now I need to carry fax-over-G.711."
>However, I'd argue that the 2833 approach has the same issue.  In either
>case, you do end up with a problem in negotiation -- if, for example, one
>end tells the other to switch to G.726 and the other end can't do G.726.

It was not received well by our workgroup. The main issue with up speed is
all the equipment between the endpoints must have bandwidth to handle the
change. In the case of Cable Labs,
the CMTS is the keeper of the bandwidth and would have to allocate G711 for
every call thus limiting the total number of lines it can support.  I thing
the problem is more bandwidth than negotiation. Same problem if endpoint can
not up speed to 711.

The interim GR303 to NCS solution diverted this by only allowing G711
communication. 

-----Original Message-----
From: Chris Fulmer [mailto:[email-masked]]
Sent: Friday, June 29, 2001 9:52 AM
To: John Sirney
Cc: [email-masked]
Subject: Re: [AVT] hook-flash

John Sirney wrote:

>
> Some discussion has been proposed to use RFC 2833 to notified between
> endpoints of codec changes without notifing the Call Agent. This was not
> part of the report.

Why wouldn't this be signalled implicitly -- when you receive a packet with
a different payload type, it indicates that you're using a new codec.

This does imply some implementation details on either end -- in effect, each
end has to have a codec 'standing by' to accept the new payload.  I suspect
that only one codec would be needed, as the expected case would be along
the lines of "I'm doing G.723.1 and now I need to carry fax-over-G.711."
However, I'd argue that the 2833 approach has the same issue.  In either
case, you do end up with a problem in negotiation -- if, for example, one
end tells the other to switch to G.726 and the other end can't do G.726.

--
C

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