Subject: RE: [Megaco] LCN mapping

From: "Tom-PT Taylor"<[email-masked]>
Date: Tue, 15 Jan 2002 12:37:55 -0500

The short answer is that the relationship between LCN (Logical Channel
Number) and streamID is set by the application control, which probably
resides in the MGC.  Assuming your H.223 mux is operating as part of the
H.324 system it was designed for, the control information is carried in
H.245 signalling, gets routed to the MGC, and results in H.248 requests back
to the MG.

However, let me first address your proposed multiplexing structure.  I
should mention that several of us (Christian Groves, Roni Even, Marcello
Pantaleo and myself) are nearing the end of a discussion initiated by
Christian, on additional words to add around the multiplex concept,
clarifying it and at the same time allowing it to be used to represent Nx64K
wideband service.  I will report the results and reasoning to the list
shortly.  In any event, the basic multiplex concept I have been defending
(based on what we already have in RFC 3015/H.248)is something that
specifically has one or more circuits on one side and appears as an ordinary
termination to the rest of the context on the other.  Along the way, it
hides the circuits (which are represented by terminationIDs of their own)
from the rest of the context.

In your present example, you have the multiplexing termination (T3), 30 or
24 circuits which support it (the circuits in the E1/T1), and the RTP
termination T2.  If you are running H.324, the recommended way to tie the
circuits together is to use H.226 channel aggregation (set up with V.140
signalling) under the H.223 multiplex.  Because H.226 is mentioned in H.324
(Annex F) but not in H.223, I suspect we have to model the two layers of
multiplexing explicitly.  This blows holes in my idea that all multiplexes
are supported directly by circuits.  In diagramatic terms, we have the
following situation:

                        Context interior ---->
                    _________                 _________
       Data stream  | H.226 |                 | H.223 |   Audio stream
Ckt 1 ..............| "MUX" |                 |  MUX  | .................
       . . .        | term  |   Data stream   | term  |
       Data stream  |       | ................|       |   Video stream
Ckt n ..............|       |                 |       | .................
                    |       |                 |       |
                    ---------                 ---------

Here the H.226 MUX termination contains/is supported by the individual
circuits, which appear as terminations in their own right.  The H.223 MUX
termination contains/is supported by the H.226 MUX termination.

The model I have been arguing for is that a multiplexing termination hides
all of the terminations it contains from the rest of the context.  One
implication of this is that the streamIDs of the streams flowing between the
contained terminations and the multiplexing termination are local rather
than global in scope.

Looking at the above diagram, people may ask how we know that the stream
between the H.226 and H.223 multiplexing terminations is a data stream,
while the streams passing from the H.223 termination to the rest of the
context are audio and video.  I will maintain that this is a result of the
definition of the respective multiplexes.  If this is not clear, we need an
explicit description of the exterior-side and context-side streams supported
by each multiplex somewhere within our Megaco/H.248 documentation.

I come to my final point.  Your example included the RTP termination T2
within the multiplex.  In my view this is a mistake: T2 is just another
termination in the context.  All it sees is T3, the H.223 multiplexing
termination, and it exchanges audio and video with that termination.

I hope this makes things clearer.  The question has raised some points which
I will now have to reflect back into my conversation with Christian and all.
Even better if they bring that conversation to this list.

-----Original Message-----
From: Christer Holmberg [mailto:[email-masked]]
Sent: Tuesday, January 15, 2002 2:28 AM
To: [email-masked]
Subject: [Megaco] LCN mapping

Hi,

I have a question related to H.223 multiplexing.

Assume that I have one E1/T1 termination (T1) and one RTP termination
(T2). The RTP termination has two streams, one for audio and one for
video (I could also have separate terminations for each RTP stream).

Then I also add a multiplexing termination (T3), and in the
MuxDescriptor I define that T1 and T2 shall be multiplexed.

My question is: how do I define that a specific H.223 LCN is multiplexed
into a specific H.248 stream? Can I assume that this will be done if I
use the same value for the StreamId and the specific LCN that stream
shall be mapped into?

Regards,

Christer Holmberg
Ericsson Finland

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