Decided and Determined texts

Joerg Ott jo at TZI.UNI-BREMEN.DE
Fri Jun 4 03:52:04 EDT 1999

In order to give an example of why it is of importance for the MGC to know
what type of modem connection that was activated, I provide a first draft
of how text telephone support can be explained in H.gcp . 
In this case the modem will indicate V.18 usage, and that means that the
media stream will be a T.140 text stream. 

In the T.38 case it will be some kind of fax data stream, while for the
V.90 case, I hope that the idea would be to use it for a PPP session to
access the Internet. 

So, these three modem types need quite different actions from the gateway
and it need to be reflected in the MGC interface.

Please look in the attached proposed new section to H.gcp for further
discussion and explanation.

Can anyone look into how to structure alternating between voice and text on
the SCN side during a call and leading text to the text stream and voice to
the audio stream on the IP side?  ( called "voice over" in USA ) Can we
support it? 


Gunnar Hellström

At 11:05 1999-06-03 -0700, you wrote:
>At 12:19 PM 6/3/99 -0500, Nancy-M Greene wrote:
>>> > >Modem type: none, V.90, T.38, V.18, ... as applicable.
>>>> Why is this passed from MGC to MG?  What does the MG do with it?  Isn't
>>>> this an MG capability?  Maybe this is only useful for audit.
>>>[[TomT]] This information is probably only useful for H.324 calls, although
>>>maybe it also applies to NAS operation.  The MGC knows which modem type to
>>>assign based on dialled number, and passes the information to the MG to act
>>Yes, this information is useful for NASes. In the SS7 case, the MGC knows
>>which physical circuit the call will be completed on, and based on the
>>dialled number, may have modem characteristics that need to be given to the
>>NAS (MG) before that call is completed.
>As has been discussed quite a bit before, this is AAA info and NAS's
>already have a protocol for that. We don't need to reinvent the wheel.
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Gunnar Hellstrom
LM Ericsson

E-mail gunnar.hellstrom at
Tel +46 751 100 501
fax +46 8 556 002 06

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