Subject: RE: [Megaco] interpretation of H.248.23 andisp package andthedwa /data signals

From: "Wayne Cutler" <[email-masked]>
Date: Fri, 29 Apr 2005 09:07:11 +0100

Hi Dal,

Some comments/observations in-line. 
 
>From reading the e-mails there appear to be two different approaches for 
providing "On-Hook" display associated with ringing using the H.248 
"andisp" package. 
 
One approach assumes that the TAS signal is determined/provisioned within 
the MGC (i.e. andisp/data) and the other approach that assumes the TAS 
signal is determined/provisioned in the MG (i.e. andisp/dwa).
 
WC - Yes, you can provision the MGC or the MG. Both cab be made to work. 
It is a philosophical argument. 

I can understand why a number of implementations have adopted the former 
approach, because it provides a single and consistent mechanism for 
delivering "On-hook" display "during ringing", "prior to ringing" and "not 
associated with ringing". Moreover it means that a single signal 
"andisp/data" can be used for delivering all variants of the "On-Hook" and 
even the "Off-Hook" display service. 
 
WC - Yes, andisp/data can be used for the whole lot if desired. 

If the latter method is used, then it means the two different signals must 
be used. The signal "andisp/dwa" for "On-Hook" display associated with 
ringing. The signal "andisp/data" for "On-Hook" display not associated 
with ringing. Also the TAS signal for the "andisp/dwa" case is 
determined/provisioned within the MG, while for the "andisp/data" case the 
TAS is determined/provisioned within the MGC.  This does mean things are 
modelled differently for the two cases and this does seem to be an odd 
approach and incorrect from a service modeling and provisioning 
perspective.
 
WC - Yes. It is less consistent. 

We can either try to mandate that "andisp/dwa" is used for "On-Hook" 
display prior to and during ringing, but there appears to be a lot of 
benefits and mileage in allowing "andisp/data" to be used for "On-Hook" 
display prior to ringing, during ringing and not associated with ringing? 
especially since a number of implementations have already adopted this 
approach.
 
 WC - There seems to be a lot oif options in this area (and a number of 
implementations) and this is why the TISPAN profile shopuld be open and 
allow 
national operators (if they so wish) to decide between options. 

Regards,

Wayne 

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