Re: Selection of media (m=) at MG

Albrecht,

I complete my comment "(b)":

[ETSI TS 183 002 Clause 7.1.4]
Access Gateways may be able to store recorded announcements and shall 
support the generic announcement package. Generic Announcement (ITU-T 
Rec. H.248.7 [18]): mandatory if local announcements are available.
When the announcement to be delivered is not available in the gateway 
and cannot be autonomously retrieved by the gateway from a remote 
repository, the MGC shall initiate a connection to an external 
announcement machine, by temporarily adding a termination into the 
context. Instructions to play announcements are sent directly from the 
MGC to the server. The announcement server may itself be implemented as 
an MG, controlled using the H.248 protocol. However, this interface is 
outside the scope of the present document. In an originating MG, the 
context topology and the termination modes shall be configured in such a 
way that in-band information can be received from the remote side before 
the called party's answer. This setting shall occur not later than the 
receipt of the ACO message (or an equivalent message from another 
signalling protocol that ISUP).

Regards,

Javi
>
>> well spotted, thus just a single media configuration ('Clearmode') 
>> would be already sufficient to emulate that ISDN bearer service
> However, two comments:
>
> (a) In the "call establishment phase": what must be created at the 
> MG?: would it be necessary to create a context, or would it be enough 
> to create only an ISDN termination in the null context (which would 
> generate that tone/announcement, and then, MGC would apply a modify 
> command to create the context for the information phase)?
>
> (b) I believe, the announcement do not necessarily have to be recorded 
> in AGW, but that may come from an announcement server (I guess this 
> would also be possible for DTMF tones). Could this justify the 
> creation of such IP termination with voice codec G.711 in the 
> establishment phase, or that communication with the announcement 
> server does not belong to the ISDN call and, therefore, it should not 
> be involved in its Megaco context?
>
> Regards,
>
>
>
>> PS
>> Your previous email was related to ISDN-to-SIP interworking at call 
>> control level, a subject which is out of scope of MEGACO.
>> Thus, something for SIPPING, SIP-IMPLEMENTERS, ... (or TISPAN WG3 
>> list) in my understanding.
>>
>>> -----Original Message-----
>>> From: Javi Muñoz [mailto:[email protected]]
>>> Sent: Mittwoch, 30. November 2011 18:13
>>> To: [email protected]
>>> Cc: Schwarz, Albrecht (Albrecht)
>>> Subject: Re: [Megaco] Selection of media (m=) at MG
>>>
>>> A second comment,
>>>
>>> If:
>>>>>      a) TGW: no impact, because tone/announcement inserted by ISDN
>>>>> local exchange (terminating Q.931); TGW needs just
>>> clearmode support
>>>
>>> (I agree)
>>>
>>> then, why?
>>>>> E.g., MGC
>>>>> ->   call establishment phase: IF tones/announcements THEN H.248
>>>>> Command.req for tone/announcement control plus media configuration
>>>>> with voice codec
>>> That "media configuration with voice codec" (G.711) would be
>>> done at the MeGaCo termination of the IP side of the MG, not
>>> at the termination of the ISDN side. If tone/announcement is
>>> inserted (in the UNI ISDN) by this MG, the termination of the
>>> IP side of the MG would not be used, so that "voice codec"
>>> would not be relevant (no media would be transported over the
>>> IP network).
>>>
>>> am I wrong?
>>>
>>> Regards,
>>>
>>> Javi
>>>
>