Re: Selection of media (m=) at MG

Hello Albrecht,

I agree in general.

However, I have a doubt about ISDN/SIP interwork spec [ETSI TS 183 036]. 
This spec. proposes that in the Q.931/SIP interworking, some EIs Q.931 
are codec to SDP and/or inserted in the SIP body as a PSTN XML element.

Under what criteria, an Q.931 EI should be?:

(a) Codec to SDP

AND / OR  (this is also important)

(b) Inserted in the SIP body as a PSTN XML element

or

(c) None (only interpreted by the AGW, without being carried over SIP)

Regards,

Javi



El 30/11/2011 8:34, Schwarz, Albrecht (Albrecht) escribió:
> I'm not familiar with the ISDN/SIP interwork spec [ETSI TS 183 036], but I guess that this could be the emulation of ISDN bearer service "UDI with support of tones/announcements" [ITU-T I.231.x].
> The (optional?) capability of tones/announcements is just required during the call establishment phase, - before the communication phase.
>
> 1st Dependency on MG type
> 	a) TGW: no impact, because tone/announcement inserted by ISDN local exchange (terminating Q.931); TGW needs just clearmode support
> 	b) RGW/AGW [ETSI 183 002]: ... call-dependent procedures for specifying the details of the emulation service
>
>
> 2nd H.248 RGW/AGW profile [ETSI 183 002]
> You don't find correspondent call dependent procedures, also due to historical reasons because this was the very first profile defined before the "ITU-T H.248 profile template" was developed.
> On the other side, it could be transparent for the MG as you said.
>
> E.g., MGC
> ->  call establishment phase: IF tones/announcements THEN H.248 Command.req for tone/announcement control plus media configuration with voice codec
> ->  after: H.248 Command.req for modification of the media configuration towards CLEARMODE
>
> Thus, two media configurations in time series.
>
> Regards
> Albrecht
>
> PS
> My experience: the condition "IF tones/announcements" AND "ISDN bearer service UDI" seems to be very, very rare, thus just starting UDI bearer service emulation in CLEARMODE ...
>
>
>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of Javi Muñoz
>> Sent: Dienstag, 29. November 2011 18:40
>> To: [email protected]
>> Subject: [Megaco] Selection of media (m=) at MG
>>
>> For the ISDN UDI-TA capability, [ETSI TS 183 036] proposes to
>> describe the media at MG using the next SDP description in
>> the Local/Remote
>> descriptors:
>>
>> m=audio<puerto>  RTP/AVP<Dynamic_PT>  0 [8]
>> a=rtpmap:<Dynamic_PT>  CLEARMODE/8000
>>
>>
>> MG must use the codec:
>>
>> * CLEARMODE: in the phase of the call of information transfer.
>>
>> * Audio Code G.711-u/A: in the phase of the call of
>> establishment/release.
>>
>>
>> The phase of the call is known by the MGC (using signalling
>> Q.931, not visible to the MG). But, with that SDP
>> description, how may MGC indicate to the MG which codec may
>> use at each instant?
>>
>> Regards,
>>
>> Javi
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