asterisk users - Jul 2015 - How may SIP 183 messages a caller receives when many callee rings?

Hi.

I have a beginner conceptual question about Asterisk:

Let's suppose that there are 4 softphones registered in my Asterisk and all
of them are currently online. In addiction , there is no call.

Suddenly, one of these softphones  sends a SIP message to the Asterisk. In this
case the dialplan will execute the instruction  ' exten =>
2005,1,Dial(SIP/2000&SIP/2001&SIP/2002, 30) '

All softphones (2000, 2001 and 2002) will ring. These are proprietary softphones
and all of then will reply with SIP 183 message. SIP 183 will contain SDP with
media information.

The question is:

Will the caller receive SIP 183  from each callee? That is, will it receive 3
SIP 183 messages? It is important to the caller receives a SIP 183 message from
each callee, because this caller needs to send early media (video) to every
callee.

Or, will Asterisk send just one message SIP 183 to the caller, with some kind of
generic SDP message?

Any hint will be very helpful!

Thanks a lot.


RODRIGO PIMENTA CARVALHO
Inatel Competence Center
Software
Ph: +55 35 3471 9200 RAMAL 979     (Brasil)

Rodrigo Pimenta Carvalho wrote:
> Hi.
>
> I have a beginner conceptual question about Asterisk:
>
> Let's suppose that there are 4 softphones registered in my Asterisk
> and all of them are currently online. In addiction , there is no
> call.
>
> Suddenly, one of these softphones  sends a SIP message to the
> Asterisk. In this case the dialplan will execute the instruction  '
> exten =>  2005,1,Dial(SIP/2000&SIP/2001&SIP/2002, 30) '
>
> All softphones (2000, 2001 and 2002) will ring. These are proprietary
> softphones and all of then will reply with SIP 183 message. SIP 183
> will contain SDP with media information.
>
> The question is:
>
> Will the caller receive SIP 183  from each callee? That is, will it
> receive 3 SIP 183 messages? It is important to the caller receives a
> SIP 183 message from each callee, because this caller needs to send
> early media (video) to every callee.
>
> Or, will Asterisk send just one message SIP 183 to the caller, with
> some kind of generic SDP message?
Asterisk isn't a proxy, so it won't forward all 3 and it won't
forward
media from all 3. Right now the Dial application is simple and just 
doesn't forward media in this scenario.

-- 
Joshua Colp
Digium, Inc. | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org

Hi Joshua Colp.

Thank you very much for alerting me about the impossibility of forwarding the
SIP 183 messages from callees to caller, via Asterisk, when more than 1 callee
ring at same time.

In my project the caller software (a proprietary softphone) needs to know some
information about the callees, while they are still all ringing. Such
information will be used to create early media (only video) from caller to all
callees. For example, the caller softphone should receive the IPs and ports
where each callee will listen to video data. The caller softphone will use RTSP
to create such early media. That is why I was investigating an way of passing
SIP 183 messages from callees to the caller.

However, as you told me about such impossibility, now I have to discover a way
of collecting such callees' media information and deliver it to the
proprietary caller software.
So, I ask you:

1 - Is there a way of collecting information from SIP messages that arrives in
Asterisk, in dial plan (by means of application  or functions)?  If yes, I could
pass it to a external software.

2-  Is there a way of handling SIP 183 or SIP 180 messages in dial plan and
forward such messages to another destiny, as in a proxy?

3 - Should I use Asterisk REST Interface to collect information from SIP
messages that pass in the current channel of a call, whether I need collect it
and pass to a proprietary software? I was reading about ARI today.

4 - By the way, can an external application, using ARI, send requests to the
Asterisk, even when such application is not invoked by a dial plan? That is, can
an external application decide by itself to contact a Asterisk REST interface?

Any hint about early media (video) with asterisk will be very helpful to me, as
I'm completely beginner in this field.

Thanks a lot!


RODRIGO PIMENTA CARVALHO
Inatel Competence Center
Software
Ph: +55 35 3471 9200 RAMAL 979  (Brasil)
________________________________________
De: asterisk-users-bounces at lists.digium.com [asterisk-users-bounces at
lists.digium.com] em Nome de Joshua Colp [jcolp at digium.com]
Enviado: quarta-feira, 8 de julho de 2015 11:53
Para: Asterisk Users Mailing List - Non-Commercial Discussion
Assunto: Re: [asterisk-users] How may SIP 183 messages a caller receives when
many callee rings?

Rodrigo Pimenta Carvalho wrote:
> Hi.
>
> I have a beginner conceptual question about Asterisk:
>
> Let's suppose that there are 4 softphones registered in my Asterisk
> and all of them are currently online. In addiction , there is no
> call.
>
> Suddenly, one of these softphones  sends a SIP message to the
> Asterisk. In this case the dialplan will execute the instruction  '
> exten =>  2005,1,Dial(SIP/2000&SIP/2001&SIP/2002, 30) '
>
> All softphones (2000, 2001 and 2002) will ring. These are proprietary
> softphones and all of then will reply with SIP 183 message. SIP 183
> will contain SDP with media information.
>
> The question is:
>
> Will the caller receive SIP 183  from each callee? That is, will it
> receive 3 SIP 183 messages? It is important to the caller receives a
> SIP 183 message from each callee, because this caller needs to send
> early media (video) to every callee.
>
> Or, will Asterisk send just one message SIP 183 to the caller, with
> some kind of generic SDP message?
Asterisk isn't a proxy, so it won't forward all 3 and it won't
forward
media from all 3. Right now the Dial application is simple and just
doesn't forward media in this scenario.

--
Joshua Colp
Digium, Inc. | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org

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