[Asterisk-Users] Ring more than two isdn phones simultaneously

[Peter Svensson]

On Sun, 21 Aug 2005, Arik Funke wrote:

> If this is a limitation of asterisk, where is it located? In the 
> chan_zap module? In zaphfc? I.e. would it help if I switched to mISDN?

It is inherent in the channel-based structure of Asterisk. An audio 
channel is the basic measure used by applications such as Dial etc. This 
is shared by all channels as far as I know. 

One can imagine a special version of chan_zap that decouples the Asterisk 
channel entities from the actual B-channels. It would always generate a 
new fictitious asterisk channel structure and only link it to a real 
B-channel once the signaling indicated that a B-channel was required. 

I would be interested in how the commercial SS7 implementation for Asterisk 
works. SS7 would normally allow the audio paths to change in mid-call to 
potentially follow an altogether different route.

Peter


> 
> Peter Svensson <psvasterisk at psv.nu> wrote:
> 
> On Sat, 20 Aug 2005, Nico Giefing wrote:
> 
>  >> how many connection do you have from your asterisk to the old pbx?
>  >>
>  >> i think on 1 ISDN connection its only possible to let 2 phones ring, 
> because
>  >> 1 ISDN 2 channels...
> 
> 
> This is a limitation in Asterisk, not ISDN. Asterisk reserves a B-channel
> for each destination at the time of the CONNECT message. In the isdn world
> it is common to not actually allocate a B-channel until it is needed to
> carry audio. This also prevents Asterisk from letting the upstream switch
> select the B-channel on outgoing calls to the pstn.
> 
> Asterisk is written this way since it uses the audio channel as the
> fundamental unit, with the D-channel as carrier of signalling for the
> individual B-channels. Another way to view ISDN is to consider the
> D-channel the fundamental unit, which can carry several audio streams as a
> side effect of the signalling. The first viewpoint resembles the
> traditional view of telephony as individual circuits, the second resembles
> the ISDN/SS7 view of the world.
> 
> Changing Asterisk to be more ISDN-like is quite a lot of work.
> 
> Peter
> 
> 
>  >>
>  >> ----- Original Message -----
>  >> From: "Arik Funke" <arik.funke at gmx.de>
>  >> To: <asterisk-users at lists.digium.com>
>  >> Sent: Saturday, August 20, 2005 7:44 PM
>  >> Subject: [Asterisk-Users] Ring more than two isdn phones simultaneously
>  >>
>  >>
>  >
>  >>> > I am using a HFC-S card in nt mode with zaphfc driver to connect an
>  >>> > internal isdn bus. I would like to signal an incoming call on, let's
>  >>> > say, 4 phones. Right now I use:
>  >>> >
>  >>> > Dial(Zap/g1/21&Zap/g1/22&Zap/g1/24&Zap/g1/23&Zap/g1/29,,t)
>  >>> >
>  >>> > where g1 are my two isdn channels provided by HFC-S card an the
>  >>> > 21,22,etc my internal numbers.
>  >>> >
>  >>> > When the command is executed however, only the first two specified
>  >>> > phones ring. Etc. with the first channel 21 ist called, with the 
> second
>  >>> > 22. How can I get asterisk to signal to all phones with just one isdn
>  >>> > channel? I am trying to duplicate the setup I had with my old 
> isdn pbx
>  >>> > with did above trick just fine... Maybe somebody can help me 
> configure
>  >>> > asterisk appropriately?
>  >>> >
>  >>> > Cheers,
>  >>> > Arik
>  >>> >
>  >>> >
>  >>> > PS: I gave following a try but without success:
>  >>> > Dial(Zap/g1/21-29,,t)
>  >>> > Dial(Zap/g1/21+29,,t)
>  >>> > _______________________________________________
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>  >>> >
>  >
>  >>
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> 
> 
> Peter