asterisk users - Sep 2010 - Asterisk as a distributed paging system

I'm building a paging system composed of roughly 10 switches in daisy 
chain, with an embedded box with a speaker and a microphone for each 
switch. The embedded box runs my software.

I need the system to be resilient to any network partition, so that 
anyone can send announces from any mic to all the reachable clients. I'd 
need also to page a subset of all the speakers.

I'm currently using some software I wrote which sends voice over 
multicast RTP and coordinates all the sites with multicast messages.

I don't own the switches so each site will be assigned an address by 
DHCP, that's why I'm using multicast.

I heard of asterisk and SIP as a possible alternative to my software, 
and I'd rather use tested and widely adopted software.

Is there a way asterisk could be of use, or would I need to bend it too 
much?

Thank you in advance,
Matteo

On Wed, 22 Sep 2010, Matteo Fortini wrote:
> I'm building a paging system composed of roughly 10 switches in daisy
> chain, with an embedded box with a speaker and a microphone for each
> switch. The embedded box runs my software.
>
> I need the system to be resilient to any network partition, so that
> anyone can send announces from any mic to all the reachable clients.
I'd
> need also to page a subset of all the speakers.
>
> I'm currently using some software I wrote which sends voice over
> multicast RTP and coordinates all the sites with multicast messages.
>
> I don't own the switches so each site will be assigned an address by
> DHCP, that's why I'm using multicast.
>
> I heard of asterisk and SIP as a possible alternative to my software,
> and I'd rather use tested and widely adopted software.
>
> Is there a way asterisk could be of use, or would I need to bend it too
> much?
It does this as standard.

However, to make it work you need to write some Asterisk dialplan code, 
and have SIP devices (phones) that can auto-answer and go into 
speakerphone mode.

It also doesn't use multicast, so the number of 'speakers' (phones)
you
have might be a limitation. I've tested it with 20 without any issues, 
however as it uses the internal conferernce facilities (meetme), I know 
that there are people out there using asterisk to host some very large 
conferernces, so I suspect for your implementation it won't be an issue...

Your requirement of any to all reachable, even if the network is broken is 
tricky - you might end up having an asterisk box at each switch (which I 
assume is an Ethernet switch) although then you'll have problems with the 
SIP device registrations.

Gordon

With a proper setup and asynchronous dialing, this can be done in a
relatively seamless (although not as simple as this indicates) fashion.

Hi!
> I need the system to be resilient to any network partition, so that
> anyone can send announces from any mic to all the reachable clients.
> I'd need also to page a subset of all the speakers. 
Most of the major phone vendors (that are employed by the users of this 
list) have support for multi-cast of some sort. In recent firmware 
release notes I have read that SNOM has now also added a feature to feed 
multicast directly from a phone (and not just play multicast audio on the 
speaker as long as the phone is not in use).
> I'm currently using some software I wrote which sends voice over
> multicast RTP and coordinates all the sites with multicast messages. 
app_page has been around for quite some in Asterisk, and the new Asterisk 
1.8 now also adds the channel driver "MulticastRTP".
> Is there a way asterisk could be of use, or would I need to bend it
> too much? 
Look here:
http://www.voip-info.org/wiki/view/Asterisk+cmd+Page
http://www.voip-info.org/wiki/view/Asterisk+Paging+and+Intercom

I have made good experience with MAST for multicasting SNOM phones: 
http://www.aelius.com/njh/mast/

Philipp

On 09/22/2010 05:49 PM, Matteo Fortini wrote:
> I'm building a paging system composed of roughly 10 switches in daisy
> chain, with an embedded box with a speaker and a microphone for each
> switch. The embedded box runs my software.
I'm not sure if this is much use to your setup - but I've implemented a 
public announcement system (in UK sometimes called tannoy) using a pc 
and a pair of loud speakers. I used linphonec command line sip client - 
with auto-answer set. This has the disadvantage, of course, that it 
can't be used as a phone as well, to make phone calls from the machine 
driving the speakers (unless you install another sip client) - just as a 
speaker. You might be able to run linphonec on an embedded platform as 
well - with a speaker attached. I know there were some compiled for the 
NSLU2/arm platform already. You will have to combine it with Page() to 
get multiple nodes working at the same time. I only used one.

I did a write-up here - see if you find any useful information:

http://forum.voxilla.com/asterisk-support-forum/asterisk-public-announcement-system-loud-ringer-bell-49339.html

Sebastian
>
> I need the system to be resilient to any network partition, so that
> anyone can send announces from any mic to all the reachable clients.
I'd
> need also to page a subset of all the speakers.
>
> I'm currently using some software I wrote which sends voice over
> multicast RTP and coordinates all the sites with multicast messages.
>
> I don't own the switches so each site will be assigned an address by
> DHCP, that's why I'm using multicast.
>
> I heard of asterisk and SIP as a possible alternative to my software,
> and I'd rather use tested and widely adopted software.
>
> Is there a way asterisk could be of use, or would I need to bend it too
> much?
>
> Thank you in advance,
> Matteo
>