I am using the paging module to broadcast an alarm message to all SIP phones during a fire alert.
So someone dials a paging group number and all phones auto answer (or via chanspy whisper if on a call) and play an announcement “fire alarm…”.
The announcement is about 5 minutes long, always looping a simple sentence.
I am only interested in the announcement, not in the intercom feature, where all called parties would hear the caller. As it’s fire alarm, the initial caller places the call, doesn’t hang up and runs out of the building.
I have about 60 phones and a reasonably powerful server (surely able to handle 60 simultaneous calls). Had to increase the maximum page group members from 40 to 60.
Is above implementation a workable solution or would you recommend a different approach?
Multicast paging seems a better fit for this number of people. Although you say your server won’t have a problem with 60 concurrent calls. In this case you would need to combo the PagePro module with your announcement and the multicast paging.
Be careful no matter which way you implement this that you don’t have “Broadcast Storm Protection” (HP) or whatever it’s called on your switches - Older HP’s are kind of sensitive to it, and you can end up in a situation where you start a page, and then you can no longer talk to your endpoints until the “protection” times out.
REALLY bad in an emergency situation like a school “Lock-down” event.
I will surely look into multicast, but I haven’t completely ruled out using non multicast paging/intercom as I would also like to include a few extensions on a remote system connected via SIP trunk.
What is it exactly that would speak against using paging/intercom the regular way on up to 60 extensions?
What problems, performance issues can I expect?
I know it would be 60 full simultaneous calls, but that in itself shouldn’t be much of a problem I suppose with the reasonably powered server we have, should it?
The school I referenced above is 57 Yealink T42G’s and T48G’s - Paging to them is not a problem, but like I say, make sure you test it in a off-hours manner before you try it for real and have a problem.
The simultaneous setup of all the calls is going to spike your CPU. After that, the transmission of the call through the extension interface is probably going to spike the CPU again. It may work, it may even transmit the call data, but I doubt it’s going to be "light weight’ enough to actually make it through the interface with 60 instances trying to set up and transmit at the same time.
There are ways you could do it, including breaking the call setup and transmission over several sessions, but 60 calls at once if probably going to overwhelm the processor.
One solution if multicast is not an option might be to create 60 callfiles that are touched (you can use sub-second granularity) randomly over the next NN seconds and sent to *80${EXTEN(S)} using application and data=your recording , if the phones support it (Been There Done That)
While your CPU may sustain 60 or even 200 ongoing calls, I wouldn’t expect it to be able to make 60 SIP calls simultaneously and then send a sound file simultaneously to 60 endpoints.
That’s why multicast has been introduced and is supported by all SIP endpoint vendors.
As this is a fire alarm, you don’t need to broadcast it to remote offices - the fire alarm is only valid for that building.
It’s the endpoint that broadcasts the message to the others on that network, not Asterisk, and you can set up many different channels to create extension groups.
However, as you need to play a prerecorded message and not to broadcast a live announcement, you may need to write something directly in the dialplan that does the multicast from Asterisk and broadcasts a special Music on Hold category with that message.
I would have to agree with the multicast option - the setup for the calls to 60 endpoints is going to cause a delay, and if you have anything like reception BLF’s they are going to light up like crazy whenever you page.
If you would rather dial an extension to page, you can get a SIP paging device like an Algo 8180 and have it push the multicast page. You could also use one at your remote location to setup a multicast page there as well, all done by dialing a paging extension number.
