[asterisk-users] Dimensioning

Joshua Colp jcolp at digium.com
Fri Apr 18 08:49:27 CDT 2014

Steve Edwards wrote:
> On Thu, 17 Apr 2014, Jerry Geis wrote:
>> I was thinking transcoding was through PRI card - not gsm to ulaw. :)
> You can convert the GSM files to ULAW using sox. I tend to transcode
> everything to WAV (PCM not that funky 'GSM in WAV') because it is
> relatively cheap (CPU cycles) to transcode from WAV to ULAW and
> everything else in the world understands WAV just fine. If you really
> need to squeeze out every last cycle, you can schedule a script to
> transcode WAVs to ULAWs as needed.
>> So if all I am doing is originating calls, and using playback() in the
>> dialplan - then a system() call on completion I can expect upwards or
>> 3000 concurrent calls?
> Based on my unsubstantiated testing on my hosts, that seems like a
> reasonable conclusion.

I'll just chime in slightly here. At that number of calls you've got 
many factors going on - and they aren't just Asterisk. If playing back 
files you've got disk I/O going on which can slow stuff down (unless the 
system caches it enough or you throw them into a ramdisk yourself). You 
are also sending and receiving a *ton* of small packets. This can make 
network equipment and NICs unhappy.


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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