[asterisk-users] Asterisk concurrent calls count

[Sherwood McGowan]

Alexander Olekhnovich wrote:
> Hi Asterisk Users,
>
> I'm interested in how many concurrent calls Asterisk can process 
> without troubles. I mean 1 Asterisk server (software) like either 
> proxy or media server (any numbers will be appropriate).
>
> 1. Is there any limitations by the software? What is this number?
> 2. What is the maximum count of concurrent calls you've ever seen/tested?
>
> -- 
> Thanks in advance
> Alexander Olekhnovich
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Rather than jump into the heavy list of replies, in which there's some 
heated discussion, I thought I'd offer a quick $0.02:

Asterisk's concurrent call capabilities is limited (as far as I know) 
only by the hardware you're using and the implementation. By this I mean 
that the amount of transcoding, meetme conferences, SIP/IAX/Zap 
channels, recording, CDR backend, etc...all take their toll on your 
hardware's capabilities.

I'll give you two examples:
1. On a Dual 1.5Ghz XEON, 2GB RAM server running CentOS 4.5(unsure on 
this anymore) with only Asterisk 1.4 TRUNK in 1995 in a SIP only 
environment with ONLY ulaw encoding, I've seen 500+ concurrent calls 
with over 2K users on a single machine. All clients were set for 
canreinvite=no, and qualify=yes. This system did not show degradation of 
performance.

2. I'm currently working with a client that has a Dual 2.5 Ghz, 2GB RAM 
server, running Debian Etch. They are running two EM Wink T1 Trunks, and 
51 Zap phones locally running through Adtran Total Access Channel Banks, 
12 POTS lines running through a Rhino channel bank, and 27 SIP Phones. 
Concurrent calls only run at around 43 calls currently, although I've 
seen it as high as 53, and ALL calls are recorded other than local 
spying on channels and inter-extension calls. Additionally, this server 
has PostgreSQL and Apache running on it to allow administration to 
review CDRs and pull recordings, and a Zabbix monitoring agent daemon 
sending data to a local network Zabbix server.  This server showed 
little or no degradation in call quality or service (even with Sox and 
Speexmix running in the background converting recordings via a 
background script) until just recently when we changed T1 providers and 
got EM Wink instead of the requested PRI. Before we had 99.999% of all 
calls complete from dial to hangup with no issues. Now we're at 98.8%, 
with calls being dropped in midconversation. I have not found the answer 
to what is causing the server to drop calls, other than after the 
switchover to EM_W our Zaptel accuracy started degrading. We are in the 
process of figuring out how we can resolve this, including possible 
hardware upgrades (which were already planned for handling recordings 
better)

I hope these two examples help show you how two similar machines can 
vary drastically in performance with similar hardware. Differences in 
implementation make a BIG difference.

Slainte,
Sherwood McGowan