[asterisk-users] Problems with the voice quality under load

Ron Wheeler rwheeler at artifact-software.com
Mon Mar 2 09:56:35 CST 2015

Have you done the math for the network connections? BTF and external
What bit rates for the sound?
What codecs?
How are calls coming in - SIP - analogue

Disks OK(low IO per second)? Caching working OK?

CPU may not be the problem if your CPU utilization is really that low.


On 02/03/2015 10:26 AM, Mordechay Kaganer wrote:
> B.H.
> Hello, all :-)
> We have a cluster of Asterisk (v. 11.9) servers that host IVR 
> applications. The servers work behind SIP proxy (kamailio) for load 
> balancing.
> All servers are in 2 processor configuration, 8-10 cores per CPU.
> When a particular server gets about 500 concurrent calls, the sound 
> quality begins to degrade, the sound plays slowly and with clicks. As 
> far as i understand, it's because asterisk is unable to send the voice 
> stream in time i.e. the server is overloaded.
> What i don't understand is, at the time that the server appears to be 
> overloaded and the audio quality is bad, actual server's load is no 
> more than 30-40% (60-70% idle CPU on average). IMHO, this indicates 
> that for some reason the server is unable to use it's CPU capacity 
> efficiently. May be because of some kind of thread contention inside 
> asterisk?
> I have read blogs that advice to divide physical server into several 
> VMs and they claim that this will improve the total capacity. In my 
> own experience, this did not work very well and seems like the 
> visualization actually made the quality worse.
> Do you have any advice for me (other than purchasing more servers ;-) ?
> Thanks!
> -- 
> משיח NOW!
> Moshiach is coming very soon, prepare yourself!
> יחי אדוננו מורינו ורבינו מלך המשיח לעולם ועד!

Ron Wheeler
Artifact Software Inc
email: rwheeler at artifact-software.com
skype: ronaldmwheeler
phone: 866-970-2435, ext 102

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