Milestone – a full virtual Asterisk phone system

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About four years ago, we switched our office phone system from a proprietary ISDN PBX to Asterisk with Cisco 7940 handsets. It was an instant success and has been running without interruption ever since. It routes incoming faxes to email, provides voicemail, soft-phones and conference rooms, allows us to take our extensions with us wherever we are in the world, provides us with unlimited incoming and outgoing lines over SIP gateways and all the other amazing stuff which Asterisk provides. It was Asterisk which first made me realize that open-source systems can be a whole lot better than closed-source – especially in the proprietary world of telephony.

The only thing which bothered me about our Asterisk PBX was that it was running on a Dell server equipped with a rather obscure Junghanns quad-port ISDN board. It worried me that if either the server or the board died, it would take us quite some time to restore service.

What I really wanted was Asterisk running as a virtual machine, so I could back it up like all our other VMs and move it around within our network infrastructure as needed. Up until now, this wasn’t practical because of high resolution timer issues with the conferencing features. Finally, with the newest Asterisk versions (we’re using the latest beta of version 1.6.2) running on the newest Linux kernels (Debian), its feasible to run it as a VM.

So, as of today, we have our Asterisk PBX virtualized – no moving parts. It connects to our ISDN lines via a Voxtream Parlay voXip gateway. We’re running it on VMWare server 1.0.10 on a dual quad-core Xeon 5420 server with 12GB RAM (the server is running plenty of other VMs alongside the Asterisk VM) . It uses a scarcely noticeable amount of CPU during regular telephony where Asterisk is just connecting SIP end-points. Only conference-rooms, where the Asterisk server is transcoding multiple streams of voip traffic, actually require much CPU resources. Even there, based on our tests, we don’t expect any significant burden on the server.

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