Can anybody explain why open-source Asterisk is favourable in comparison with a traditional PBX system from a vendor such as NEC/Syntel/Matrix or Siemens.
closed as not constructive by Dave M, Sven♦, Michael Hampton♦, MadHatter, MDMarra Sep 26 '12 at 18:48
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I would separate your question into 2 areas:
Regarding the first one, I believe there is not much dispute, being VoIP extremely more powerful than traditional PBX, but to name a few:
You will find more reasons applying to your enviroment at Wikipedia VoIP
Once you have established you will go VoIP, you have a basically 2 options: propietary or open source implementation/platform. Both share the same VoIP features, but by going open source you also gain:
Asterisk as an open source VoIP platform is very good, been working with it for more than 7 years now, but it has a learning curve. If you want to avoid this, you can go with Asterisk embedded appliances (like Digiums Switchvox) or you can use one of the several asterisk-centred distros like Elastix). There are also several commercial offerings that use Asterisk internally, so you gain the turnkey approach of proprietary offerings without losing your freedom.
You can find more info on the Asterisk project at http://asterisk.org/
Being in a position currently where the powers that be bought a Panasonic PBX.
There's a bunch of features that aren't there (or rather, are individually licensed). Such as MeetMe (conference calling), or hot-desking.
There's also the problem that all the phones are effectively hard-wired to their ports. They had to run new cables for the phones, instead of using our structured cabling. They have to come in every time we want to move a phone, or change a name, and refuse to do a handover and give us the access software and magic runes for the hardware. It's also more expensive. There's vendor lock-in associated with the hardware, and the phone handsets, and the conference phones, whereas with Asterisk, you can use any phone that supports SIP. Oh, and the vendor's phones don't support SIP generally, so once you've got them, switching to Asterisk isn't cost effective.
Choose Asterisk. Or better, Freeswitch. Seriously. You can do things with Asterisk that are impossible/difficult/expensive to do with a traditional PBX. There are even Asterisk appliances (and virtual appliances) available that will give you a plug-and-play experience and a web-based configurator.
In 2012, there is no reason to choose a vendor-specific hardware PBX. Really. No reason at all.