Asterisk and IP Telephony

If you aren't already aware of Asterisk, the open source PBX, then where have you been?

Asterisk is an interesting beast and it builds on and enhances a number of the hottest current technologies:

1. Asterisk is an exchange that integrates with IP Telephony. More and more companies are combining their internal telephone and IT networks tusing IP Telephony.
2. Asterisk provides connectivity to VoIP services. Skype may get more press, but there are plenty of other IP services out there and Asterisk can merge your plain old telephone (POTS), E1/T1, ISDN and VoIP services together so they are accessible through a single phone system. Now when you dial, Asterisk can choose the cheapest and most effective solution automatically. For incoming calls, regardless of source, they can ring on your one phone.
3. Through WiFi technology, Asterisk (with VoIP and IP phones) provides cordless and wireless phone technology

Asterisk marries all of this with other useful exchange based services, like Voicemail, Voicemail to Email gateways, call routing, and all those other features we take for granted on our phone system.

This week we've had an announcement of Bonjour (formerly Rendezvous) support, and a survey which shows that IP PBX like Asterisk are increasing.

Where I see a real explosion in use of Asterisk is in the SME market, particularly multi-location organizations.

To give you an example, one of my clients has three main offices, one each in England, Scotland and Wales, and then has a number of staff that frequently work from home or on the road. We’re still talking fairly small; the entire company has less than 15 full time employees. They already use email through local DSL connections (through a solution I host, to make connectivity easier), but have their own telephone systems in each office, not connected other than through the PSTN. There are currently no dedicated servers at any location, although they have an idle Windows XP box that acts as a basic file server.

Obviously a lot of time is spent communicating information between offices, the bulk between the two main offices in England and Scotland, so they approached a typical communications company to talk about how to improve the current system with inter-office communication, voicemail and other ‘modern’ features they don’t currently have access to. They recommended a permanent link between the two offices – at a base cost of over £8000 per year – plus new servers, exchanges and equipment to support it.

This service would have done nothing more than provide a 128Kbit link for the purposes of email and voice calls, including the ability to transfer calls between offices.

Now email is already handled through the public DSL links they have to the Internet, and direct links would require a server at each end (and therefore management of said servers) to keep things running. Calls between offices are frequent. Transferring a call (for example someone ringing the Scotland office, but wanting someone in the England office) are rare and happen less than five times a week.

All in all the cost outlay would far exceed the actual cost of calls in the current situation and only really offer the slightly dubious functionality of transferring calls between offices.

Asterisk could certainly resolve the functionality needed in each office – the basics of a PBX plus Voicemail and other items are key to Asterisks abilities. The cost of a server, interface hardware and the setup is not insignificant, but nowhere near the costs quoted by the ‘communications experts’.

Even better, because Asterisk also supports VoIP we can ‘connect’ two Asterisk servers together over a network, including the Internet. So, if Fred in England wants to call Barney in Scotland it effectively costs nothing for the call when using their existing DSL links.

Better still, with VoIP those users working at home or on the road need only get an Internet connection and then have full access to their voicemail and telephone service, even having a dedicated phone number to their desk, car or hotel that remains constant wherever they go. This is functionality that would be well nigh impossible, and quite probably prohibitively expensive, if handled through ‘traditional’ communication means.

Given the choice – expensive, inflexible and with an increased management overhead, or with a comparatively plug-and-play, and cheap solution like Asterisk, I know which I would choose.