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Digium and Open Source Software

Should you consider Asterisk or any of the other open source communications software packages? Our columnist helps you get familiar with the pros and cons, the ins and outs of open source.

I confess I've not been nearly as knowledgeable as I should when it comes to IP telephony/UC open source software (at least I admit it).

Normally, I'd focus more on the "traditional players" but given this knowledge gap and wanting to do something different, I thought I'd take a page from Seinfeld's George Costanza and do the opposite of what I'd normally do (see "Opposite George).

With that, I'd like to thank Mark Amick, Digium's Director of Product Management for all of his assistance with my research for this article and invite you to take a look at the company Digium and their open source software product, Asterisk (

Open Source Software (OSS)
As mentioned in my last column, open source software (OSS) is computer software where the source code is made available at no cost with the right to modify the code and make it available to anyone as long as certain term and conditions under which the software is distributed are followed.

Keep in mind that for the OSS community, the concept of "free software" refers to the freedom to run, distribute, change, study, and improve software; not the license cost. In other words, OSS is more like "free speech," rather than "free samples" at Costco. For more on OSS rules/guidelines see and

Asterisk the Software, Digium the Company
Asterisk is the open source telephony software created by Mark Spencer in the late 90s as an alternative to more expensive proprietary PBX systems. At the time, Spencer needed a telephone system to distribute customer service calls to his Linux engineers and decided to "build" his own PBX rather than pay for a new system.

Spencer also opted to make Asterisk available as open source software to minimize ongoing development costs (this business model was also consistent with the anti-proprietary software movement of the time). A beautiful example of necessity (+ limited capital funds) being the mother of invention.

Founded in 1999, the company Digium owns/manages the Asterisk intellectual property. What this means is that if a software developer wants to create and sell a new product based on Asterisk code and not make the new product available for free public use, the developer would have to buy a commercial license from Digium for the rights to sell the new "proprietary" product. Because Digium owns the Asterisk intellectual property, it also has the right to value-add and re-package the software for commercial sale.

Note that when I talk about Asterisk I’m referring to it as IP PBX system software, but know that Asterisk can also be an open source voice mail, VoIP gateway, IVR, audio conference bridge, or basic ACD/call center application. For these other apps, see this webpage.

Open Source Software and the IP Telephony Market
I won't spend too much time here, but know that Digium's Asterisk is the most widely used OSS telephony product in the world. Asterisk dominates this market with >85% share.

Typically deployed by SMB customers (I know I'm breaking my SMB rule), Digium holds a 2.5% market share in the North America market, which is comparable to proprietary manufacturers such as Siemens and ShoreTel. Not bad company for an open source product. For more information on Digium and market share, see:

* Allan Sulkin's No Jitter article "2009 Enterprise Communications Market Results: Cisco Retains Leadership Status in a Down Market"

* John Malone's No Jitter article "Open Source PBX is 18% of North America Market"

* Gartner's Corporate Telephony MQ 2009 analysis

Digium's Business Model
If Asterisk is free, open source software, how the heck does Digium make money? Actually, they make money in several ways.

1. Interface cards. Customers still need hardware interfaces for phones and analog devices, central office trunks, and T1/E1 circuits. For example, list price for a T1 card is $730, and a 4-port analog card is $573.80.

2. Training. While Asterisk downloads are free, customers still need training to design, implement, and support the product. If you want to be a "Digium Certified Asterisk Professional" (dCAP), you need their certified training. Training costs vary but to give you an idea, Asterisk FastStart training (an intro class) is $1,995, while the Asterisk Advance course for dCAP certification prep is $3,000. The dCAP exam costs $300.

3. Support Services. Developers and customers often want a "safety net" if they get stuck or in trouble. In this case, they can look for help from the Asterisk user community or Digium direct.

If you want Digium support that includes bug fixes + technical support, you pay an annual flat fee based on the number of Asterisk servers deployed. Fees can range from as little as $595/yr for one server with 12x5 support and up to $7,995/yr for up to 10 servers with 24x7 coverage. Discounts apply for multi-year contracts. Digium support is available for any Asterisk application (IP PBX, voice mail, ACD, or IVR system). For support subscription service offers and pricing, see this website.

4. Commercial software licensing from software developers who "create" their own proprietary products using Asterisk.

5. Value-added Asterisk products such as AsteriskNOW and Switchvox.

6. OEM licensing for their Asterisk Business Edition (ABE) system

Interestingly, Digium does NOT sell/distribute SIP phones. Customers can source these endpoints through their partner companies such as Polycom, Aastra, or Grandstream.

Asterisk interface cards, support, or value-added products are sold directly by Digium or through their distributors/authorized resellers. To minimize channel conflict, partners can offer discounts below Digium's direct prices. So if you want product or support direct from Digium, you'll pay a premium for it. Digium will support hardware regardless of where it was purchased.

Digium's Asterisk IP Telephony Products
Digium's IP telephony product portfolio is made up of the following options:

Asterisk: This is the core open source telephony software. You download it, you build it. Again, developed in 1999, the product has been enhanced by the (devoted) Asterisk developer community for the past decade. Overall industry consensus is that the product is solid, stable, and ready for "primetime."

Counter-intuitive (for me), larger deployments typically are based on Asterisk because these customers want the flexibility to build the system any way they want, not how the vendor packages it. This design flexibility is what appeals to the enterprise customers using Asterisk.

For a summary of features available with Asterisk, follow this link.

While the software is free, remember that Digium's business model is based on deriving revenue from hardware (cards), training, and support subscriptions. The differences between subscription services vary from SMB Level 1 for only 1 server with 12-12 business day coverage to Enterprise Level 4 with 24x7 support for 10 servers or more. Here’s a high-level sample of the subscription service costs:

A complete summary of the Digium direct subscription services is available here.

If you need more advanced functionality like speech recognition, IVR prompts, text-to-speech, a GUI for system administration, or even a Skype interface, there is an additional license cost. For example:

If you don't want to "build your own" IP system, you have another option:

AsteriskNOW: AsteriskNOW is free software that is "bundled" with additional Digium installation and configuration services. The product is targeted at smaller customers who want a "free" PBX but additional support. It also comes with a GUI for enhanced system administration.

As with basic Asterisk software, 3rd party apps like those cited in the table above are licensed as needed. For a comparison between Asterisk and AsteriskNOW, see the PDF datasheet entitled "Asterisk Software Comparison."

Asterisk Business Edition (ABE): ABE was the commercialized version of Asterisk bundled with advanced installation and support services. However, since I started working on this column, Digium has decided to stop offering it as a "retail" product and will license it for OEM customers only. Any customers who have ABE currently installed will continue to be supported by Digium.

Switchvox: Acquired by Digium in 2007, Switchvox is an IPT/UC software only product designed for up to 400 users. Built on top of the Asterisk telephony engine, it's not open source or free(except for the Home version). Switchvox can be installed on customer server hardware or pre-installed ("turnkey") by Digium on their servers.

Switchvox comes in three versions: Home, SOHO, and SMB. The Home version of Switchvox is free and comes with no Digium support. Home is targeted at the very small SOHO (5 or 6 people) that need an inexpensive voice system. As the comparison table linked below shows, it is feature-limited as well as limited to a maximum number of 8 users.

SOHO is sold as software only or on an Asterisk appliance. SOHO is designed to support up to 20 users. SMB is also available as software only or on three Asterisk appliances. The software is identical for all three models; the only difference is capacity. SMB is designed to support up to 400 users.

For a comparison of Home, SOHO and SMB versions, see this link.

For SOHO and SMB, software licensing is based on subscription pricing with an "activation" fee in year 1 and annual user license renewals for support plus software upgrades.

For example, SMB model AA305 (the middle option) has the following software licensing:

Software updates and maintenance are a separate annual recurring cost of $550 per server. Support and software updates are provided in Year 1. User subscriptions must be purchased in Year 2+ for customers to have access to Digium support and software updates/patches.

More Switchvox model pricing can be found here.

Bottom line on Switchvox: if you're not a technical customer, don’t have time to invest in "building" your own voice application platform, and need other UC applications such as mobility, consider Switchvox. Also note, the Switchvox product is the primary focus of the indirect channel.

Wrap up
Companies considering Digium need to do their homework and decide if they really want to develop their own voice platform. If you do, know that you'll need resources (time and people) + fairly deep skill sets that include Linux administration, TCP/IP networking, VoIP/TDM telephony, and script programming to implement an open source solution.

You'll also need to understand what is needed for:

* All functionality/applications that may require optional licensing costs or special integration.

* The right support/subscription model.

* All hardware components (gateways, interface cards, SIP devices)

* All labor and professional services

* Your company's time and resource requirements (implementation and post-implementation)

While the solution is likely to cost less than proprietary systems, you may be surprised to discover that an open source software solution does not mean "free" (as in cost or time investment). That said, the above advice also certainly applies to any company looking at buying new technology.

Lastly, the "wild card" for me is Digium's service and support capabilities either direct or indirect (this area is also a question mark with many vendors). If you're a Digium customer, I'd love to hear from you on the pros/cons of your experience with Digium's implementation or post-implementation support.

For more background on Digium and the Asterisk Project, here are few links for reference:
"Get Started Video"

I hope you found this look at Digium helpful. Here's what's ahead for the upcoming columns in July and August:

* Siemens OpenScape Voice
* IBM Sametime 8.5 (Brent Kelly senior analyst and partner at Wainhouse Research joins me for this article)
* Alcatel-Lucent
* Avaya

Until next time, all the best.