Asterisk preps assault on unified communications

Having taken on the IP PBX vendors with its free Asterisk software, Digium is now setting its sights on providers of business-grade unified communications platforms like Avaya, Cisco, Microsoft and Siemens.

Burning questions about Asterisk open source PBX platform

Digium this week announced Asterisk Scalable Communications Framework, its new software project to support massively scalable and fault-tolerant communications networks that customers can integrate with their own applications more readily than they could with commercial UC platforms.

While still under development, SCF and its high-availability potential were demonstrated this week at Astricon, the Asterisk user conference. The company showed how an SCF phone call could survive the failure of its call-setup server and later transfer the same call. A developers’ release of SCF is available at

SCF is highly modular with open interfaces into the modules and into the communications channels between the modules, says Kevin Fleming, director of software technologies for Digium. That design is meant to make SCF and its components open to software developers that want to integrate communications functions into their own applications, he says.

So if a company wants communications functions to be part of its CRM or ordering application, these interfaces will enable making them natively part of the applications, Fleming says. “We’re hearing that people who build these applications want to interface with all aspects of the communication platform and control it,” he says.

It will be another year or more before SCF is able to support a limited number of features in production networks, he says, but Digium is announcing it now in order to attract developers interested in influencing the shape of the final product. The architecture as set down by an oversight committee will support all known forms of communication – voice, video, instant messaging, SMS, e-mail, presence – and is flexible enough to embrace others as they come along, Fleming says.

Key to the architecture are the open interfaces that enable applications to be treated as peers of components of SCF, regardless of what language the applications are written in. SCF itself is written in C++, but the interfaces support virtually any popular programming language such as C#, Java and Python, he says.

At this stage, Digium is hoping to attract developers who will actually help write SCF code, but also people who understand what types of applications businesses will want to integrate with SCF. “We’re looking for some blue-sky brainstorming,” Fleming says.

Asterisk started out as the homegrown telephony platform for a startup, then became open source and then the basis of commercial software supported by Digium. The product wasn’t designed from the outset as a commercially scalable product.

Just as commercial VoIP vendors have revamped their IP PBXs to become UC platforms, Digium is starting on its own UC project with a clean slate rather than trying to graft UC onto Asterisk, says Fleming. SCF is intended for large enterprises or even service providers, he says.

In addition to being modular, SCF can be distributed across multiple machines and locations. So pieces of it might be in a data center, but redundant modules might be located in branch offices to ensure that services survive if the data center fails.

Fleming says Digium has been developing SCF code since April and that it will be at least a year before it is ready for real world use.

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