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Open Source Initiatives

What Is Open Source for Communications?

The open source revolution that is taking place throughout the world of software development cannot be denied. However, for those outside the community of users and developers of open source software, misunderstandings arise about exactly what constitutes “open source software”.

The Open Source Initiative defines “open source” as follows:

“Open source is a development method for software that harnesses the power of distributed peer review and transparency of process. The promise of open source is better quality, higher reliability, more flexibility, lower cost, and an end to predatory vendor lock-in.”

Notice that this definition does not mention free (that is zero cost) software, which is often the first thing that many people think when asked about their understanding of open source. While it is true that in an open source project the source code is always made available, it is the open source license itself that dictates the terms that the code is distributed under. The open source license does not prevent you from building a commercial offering around open source software.

Some common open source business models include:

  • Hardware Pull-Through
  • Dual License
  • Paid Add-On Modules
  • Subscription-Based Support
  • Community Edition
  • Licensed Software Modules
  • Consulting

Some of the licenses that you hear most about are:

  • Apache license
  • BSD-style licenses
  • GNU General Public License (GPL)
  • GNU Library (or "Lesser") General Public License (LGPL)
  • MIT license
  • Mozilla Public License (MPL)
  • Eclipse Public License (EPL)

For a complete list and explanation of these licenses, please visit the Open Source Initiative website

Open Source for Communications Market Trends

Within the communications space, open source is making its best inroads in the SMB space, providing IP PBX functionality. According to a 2009 Eastern Management Group Study [“Open Source PBX is 18% of North America Market”, January 2009], “Open source PBXs accounted for 18 percent of the 15.88 million line market for business telephone systems in North America in 2008”.

In terms of percentage of market share, open source PBXs represent the largest single identifiable category provider of PBX systems. Since that report was done we have seen a continued increase in IP PBX deployment, replacing traditional TDM and more recent Hybrid systems.

Open Source VoIP software.

Benefits of Open Source for Communications

As stated in the definition of open source software at the beginning of this paper, the promise of open source is better quality, higher reliability, more flexibility, lower cost, and an end to predatory vendor lock-in.

There is certainly room to argue that open source software will bring better quality and higher reliability to the communications (specifically the telecommunications) market, as this segment has always been the home of systems that are held to the highest quality and reliability standards. Anyone who has spent time in this field knows that most telecommunications systems are expected to run at “five nines” availability. This means that systems are expected to be available 99.999% of the time. This translates into less about five minutes of downtime per year. And some systems are now targeting “six nines”, or about one minute of downtime per year, as an achievable goal.

However, flexibility, lower cost, and no vendor lock-in are certainly benefits to the communications market when using open source. When much of the base functionality of a communications project is considered a commodity when sourced from an open source project, it is the skill and service of the implementation partner that is the sharp focus of that implementation. If a vendor of choice is not delivering on the implementation deliverables, companies can switch to another vendor midstream with little loss of investment because the base software of many open source implementations is the same (and they support the same basic network interface and endpoints).

Because TCO and ROI are closely tied to the vendor that is used when deploying an IP PBX solution, the ability to change vendors (or even bring support and implementation under the existing IT Infrastructure) without adding capital expense to the project enhances the decision to use an open source solution.

As the open source communications market and the solutions it provides mature, we believe these same benefits that are currently being seen by many small businesses, will soon become achievable in the enterprise and carrier space [Asterisk,, August 2010].

Open Source for Communications Technology

Software that has been developed using an open source model can appear nearly anywhere in a systems architecture, from the operating system up through the user interface.

Linux is an example of an open source operating system. It has a large and vibrant community of developers, users, and support organizations that continue to evolve the project.

Other open source projects provide different functionality. Apache is a popular open source web server. MySQL is a true multi-threaded, multi-user, SQL database management system that currently has more than eleven million installations. PHP, Perl, and Python are programming languages that can be used to create dynamic web pages and server-side applications.

These are just a few examples of where open source software can be used in any system.

Within the open source communications space, the leading open source package is Asterisk, with nearly 90% of all open source IP PBX projects being implemented on Asterisk or a derivative or fork of Asterisk.

However, a number of other open source communications projects are now getting significant traction in the space. For example, FreeSWITCH is an open source IP PBX project that has been used as the basis for many IP PBX implementations. Also, projects such as YATE, Kamailio, and OpenSIPS are less task specific than Asterisk, in that YATE is designed to be a general-purpose telephony engine, while Kamailio and OpenSIPS provide proxy/router functionality. Many other open source communications projects exist that provide a variety of other functions.

Service Logic Execution Environments (SLEE) play an important role in the telecommunications network, especially when creating applications that marry the web and mobile experience. Neither SLEE nor OpenSource are required to to create applications that marry the web and mobile experience, but if you are apt to use OpenSource as your development philosophy and are interested in an OpenSource one, Mobicents offers the only OpenSource JAIN SLEE platform. Mobicents was acquired by RedHat in 2007, and is part of the JBOSS Communications Platform, also part of RedHat, so they have a great track record in the OpenSource telecoms world. Essentially, JBOSS is the application server and Mobicents would be the JAIN SLEE stack that “feeds” the application server with the telecommunication protocols.

In addition to the open source software that is at the core of many projects, a group of hardware companies make network interface devices and endpoints that are specifically designed to work with open source software projects.

Dialogic® Blue™ Telephony Boards

The new Dialogic® Blue™ product line is aimed at the needs for the open source market. The Dialogic Blue product line consists of passive and active boards. The Dialogic® Blue™ OneSpan-24/30-S-LP Telephony Board is a passive board. All other boards are equipped with Echo Cancellation Hardware.

The active Dialogic Blue Telephony Boards are available as 4 versions offering from one to eight Span connectivity. Their names are Dialogic® Blue™ OneSpan-24/30-H-HL, Dialogic® Blue™ TwoSpan-48/60-H-HL, Dialogic® Blue™ FourSpan-96/120-H-HL and Dialogic® Blue™ EightSpan-192/240-H-HL Telephony Board. "H" stands for hardware echo cancellation, while "HL" stands for Half Length form-factor.

Dialogic® Media Gateways Series

Dialogic® Media Gateways (DMG Series) allow an IP telephony server, such as Asterisk, to operate in native IP mode while providing PSTN and/or TDM PBX connectivity. Because the connectivity is totally transparent, no load is added to the IP telephony server's operation.

Since the DMG Series manage all the complexities of the PSTN connection, systems can be confidently installed anywhere in the world, whether they are interfacing with analog, T1, or E1 networks. No IP telephony server software changes are necessary. The external appliance gateway handles the PSTN connection, while the server continues to operate in its native IP mode.

Dialogic® Diva® Media Boards

Dialogic® Diva® Media Boards are in worldwide use as part of Asterisk-based PBX systems. In an Asterisk-based solution, the Diva Media Boards offload most media processing tasks from the Asterisk server to the Diva hardware, resulting in more reliable and scalable implementations. The Diva Media Boards are supported via the Chan_capi channel driver.

The Chan_capi channel driver (formerly also called chan_dialogicdiva) allows Diva Media Boards (Analog, T1/E1, and ISDN BRI/PRI) to work transparently under Asterisk as a PSTN interface. The Chan_capi driver gives Asterisk developers easy access to advanced media and signaling functions, which are not available with media boards from other vendors.

  • Enhanced Media Functions — Hardware-based fax, large conferences, echo cancelation (up to 256 ms), FoIP (T.38), DTMF clamping, pitch control, volume control via DTMF, noise suppression, automatic gain control, and others. See a live demo of a running Diva based system at
  • Call Control Enhancements — QSIG extensions supporting all major PBX, ISDN supplemental services (such as explicit call transfer), and call hold and retrieve. Conventional SS7 (ISUP for ANSI and ITU) and SIGTRAN signaling are also supported.

Dialogic® DSI SS7 and SIGTRAN Protocol Stacks

Dialogic® DSI SS7 and SIGTRAN Protocol Stacks are widely used as part of the Mobicents SLEE environment. Signaling is a very important aspect for what Mobicents does and Dialogic provides these necessary capabilities.

Systems with DSI SWS can operate as network interface servers for web-based application server clients. DSI SWS can enable both web services and traditional services because it includes both web server software for HTTP transport and TCP/IP protocol software for connection to application servers.

HTTP and XML open standard conventions enable the use of DSI SWS with service creation environments such as Oracle WebLogic, IBM WebSphere, JBoss, GlassFish, and others.

Dialogic® Products and Open Source Projects

Dialogic® Diva® Media Boards for Asterisk
Dialogic® Diva® Media Boards can be used directly within an open source Asterisk PBX to provide a native connection to the PSTN network. Diva Media Boards have onboard DSPs that deliver the media and signaling needed for high-density communications processing.

Dialogic® Media Gateways
Dialogic® Media Gateways allow an IP  telephony server, such as Asterisk, to operate in IP mode while providing transparent PSTN connectivity without additional load on the server.