Skip to end of metadata
Go to start of metadata

1. Concepts and Goals

1.1. How is Asterisk SCF changing the future of communications?

Asterisk changed communications by making telephony affordable for small and mid-sized businesses. Asterisk SCF will democratize communications for organizations of all sizes, from a home user, to the largest enterprise or provider.

1.2. How is this different from Asterisk?

Asterisk SCF is best explained as a product that can be used as a companion for Asterisk to address certain things that Asterisk itself does not address very well. The notable areas that Asterisk SCF addresses are in the fields of scalability, fault-tolerance and high-availability, extensibility and performance. While Asterisk is a multi-function application for voice communications that’s most commonly deployed as a PBX, Asterisk SCF is a framework for building voice, video and text-based communications applications. Asterisk SCF is in heavy development and is not expected to be beta-level software until some time in 2011; meanwhile, Asterisk has over 10 years of development under the hood and currently employs more than 120 helper applications and resources to provide users with configurable solutions.

1.3. What types of users or customers are impacted by Asterisk SCF?

The announcement of Asterisk SCF targets developers. End users and customers are not immediately impacted by the announcement of Asterisk SCF. As developers build applications on top of Asterisk SCF, end users and customers will see impact as they are provided with feature-rich solutions built on the world’s most powerful communications platform, Asterisk SCF.

1.4. Why did Digium decide to initiate the Asterisk SCF project?

Digium began the Asterisk SCF project because of the demands of Asterisk users, who were attempting to solve many problems, focused on scalability, fault-tolerance and high-availability, extensibility and performance, that were difficult to solve with Asterisk. Digium communicated its ideas with a team of respected Asterisk community members and the joint decision was made to develop a parallel project, along side Asterisk, that could address those problems

1.5. Is Asterisk SCF really just Asterisk 2.0?

No. Asterisk SCF is not Asterisk 2.0. Asterisk is a platform comprised of a suite of pre-built applications and tools that allow users to build complex telephony applications. Asterisk SCF is a framework for building real-time communications applications focused at scalability, high-availability and fault-tolerance, extensibility, and performance. Asterisk SCF complements Asterisk by providing developers a simpler path to building large-scale, high-performance, fault-tolerant solutions for voice, video and data communications. Asterisk maintains a suite of applications for terminating with all kinds of telephone calls and protocols. Think of Asterisk as the feature server for Asterisk SCF.

1.6. Is this the end of Asterisk?

No. The release of Asterisk SCF will not impact the development of Asterisk. Digium and the Asterisk community have just completed the 1.8 release of Asterisk, which provides numerous enhancements including SRTP and IPv6 support for SIP; Connected Party Identification Support; Calendaring integration for CalDAV, iCal, Exchange and EWS calendars; a rewritten call logging system; distributed device state; CCSS, CCBS and CCNR support; Advice of Charge, including AOC-S, AOC-D and AOC-E support; and more. Further, the development of the next major release of Asterisk, 10, estimated for release in October of 2011, has already begun. For more information about the Asterisk roadmap, visit the Asterisk wiki at

1.7. What kinds of users will take advantage of Asterisk SCF?

At first, only developers will be able to take advantage of Asterisk SCF. Asterisk SCF is not a user application in the sense that Asterisk is. Asterisk SCF does not provide a suite of user-ready applications that are controlled via configuration files.

2. Business Impact

2.1. What impact does this have on unified communications?

Unlike other communications applications that were designed before the advent of unified communications, Asterisk SCF has been designed from the outset to support an array of communications types, including voice, video, and text. Asterisk SCF is the most-flexible framework for developing unified communications applications available today.

2.2. What impact does this have on the carrier market?

Asterisk SCF provides a framework from which carrier-grade communications applications can be built.

2.3. How does this impact Asterisk licensees?

Licensees of the Asterisk code base are not entitled to licenses of the Asterisk SCF code base. Customers seeking to license the Asterisk SCF code base should contact Digium’s Business Development group. Due to the heavy development which Asterisk SCF is currently undergoing, Digium is not able to present an immutable API to licensees until the 1.0 general availability release of Asterisk SCF.

2.4. Is Switchvox built on top of Asterisk SCF?

No. Switchvox is a collection of many applications, Asterisk as one of them, put together in a complete and turnkey offering to provide small and medium-sized businesses with the best Unified Communications solution on the market.

2.5. Do Asterisk subscriptions also include support for Asterisk SCF?

No. Digium’s open source subscriptions offered for Asterisk may not be applied to Asterisk SCF environments.

2.6. When will Digium offer commercial support for Asterisk SCF?

Commercial support for Asterisk SCF will be offered for Asterisk SCF when it reaches 1.0 General Availability.

2.7. What kinds of commercial support will Digium offer for Asterisk SCF?

Digium has not yet determined the support offerings that it will make available for Asterisk SCF. As the 1.0 release of Asterisk SCF draws near, Digium will announce its support plans.

2.8. Does Digium offer training for Asterisk SCF?

No. While Asterisk SCF remains in heavy development, Digium does not offer training classes related to Asterisk SCF. As Asterisk SCF approaches general release, Digium will announce further details about training programs, classes and materials.

2.9. Is there a migration plan for applications built on Asterisk?

Because Asterisk SCF is not Asterisk 2.0, there is no direct migration between the two. Communication between the two is currently possible via SIP.

3. Project Plan

3.1. When will Asterisk SCF become Beta and/or General Release software?

It is Digium’s expectation that Asterisk SCF will be available in beta with a limited set of functionality in Summer 2011. Transition from beta to release will consume approximately six months, with the explicit note that these timelines are subject to change without notice at any time.

3.2. What should people expect in terms of commercial products and how quickly will they arrive?

Because Asterisk SCF will remain in heavy development for the next 12-18 months, Digium does not expect commercial offerings to appear until such time as Asterisk SCF reaches 1.0 release and general availability. Digium itself will not offer commercial support on Asterisk SCF until the 1.0 release; thus, Digium does not expect to offer commercial products until it is capable of offering commercial support for Asterisk SCF itself.

3.3. When will Asterisk SCF be suitable for development of integrated applications?

Asterisk SCF is suitable for companies to begin experimentation now; however, please note that API changes will continue to be made for as much as the next 12 months.

3.4. When can I start developing on Asterisk SCF?

Today. Visit the Asterisk SCF wiki at to find information on downloading and building the Asterisk SCF source, documentation on the architecture, and see the Roadmap.

3.5. Where can I find the roadmap for Asterisk SCF development?

The roadmap for Asterisk SCF development can be found on the Asterisk SCF wiki at:

3.6. Is there a boundary for the types of applications that will be accepted into the Asterisk SCF codebase?

Currently, no boundary has been set for the types of applications that would or will be accepted into the mainline Asterisk SCF codebase. Digium encourages the community to get involved and participate in discussion about this topic.

4. Technology and Architecture

4.1. Is Asterisk SCF backwards compatible with Asterisk?

No. Asterisk SCF is not a replacement for Asterisk and is therefore not designed to be backwards compatible with Asterisk configuration files or applications; however, calls placed through Asterisk SCF can be connected to Asterisk using the SIP protocol.

4.2. What are the key technical advantages of Asterisk SCF?

Asterisk SCF is focused on solving technical challenges in four key areas: scalability, high-availability and fault-tolerance, extensibility through flexible APIs, and performance.

4.3. How does Asterisk SCF differ technically from Asterisk?

Asterisk SCF differs from Asterisk in a number of different technical ways. Three of the most notable ways are in the component-based architecture of Asterisk SCF, versus the monolithic architecture of Asterisk; the primary programming language used, Asterisk SCF is written in C++ while Asterisk is written in C; and the target platforms, Asterisk SCF is targeted to run on a wide range of platforms including Linux, Windows, Mac OS X, Solaris and FreeBSD.

4.4. Does Asterisk SCF support Digium telephony cards?

Digium telephony cards are supported indirectly by connecting Asterisk SCF to Asterisk, which hosts the Digium telephony cards, over SIP.

4.5. Does Asterisk SCF support Asterisk add-ons like G.729?

No. Asterisk SCF does not currently support any Asterisk add-on products, like Digium’s G.729 offering for Asterisk.

4.6. When Asterisk SCF reaches a 1.0-release state, what will it be, and how will you interact with it?

When Asterisk SCF is 1.0 software, it will be a complete framework for building next generation communication applications. Asterisk SCF will be addressable via many programming language bindings over published APIs.

4.7. On what platforms will Asterisk SCF run as a native application?

The platform support for Asterisk SCF has been divided into two tiers: First Tier, fully supported, and Second Tier, support attempted. First Tier platforms are Linux, Windows, Solaris and Mac OS X. Second Tier platforms are, currently, FreeBSD. For more information, see the Platform Support on the wiki:

4.8. In what language is Asterisk SCF programmed?

The core of Asterisk SCF is programmed in the C++ language. Its components may be programmed in other languages. Example versions of the Routing Service were written in Java and C# for demonstration purposes.

4.9. What languages can I use to build Asterisk SCF components or applications?

Although the core of Asterisk SCF is written in C++, components and applications for Asterisk SCF may be written in C++, Java, .NET, PHP, Python, or Ruby.

4.10. What’s difference between “basic” and “advanced” call routing as mentioned in the Asterisk SCF roadmap?

As used in the Asterisk SCF roadmap, Basic call routing is not scriptable call routing, it’s coded. Advanced call routing will be fully scriptable.

4.11. Is the Asterisk SCF code repository maintained in Subversion (SVN) as the Asterisk codebase is maintained?

No. The Asterisk SCF codebase is maintained in a distributed revision control system called Git. For more information about Git, please visit For more information about pulling Asterisk SCF code from the Git repository, please visit the Asterisk SCF wiki at

5. Licensing

5.1. Where can I find information about licensing of Asterisk SCF?

Please refer to the dedicated Licensing FAQ.

6. Community

6.1. What role does the community play in Asterisk SCF?

The community plays a similar role in the development of Asterisk SCF as its role in Asterisk. One differing factor in involvement of the community between Asterisk and Asterisk SCF has been the community’s involvement from the beginning of Asterisk SCF, prior to code having been written.

6.2. What things does Digium need the community’s help to develop?

While Asterisk SCF is available as Alpha software, Digium needs the help of the community to contribute to the development of the core software. Once Asterisk SCF is available as Beta software, Asterisk SCF will be useful for developers who want to build their own communications applications that can take advantage of the Asterisk SCF framework. For more information, please visit the Asterisk SCF wiki at

6.3. Does Digium’s Asterisk SCF development team include any members who have also worked on Asterisk?

Yes. The development team assigned to the Asterisk SCF project includes both new hires as well as some developers who have also worked on the Asterisk project. The team maintains a brilliant mix of expertise in the areas of Asterisk, telephony, distributed applications, and object-oriented software architecture, design, and development.

7. Miscellaneous Questions

7.1. Is there a central location for Asterisk SCF documentation and project information?

The Asterisk SCF documentation is available at

  • No labels