The document compares two popular open-source VoIP technologies, Asterisk and FreeSWITCH, detailing their differences in functionality, performance, and usage. Asterisk, created in 1999, is user-friendly and suitable for basic PBX needs, while FreeSWITCH, developed in response to Asterisk's limitations, offers advanced capabilities and better handling of concurrent calls. The choice between the two will depend on specific business needs, with Asterisk showing ease of use and FreeSWITCH offering greater modularity and scalability.

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Asterisk vs. FreeSWITCH: How Are
They Different?
The two most popular open-source VoIP communication technology platforms in the
VoIP domain are Asterisk and FreeSWITCH. Not only are they open-source
technologies, but both are also powerful enough for developers to develop any

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complex communication and team collaboration VoIP solutions. Both hold a king’s
share of the VoIP application market share, but each technology holds an advantage
over the others, even though both platforms share many commonalities. By choosing
one over the other technology, businesses enjoy certain benefits. In this article, we
will have a quick brief on each of these VoIP solution development platforms to
understand what makes them different.
Introduction to Asterisk and FreeSWITCH
What is Asterisk?
Mark Spencer developed Asterisk in 1999 as a software program that distributes
calls just like an expensive PBX. His small team developed the Asterisk software for
call handling and distribution for their company, Linux Support Systems, which was
later rebranded as Digium. Being an open-source technology, the Asterisk program
was adapted to be the base for many open-source, proprietary, and hybrid PBX
systems, such as FreePBX, Elastix, and PBX in a Flash. Over the course of time,
Asterisk has evolved to be an open-source PBX in its own right and can be used as
a standalone system.
What is FreeSWITCH?
Limitations and shortcomings of the Asterisk platform resulted in the conception of
FreeSWITCH in 2006. A reputable Asterisk developer, Anthony Minessale, decided
to fix some of the perceived issues of the Asterisk platform and built a program from
the ground up. It eventually became known as FreeSWITCH by 2007. FusionPBX is
predominantly using FreeSWITCH solution as its switching core.
If you are wondering why to switch from traditional to VoIP calling, here is an article
on “PSTN v/s VoIP”
Internal Workings of Each Technology
Dialplan is the core of any Asterisk system. It is a scripting language with the
modules placed in the configuration directory instructing the Asterisk system on what
to do. Developers can achieve different functionalities, such as receiving calls on a
specific SIP channel, connecting calls to IVR, or routing calls using dial plans in
Asterisk development. The configuration files for Asterisk are saved as normal text
files.
FreeSWITCH uses a different approach; the system is developed in C, and the
fundamental program basis is more structured. In contrast to the Asterisk design,
where each channel has its thread and memory space, FreeSWITCH processes

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threads that execute consistently throughout memory.
This is also one of the reasons why FreeSWITCH requires more RAM than Asterisk.
In addition, the configuration files for FreeSWITCH are saved as XML files which
may be difficult to alter but highly beneficial for automating certain processes.
FreeSWITCH features a well-defined API, where the different functionalities are
turned into modules. Developers, offering FreeSWITCH development services,
can cherry-pick the needed modules and integrate them into the FreeSWITCH
system based on the needed modules. Asterisk’s open and fragmented design
means dependencies on parent modules for certain functionalities. So while the
developers can experiment with unique features, they are also more prone to
encounter errors, functionality breaks, and bugs.
Basic Functionality
Both technologies provide most of the same features on the most basic level. Any
FreeSWITCH or Asterisk-based switch on the market should provide voicemail, call
recording, and IVR menus. The process of creating extensions and gateways is very
similar for either architecture. However, the number of users supported would vary
based on RAM and the core performance of the server.
In addition to connecting between different endpoints, including mobile networks,
VoIP systems, and the Public Switched Telephone Network (PSTN), both
architectures have specialized interfaces for connecting to other servers of the same
platform (i.e., Asterisk connecting to other Asterisk servers or FreeSWITCH to other
FreeSWITCH servers) Asterisk uses a dedicated interface for connecting to other
Asterisk systems using the IAX protocol (Inter-Asterisk eXchange). Thankfully,
FreeSWITCH doesn’t require specialized protocols to communicate with other
servers.
Advanced Functions
MultiTenancy
FreeSWITCH characteristics include the ability to provide multi-tenancy capabilities.
This means multiple user branches can use a single FreeSWITCH system under
individual domains or subdomains as exclusive entities. Unfortunately, to support
multi-tenancy in an Asterisk system would require a proprietary system developed on
top of the Asterisk platform. This is an expensive affair, and a major reason
companies avoid multi-tenant Asterisk VoIP solutions.

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Clustering
Installing all roles from a single PBX server is like putting all your eggs in a single
basket. Therefore, for large-scale or enterprise-level PBX servers, it is suggested to
split each system, fulfilling a certain function, into a different server, i.e., distributed
architecture.
Asterisk is primarily designed to run on a single system. However, for deployments
that require multiple Asterisk servers, distributed device state support allows an
Asterisk server to coordinate with multiple Asterisk servers effortlessly. However,
Asterisk is still a single system platform at the core level, and certain features may
feel set in stone during Asterisk software development.
On the other hand, FreeSWITCH offers strong interconnection capabilities, allowing
individual systems in the cluster to perform numerous functions.
IM capabilities
Asterisk and FreeSWITCH systems support advanced communication functions,
including chat (instant messaging), video calling, and conferencing. However, most
Asterisk solutions rely on an add-on (OpenFire) for IM capabilities, for which
companies must shell out additional payments. For IM capabilities in FreeSWITCH,
the XMPP service must be activated, and the end devices must be properly
configured.
Device Deployment Capabilities
Device deployment on either FreeSWITCH or Asterisk networks varies considerably.
Asterisk supports many endpoint management modules for IP phones and
softphones, but they cost around $100 for access to the provisioning software.
FreeSWITCH systems take a hit here as although it includes various configuration
files integrated into the platform for provisioning phones; the choice is severely
limited compared to Asterisk. However, FreeSWITCH has an edge as it supports
auto-provisioning.
Documentation
Being a slightly matured environment, most SIP providers have comprehensive
documentation for connecting systems to any Asterisk gateways. FreeSWITCH
offers sample gateway configuration templates, but it’s better to call your SIP
providers for troubleshooting when facing any troubles in connecting a FreeSWITCH
gateway.

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Minimum Server Hardware Requirements
Asterisk v/s FreeSWITCH – VoIP Platforms
Comparison
Performance: While FreeSWITCH requires more RAM and processing
capabilities than Asterisk, it can also handle four to ten times the concurrent call
volume. Sofia-SIP stack inclusion ensures communications control is now
implemented in a trustworthy, well-tested manner for FreeSWITCH.
Stability: Since Asterisk is generally a single system arrangement, it relies on
shared resources for performing different tasks. While this works smoothly in a
restrictive environment, sporadic deadlocking, race conditions, and possible data
corruption are the most common scenarios in large-capacity situations. However,
since FreeSWITCH processes threads that execute consistently throughout memory,
the system remains stable in large capability situations. Moreover, the overall
stability of distributing the functionalities using APIs ensures FreeSWITCH servers
have minimal downtime.
Versatility: Asterisk and FreeSWITCH offer flexibility in adding new features and
applications. However, FreeSWITCH has the edge over Asterisk. FreeSWITCH
supports a wide range of programming languages and platforms, including C/C++,
Python, Perl, Lua, JavaScript, and.NET. So, incorporating the FreeSWITCH core
library in other programs is relatively simpler.
Applicable Usage: Asterisk is better adapted to suffice the PBX requirements
of any organization. FreeSWITCH has a lot better choices to offer in this situation.

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It is a platform with capabilities to provide better call management and billing
features on top of just basic VoIP calling.
Configuration/Design: Setting up and managing administrative tasks on
Asterisk is easier as it uses plain text files for configuration and dial plan design. At
the same time, FreeSWITCH configuration uses XML, which makes manual
configuration file maintenance a slightly difficult affair but makes automation easy.
Moreover, dialplan creation at a higher level is possible in FreeSWITCH, all thanks to
the improved regular expression support and increased number of matchable call
attributes. An expanding FreeSWITCH developer community means FreeSWITCH is
a thriving platform where new features are periodically developed.
Wrapping Up
A properly configured system running Asterisk or FreeSWITCH would make no
visible difference for the end user. From a development aspect, Asterisk is
considerably easier to work with on several levels. On the other hand, ls.
FreeSWITCH offers a better range of modularity and wins when choosing a high-end
PBX that can handle a large volume of concurrent calls. Vindaloo Softtech is a
seasoned VoIP development company with expertise in creating Asterisk and
FreeSWITCH-based business communication solutions for 6+ years.
Author Bio
Sandip Patel – BDE
Author works as BDE at Vindaloo Softtech since 2016. Sandip has 10+years of work
experience in VoIP Software Development Industry. Vindaloo Softtech is software
development and solutions provider that offers FreeSWITCH, Kamailio, OpenSIP,
WebRTC and Asterisk Development.