FreeSWITCH  vs Asterisk

FreeSWITCH vs Asterisk


Asterisk was founded in 1999 as a result of the efforts of a computer engineer named Mark Spencer. His tiny team created the Asterisk software switch for Linux Support Systems, which was ultimately renamed Digium. The Asterisk switch has now been included into a number of PBX systems, including FreePBX, Elastix, and PBX in a Flash. It’s worth noting that Asterisk is an open source PBX in and of itself, capable of functioning as a stand-alone phone system.


FreeSWITCH arose when Anthony Minessale, a well-known Asterisk developer, attempted to address some of the platform’s perceived flaws. As a result, what became known as FreeSWITCH was built from the ground up. The project was first mentioned in 2006, and it was finally launched in 2007. FreeSWITCH is a true open source software switch, and sipXcom (which started as sipXecs) and FusionPBX are the two most popular platforms that use it as their switching core.

Asterisk is designed to be extremely modular at its core, which is evident when viewing the product’s final installation. This is also suggestive of the system’s fundamental composition. During run-time, Asterisk makes use of shared resources, such as software threads, which might cause problems when there are a lot of calls.

FreeSWITCH vs Asterisk

Fundamentals of Switch Design

Despite some complex code built in a variety of programming languages, Asterisk is a remarkably efficient system, as seen by the multiple adaptations available on the internet. 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 own thread and memory space, process threads execute consistently throughout memory. This is also probably one of the reasons why FreeSWITCH often requires more RAM than Asterisk.

FreeSWITCH features a well-defined API that is divided into levels, each with its own function. Asterisk, on the other hand, is slightly more fragmented due to its modular design (though FreeSWITCH also uses a modular paradigm) and does not provide read/write thread locking. Unlike Asterisk, where the more open design allows for more experimentation but also increases the danger of errors and problems, this design secures the FreeSWITCH API.

For configuration, Asterisk uses ordinary text files, but FreeSWITCH uses XML files. Though XML is more difficult to alter, the benefits come in the form of automation, which is extremely useful for bringing together various processes.

Requirements for Hardware and Software

Hardware requirements are difficult to define exactly because each system (i.e., each PBX that uses the underlying switch) has different goals in mind, resulting in a wide range of requirements. However, we must begin somewhere, and Table 1 below provides a fair beginning point for a PBX with up to 15 phone extensions and 5 simultaneous calls.

For very light systems, lower specs than those given may work, however such a system will have very restricted capabilities. The advice for a basic installation should only be used for a test machine, as production systems should always have a margin of safety built in to account for peak load circumstances (50 percent ideally). Your overall system performance in terms of processing power and memory, not to mention bandwidth, should grow as the number of phone extensions and functionality grows.

Switch Requirement

Asterisk à Processor – Single Core, at least 700MHz, RAM – 1GB, Storage – 15GB

FreeSWITCH à Processor – Single Core, at least 1GHz, RAM – 2GB, Storage – 15GB

The majority of Asterisk PBXs are extremely light, allowing them to work on even the most basic equipment. We produced our PBX guidelines on a laptop from the early 2000s in part of our tests and had no serious concerns. This was, however, purely for testing reasons and not for use in a production system.

To perform properly, most FreeSWITCH systems will propose a more current system. A lighter system will suffice for testing, but FreeSWITCH-based systems are often intended to handle bigger loads, necessitating better performance and RAM. Most FreeSWITCH PBXs will recommend a current quad-core processor with a clock speed of 2 GHz per core, at least 8GB of RAM, and about 80GB of storage to ensure that the system functions well and has room to grow. Keep in mind that, depending on sampling rates and compression, recording conversations, voicemails, and system recordings for IVR menus requires at least 1MB of storage for every minute of recording on either platform. Depending on the amount of recording requested for each system, storage must be adjusted.

It’s also worth noting that, given the identical underlying hardware and software requirements, the widespread opinion is that FreeSWITCH can manage a far higher number of concurrent calls than Asterisk. Some have estimated a fourfold increase in concurrent calls, but it’s hard to believe this given that there appear to be no official testing methods in place and that much of the testing was done over 5 years ago. During this time, a lot of software was written.

Basic Functionality

Each switch has the majority of the same features at its most basic level. For either architecture, the process of creating extensions and gateways is very similar. Based on RAM and core performance, each system can support as many people as the underlying server can.

Both are built to make the most of SIP for connecting between network devices as well as other endpoints such mobile networks, VoIP systems, and the Public Switched Telephone Network (PSTN). Asterisk also has a dedicated interface for connecting to other Asterisk systems using the IAX protocol. FreeSWITCH has a unique clustering approach that not only increases the power of an implementation, but also provides redundancy in certain settings.

All Asterisk and FreeSWITCH systems come with modern phone functionality. Any FreeSWITCH or Asterisk-based switch on the market should provide voicemail, call recording, and IVR menus. Admins, superadmins, and users typically use portals to administer their respective feature sets using a secure web login.

Advanced Functions

The ability to provide multi-tenant (multi-customer) capabilities is perhaps one of the most noticeable characteristics of any FreeSWITCH system. Though a sophisticated Asterisk system can host several tenants, it is usually an expensive proprietary system developed on top of Asterisk (though Elastix has recently released an open-source multi-tenant version of its software). FreeSWITCH can serve several tenants on various domains or sub-domains, and these will function in a segregated manner, preventing a tenant from calling another tenant through an extension call.

Both systems can communicate with other platforms-based setups. Whether using the same exact platform or a different variety of the same underlying technology, Asterisk may efficiently interface with other systems (i.e. Asterisk). FreeSWITCH, on the other hand, offers strong interconnection capabilities, allowing individual systems in the cluster to perform numerous functions. Installing every role to a single server, much like in a Windows server setup, can be bad practice, at least for larger PBX deployments. Asterisk is rather set in stone at the core level, whereas FreeSWITCH allows each system in a cluster to fulfil a certain function.

More advanced communication functions, including as chat (instant messaging), video calling, and conferencing, are available with Asterisk and FreeSWITCH systems. Without an add-on, most Asterisk systems do not have IM capabilities (usually OpenFire, though others are available.) This module may need payment in some circumstances, while some systems, such as Elastix, incorporate OpenFire for free after activation. The only requirements for FreeSWITCH are the activation of the XMPP service and the proper configuration of devices that are allowed to use this functionality.

Both switches provide conference calling as a standard feature, so it’s difficult to pick a clear winner. Dial-in (meet-me) conferencing is supported by both Asterisk and FreeSWITCH. FreeSWITCH can be configured so that this duty can be handled by a single system. When this responsibility is placed on a “all-encompassing” FreeSWITCH system, resources are efficiently managed for a well powered computer. However, dedicating a single FreeSWITCH system to conferencing allows for much bigger voice conference scenarios, such as at the business level, when hundreds or thousands of individuals need to be on a company-wide conference call.

The way things are set up on a network varies a lot. Asterisk provides a number of endpoint management modules (such as IP phones and soft phones) that typically cost around $100 and provide provisioning software for a wide range of popular phones on the market. FreeSWITCH systems include various configuration files integrated into the platform for provisioning phones, although they are limited in comparison to Asterisk, and usually only support the most common kinds of IP phones from mainstream suppliers like Cisco and Polycom. However, it’s worth noting that FreeSWITCH is rapidly coming up in terms of auto provisioning.

It’s usually simple to connect either switch to the outside world via gateways. Both the FreeSWITCH and Asterisk systems include a number of example gateway configuration templates. Because Asterisk is a more established system, most SIP providers offer comprehensive documentation for connecting their system to an Asterisk gateway; whereas, FreeSWITCH has less documentation. If you’re having problems, a short call to your SIP provider will likely save you a lot of time debugging.


When comparing an Asterisk switch to FreeSWITCH in terms of functionality, there are little differences. End users will likely not notice much of a difference between any system implementation provided it is properly configured, though in my experience, I prefer the appearance and feel of the Graphical User Interface (GUI) for FreeSWITCH systems, such as FusionPBX.

Asterisk is considerably easier to work with on several levels. Because it is, in many ways, a forerunner to FreeSWITCH, the fact that the system is older (and well-received) means there is a lot more documentation, especially in terms of forums and user base. Because FreeSWITCH is a newer adaptation of a comparable concept, troubleshooting is a little more challenging because there are less technical instructions and fewer people to help. It should be noted, however, that the FreeSWITCH documentation is adequate and includes numerous examples of XML code.

Both systems are relatively simple to set up and use (especially if you follow our guides). Although Asterisk can run on low-cost hardware, FreeSWITCH-based systems tend to triumph when it comes to high-end PBXs that can manage a huge number of concurrent calls.

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