The Benefits of Choosing a Virtual PABX

With multiple Advancements in modern day PABX technologies, one growing trend on the industry is Virtual PABXs.

Although the technology is transparent on the subscriber side, it has been around for a couple of years and has been a backbone for major VoIP industries.

In this article we will be looking at the technology, its uses, structure and its advantages as an ICT infrastructure solution.

What is a Virtual PABX?

Virtual PABX is a PABX system which is mostly logical in form, meaning majority or all of the component structure is software based. These PABXs can be located locally or hosted remotely by a hosting service on the public network.

With the rapidly increasing speeds in modern day data communications, this makes it possible to have telephone subscribers on any endpoint of the public network and host them on a central Virtual PABX.

In some deployments, Virtual PABX is a part of clusters of application servers in a network.

What Is The Difference Between Traditional PABX and Virtual PABX structures.

The difference between a traditional PABX and a Virtual PABX lies in its structure, below is an explanation on how the two vary.

Traditional PABX(IP enabled) structure

A traditional PABX build usually contains a single central controller with multiple integrated peripheral equipment to form a PABX structure. These IPE’s or components perform various logical functions/tasks for the system. For example,

Traditional PBX Components

On the diagram above, we can see that aside from the central controller(Call Server), we have a registration server to handle IP based registration, a media gateway that is mostly equipped with digital signal processors and a line gateway to connect to end devices.

These components/parts are usually proprietary(vendor-specific) so every hardware must be purchased to build the functions of the PABX.

Although, builds may vary from vendor to vendor(modern builds usually have them built on one integrated equipment) the principle of using a specific equipment still stays true.

Virtual PABX Structure

The structure of a Virtual PABX differs because only the system software of the traditional IP enabled PABX is loaded on a Virtualization Platform, thus performing all the installed system software functions.

Some of the previous component functions are also integrated in the system software reducing the need for additional parts.

Virtual PABX Diagram

The Virtualization Platform then resides on the host controller, which is your typical blade/tower server equipment. You can put clusters of Virtual PABXs and various application servers on the host controller if your server equipment can support the load.

Virtual PABXs are IP-Based, meaning they are intended for IP-Phone/Softphone based deployment. Although it is still possible to use traditional PABX functions such as digital trunks, TDM Phones or Analog Phones, additional interface equipment is required.

Hosted Virtual PABX

As in many cases you only need a server and the base system software to run a fully functional virtual PABX, It is flexible enough to host them in the internet (public network). The diagram below shows a simple diagram of a Hosted Virtual PABX.

Sample Virtual PABX Infrastructure


In the diagram above, the Virtual PABX is hosted on the server equipment on a primary location, this maybe your VoIP Host Provider. On another location (secondary location) the server configuration is mirrored; this will serve as a backup in case your primary controller goes down.

This backup server can also be another server that can be clustered to form a PABX network. Subscriber endpoints (IP Phones) can exist on any part of the internet, allowing a private communication network across multiple locations.

In addition to, Signaling Data is sent between the controller and the IP Phone, while the voice data is sent between two phones. Audio streams are sent in between subscribers therefore the controller does not shoulder the bandwidth. Typically, this configuration is the same for most VoIP messengers you often use, although they have those VoIP clients as endpoints.

The Benefits Of Using A Virtual PABX

Reduce Installation, Maintenance and Equipment Cost

  1. By using a hosted virtual PABX, you can reduce eliminate the cost of installation and equipment
    You can just pay for the services on your provider (which is minimal as 1 powerful server can host multiple virtual pabx ), and have low maintenance fees on your side(the only thing you may have to maintain are the IP Phones). If you’re building your own Virtual PABX network, overall cost is still lower since less equipment, upkeep and configuration is needed.
  2. Link multiple offices in almost all locations
    With the use of internet you can link multiple offices even if they are on another region. Since calls are made by VoIP, long distance and international charges are eliminated. The only thing you have to pay for is the internet service. This is completely beneficial when you have/outsource your call center department on a separate location. One thing to note is this is also true on the traditional PABX; however, deployment of a multiple site PABX is of course costly.
  3. Easy replication
    Probably one of the best things about Virtual PABXs is how you easy can replicate them, allowing an easily accessible form of restore when something goes wrong or a fallback to another site when the primary site goes down.
  4. Vendor Support
    Most of the Major PABX Vendors have released Virtual PABX packages for their IP-Based PABXs. These in turn assures you that support and software updates are always available from your vendor. Some of the National Switch (Exchange) in ASIA is also virtual in nature (mostly from Huawei) which basically shows how powerful the systems are.

Virtual PABX, Author’s Notes

With the IP-PBX trend booming, more and more companies are replacing their previous TDM PABX (Time Division Multiplexing, A term for Digital PABX) with a Virtual counterpart.

Being IP-Based, deploying a Virtual IP-PBX leaves you a lot of advantages and expands your options for future unified communications.

These PABXs also offer wide support SIP (Session Initiation Protocol) which is a widely used VoIP standard providing you with more options other than your IP Phones.

From an IT systems admin perspective, a virtual PABX system is easy to install, quite robust and easy to manage, critical points to consider if you’re planning to build one.