What is VoIP? How to choose the perfect system

A black headset lying on a desk with a phone receiver in the background

A business phone system may seem like a small thing, but it’s a little change that can generate a big result for your business. Whether you use it for sales calls, liaising with partners and distributors, or communicating with customers, some form of business phone network can give your business the boost you’re looking for.

Not only does a professional-grade phone system make a small business appear more impressive to customers, it also shows how seriously you take your business. Outdated voicemails and one main phone line that no one answers do nothing for your brand image.

A traditional landline, however, is no longer as viable with our new ways of working. Many businesses were already choosing to use Voice over Internet Protocol, or VoIP, and now, with so many of us working from home, this software is an ideal choice for a company phone setup.

You’ve probably already used VoIP for personal or business uses - think Facebook Messenger, WhatsApp, or Skype. You only need an internet connection to make and receive calls, whether through app-based ‘softphones’ or additional headsets or handsets that work just like normal phones.

VoIP offers a range of benefits over traditional phones, though, as they’re easier to manage, less expensive, don’t require physical equipment and installation, and allow your employees to work from anywhere. VoIP systems usually include enhanced functions as well, such as smartphone integration and advanced call handling rules. And as your business grows, it’s cheap and easy to upgrade your telephony system.

As plenty as the advantages of VoIP are, however, you don’t want to jump to a decision too quickly. There is a huge range of services to choose from, so here are a few key things to keep in mind while you shop around for the internet phone package that best suits your needs.

Is your broadband up to it?

Before implementing a VoIP system, you will need to ensure your internet connection is fast enough for voice calls. Generally, one VoIP telephone call will use around 90-100Kbits/sec of bandwidth, both downstream and upstream.

To test if your connection is fast enough, you can use one of the online VoIP speed-quality tests available such as myspeed.visualware.com or voipreview.org.

If your internet connection is already pushed to the limit, then you must upgrade it. A lack of bandwidth will quickly turn VoIP calls into garbled mush that certainly won't do your business any favours.

If your office has a lot of people using the internet at once, consider getting a second line dedicated to VoIP traffic to guarantee you won't have connection issues. Consider ordering a backup link as well if phone calls are central to your business.

The other technical prerequisite is a suitable router. An on-site IP PBX needs port-forwarding rules configured in your router to allow external users to access it. The router must support quality of service (QoS) rules for prioritising VoIP traffic. If it has a SIP ALG (application layer gateway), turn it off to avoid potential instability issues.

What's in the trunk?

To make your VoIP system useful, you'll need to sign up with a SIP (session initiation protocol) trunk provider that can link the public telephone network with your internal IP PBX.

It's up to you how many SIP channels you need: each VoIP call uses one channel, so check the number of staff using their phones during the busiest periods to determine how many you need.

Don't forget that callers on hold and queued calls still consume a SIP channel - and you may have mobile users running VoIP software on their smartphones to consider as well. If you're still unsure, a good rule of thumb for moderate phone usage is one SIP channel for every three users.

While there is a large range of providers to choose from, it's important to check their pricing schemes as these can vary widely. Ensure that you can upgrade easily, or even downgrade, the number of channels purchased.

Don't forget to check that you can have local phone numbers assigned to your SIP trunk, and find out if you can have multiple numbers, which your IP PBX can then route through to different extensions.

On-site or hosted

If you decide to install an on-site IP PBX system, don't be tempted to take shortcuts. VoIP is a mature technology, but there are several pieces to the puzzle that all need to be properly configured before they will talk to each other.

Treat the switch as a fully documented, fully funded IT project, and host your PBX on server-grade hardware dedicated to only this task. While this may not seem technically necessary, don't forget that you're creating a single point of failure that will take your entire VoIP system down if there's any conflict with other services running on the same host, or if it goes belly up.


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Another important tip is to never configure an IP PBX to use a dynamically assigned IP address. These can change at any time, and if yours does then all your port-forwarding rules will fail, and your IP phones will no longer be able to access the PBX.

For smaller businesses with limited IT expertise on-site, it makes sense to consider a cloud-hosted VoIP solution instead. This will cost considerably more than running your own server, but with the right service-level agreement and support contract in place, you can avoid the danger of something going wrong and save yourself plenty of upheaval.

Hanging on the telephone

The sheer range of features offered by a VoIP PBX can be overwhelming. Before going live, set up a test system and play around with it to make sure you understand how it works.

One typical call-handling feature you might want to make use of is a "digital receptionist" to read out a menu of options: "For accounts, press 1; for sales, press 2," and so on. This exudes professionalism.

You can also set up call redirection, so that incoming calls can be automatically routed to staff who may not want their mobile number made public, or to those on the road. And when it comes time to choose handsets, there are endless options to choose from. Mobile users can also use "softphone" apps on their own phones, but these aren't always included in the IP PBX price.

A well-implemented VoIP system will save you hard cash with cheap local and international calls and give your business a professional image. Call-handling features that were previously beyond an SMB's budget can be set up cheaply and easily.

Dave Mitchell

Dave is an IT consultant and freelance journalist specialising in hands-on reviews of computer networking products covering all market sectors from small businesses to enterprises. Founder of Binary Testing Ltd – the UK’s premier independent network testing laboratory - Dave has over 45 years of experience in the IT industry.

Dave has produced many thousands of in-depth business networking product reviews from his lab which have been reproduced globally. Writing for ITPro and its sister title, PC Pro, he covers all areas of business IT infrastructure, including servers, storage, network security, data protection, cloud, infrastructure and services.