I’ve been writing about IT, and about technology in a wider sense, since 1982, and yet I am still no kind of technical expert. Sometimes, when invited by a new client to work on their blog, I’ll suggest we do the first post as a one-off assignment, giving myself an opportunity to make sure that I’m able to deliver the level of technical depth their blog strategy requires. In this post for SME businesses on making the best choice of VoIP infrastructure, I’ve worked in a knowledgeable but non-presumptuous voice, imagining that the reader is smart and interested, but probably not technically expert. Blog post for voice, WAN and connectivity solution specialist Spitfire.

completed: 2022
*If no image of the finished project is available, my presentation document is shown.
*Thumbnails of some older projects were uploaded at resolutions which may now appear out of focus.

Choosing an internet circuit to support VOIP

With the possible exception of your office coffee machine, there’s nothing more likely to cause frustration or disrupt productivity than a VOIP system that comes between your users and the making of clear, consistent calls.

With the financial and functional benefits of VOIP clear to the majority of SME businesses, the challenge of getting voice packets from your handset to that of the person you’re calling in a regular, timely and consistent fashion, is paramount.

The journey these packets have to make is hazardous. From your handset, they travel across multiple networks, onto the telephony networks, with return packets completing the journey in the opposite direction. Failure at any point means your team are trying to do business against a backdrop of distortion, dropped out words or even disconnection.

If you’re trying to take full advantage of VOIP, therefore, and expect to enjoy clear calls with robust connectivity, it’s important to make good choices and set up your connectivity carefully, so that you control the journey the packets take.

How to ensure the route supports good quality VOIP

Ideally, your Service Provider and VOIP Provider will be one company. This will provide direct connectivity to the telephony networks without adding in the performance uncertainty of voice packets hopping around the public internet. We’ll assume for these purposes they will ensure your call packets are handled competently onwards from them to the person you are calling, and that the packets being returned to them from the other end will also be handled efficiently.

At your end, between you and your Service Provider (the part known as the Access Circuit), the key decision you must make is over the nature of your VOIP network. As in most things, this presents a ‘cost versus performance’ decision for you to take. The good news, however, is that unless your business requires the most business-critical VOIP performance, there are excellent options that are both effective and affordable.

The four key considerations for a VOIP network

Four factors determine the quality of call experience a VOIP Access Circuit will deliver. These are Bandwidth; Latency; Packet Loss; and the delivery speed variance known as ‘Jitter’.

• Bandwidth of around 100 Kbps is required, both upstream and down, to provide call consistency. Obtaining this should provide little difficulty.
• Latency, the time taken for a voice packet to get from your phone to the phone you are calling, should be under 150 ms to avoid audible delays in the conversation.
• Packet Loss causes gaps in speech, or actual dropping of the call. This should be kept below 1% for acceptable performance.
• Jitter is a variance in latency which results in packets arriving in irregular pulses, rather than in the nice steady stream required for a clear, undistorted call. This should be below 45 ms to avoid what’s known as ‘broken audio’ – the effect that imparts the effect of scuba divers talking to your call.

The differences between the options available to you for your Access Circuit are, in effect, the difference between the measures each has in place to protect your voice packets on their journey.

The four core types of Access Circuit

Let’s start with the two extremes: the highest and lowest quality options available to you.

• Dedicated Fibre Circuit.

This is the gold standard of Access Circuits, and what we term at Spitfire Network Services as ‘Voice Approved’. The circuit is dedicated to you, meaning there’s no risk of congestion from other parties. By combining it with a premium backhaul service you are guaranteed that all your bandwidth will be available and the targets for latency, packet loss and jitter will all be met.

The only precaution you need to take is to add a Quality of Service (QOS) policy on your own router, and to get your Service Provider to do the same for the downsteam traffic. This will ensure you don’t congest your own circuit with too much non-VOIP traffic no matter how much video streaming or large file download is also going on. Your service should be defined for ‘Consistent Performance’ by your Service Provider in their SLA.

Watch out for Fibre Ethernet offers that do not provide this level of performance guarantee, as these can cause problems for quality of VOIP.

• FTTC/FTTP Broadband

FTTC (Fibre to Cabinet) and FTTP (Fibre to Premise) Broadband use shared Access Networks and often congested backhaul, resulting in reduced bandwidth, increased packet loss, and higher latency at busy times.
You are unlikely to be able to secure SLA-backed performance meeting the standards needed for reliable VOIP, and so we view this as ‘Unsuitable for Broadband.’

There are two other options available to you , each sitting somewhere between these:


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