Choosing an internet circuit to support VoIP

Dominic Norton, Sales Director
25 March 2022

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.

  • Voice Assisted FTTC/FTTP Broadband

You can obtain Voice Assistance with some kinds of FTTC/FTTP circuit. This enables some of the features of the backhaul network to be used to configure various QOS mechanisms across a normal broadband circuit, giving voice packets a rather improved chance of reaching their destination.

There are limitations to what can be achieved in this way, however. Packets can be protected downstream, but QOS mechanisms will have no effect upstream until the packets have passed through most of the network. As it is mainly downstream that congestion occurs, however, this approach will deliver a solution that is adequate for many businesses.

The limitations of the internet do mean that service levels cannot really be guaranteed, and so performance SLAs are virtually impossible to obtain for this type of circuit. Notwithstanding this, Voice Assisted FTTC/FTTP Broadband is suitable for non-critical VoIP, making it worthy of consideration by small businesses for which VoIP is important but not business-critical.

  • FTTC/FTTP Ethernet

FTTC/FTTP Ethernet combines the low cost of broadband with the performance of an ethernet level backhaul network, to give a ‘Voice Approved’ circuit that in many ways represents the best of both worlds.

Ethernet backhaul makes it possible to provide SLA-backed QOS mechanisms on all or part of your contracted bandwidth. These circuits do require careful router and ISP configuration, but then offer the best value ethernet connectivity, making them ideal for small and medium businesses where VoIP is critical, or where other applications that require consistent performance are also in use.

As the cost of an FTTC/FTTP Ethernet circuit is little more than that of a broadband circuit, this is a very popular option for many SMEs.

Making the call

Making a decision on the right solution for your business, should not prove too difficult. As we have said, this will usually come down to balancing performance with affordability, but depending on the nature of your business it should be possible to get outstanding VoIP performance suited to your need at a price that is affordable. In summary:

  • FTTC/FTTP Broadband – In almost every case, this is not suitable for a VoIP access circuit.
  • Voice Assisted FTTC/FTTP Broadband – You’ll have no performance SLA, which is never advisable, but if you have a low use/non-critical VoIP need, this may do the job.
  • FTTC/FTTP Ethernet – This is an excellent solution for all but the most critical VoIP needs, and will come backed with an SLA.
  • Dedicated Fibre Circuit – The costliest, but ultimately the best of all options. Dedicated circuits mean no congestion, with rugged performance SLAs in place.

Our advice is always that, if you’re looking for a circuit to support VoIP, you should choose one with an appropriate SLA. Any option that does not offer this is likely, sooner or later, to result in voice quality issues of one kind or another.

Get in touch. If you’d like guidance of any kind about choosing the right internet circuit for your business, we’re here at Spitfire Network Services to help.