How Quality of Service can affect your VoIP Calls (and what to do about it)

If you’re using VoIP or SIP trunks, there are a number of factors that can impact the quality of your calls. Many of these have nothing to do with your PBX system or the quality of your VoIP or SIP service.

If a web page loads slowly because you’re downloading a large file, the pauses in your internet speed are usually unnoticeable. But with internet phone calls, these pauses can cause an interruption to your phone call quality.

First and foremost, having a good internet connection is essential to making sure your calls are clear and uninterrupted, however, that’s not all there is to it.


Where does Quality of Service fit into the PBX puzzle?

Before we get into what Quality or Service is, it’s important to understand what it isn’t. This means understanding a little about breakpoints and bandwidth, both of which can impact your calls. Knowing this information means you can rule other issues out before deciding that QoS is the reason for your drop in call quality.


Breakpoints are all of the different locations where a fault can occur in your phone service. Think of the way your plumbing is connected to the public water plant. There are pipes within the plant itself, public pipes and connections, t-sections where the pipe moves from the mains to your house, and pipes to every different tap in your home. When you turn on your tap and there’s no water, the fault could lie in any of these places (probably more, but we’re not plumbers 🙂

Telecommunications breakpoints work in the same way. There are breakpoints in the public network and inside your premises, from the wall outlets, your PBX system, your modem, and your wall outlets. Breakpoints can impact your call quality and, depending on where they are, finding a solution could be the responsibility of your VoIP service provider, your VoIP service carrier, or your IT team.


The amount of data that can be transmitted through your internet connection in a set amount of time is known as bandwidth. Yes – this one is all about your internet connection.

You will see bandwidth expressed a MBPS (megabits per second). Your connection will have a upload bandwidth (speed of data you send out), and a download bandwidth (speed of data that’s incoming). When you selected which internet connection to get in your office, there would have been a maximum bandwidth included. It’s usually referred to as ‘connection speed’. For example, you may have a plan with a 100g download limit with a connection speed of up to 12/1 mbps.

When you connect your PBX system to your internet connection, each call will be taking from your maximum bandwidth. If it’s sharing the load with your general internet use, it could put pressure on your bandwidth, and you could experience interruptions and a drop in call quality.

Your service carrier should have discussed your phone and internet use before you signed up for a plan. Often, a single data connection will be able to carry your internet and your phone calls easily. But if it can’t, the best solution is to have a dedicated data service for each. That way, your phone and internet run each on different services, and the use of one will never affect the quality of the other.

What is Quality of Service?

When your call quality drops, the problem could be one that is beyond the power of your phone system provider. It could also be out of the hands of your SIP service carrier, and even your resident  IT guy.

These factors are referred to as Quality of Service (QoS) and are concerned with the finer details about how the internet works, and how your devices connect to others.


Latency refers to the time it takes for data to travel from one point to another. When you visit a website, download a video, or send an email, latency refers to how long it takes your computer to connect to the source, and retrieve their data for you to access.


Ping refers to the reaction time of your connection, kind of like the way the reflexes in your body work. It measures, in milliseconds, how long it takes for you get a response after you’ve sent out a request. The faster the ping, the better the reaction time of your connection.

The number of breakpoints your service travels through will influence the speed of your ping.


Devices use packets to communicate with each other over the internet, they use packets. Packets are, put simply, chunks of data sent back and forth.
If device A sends a packet to device B every 10 milliseconds (ms), and device B is sending packets back at the same rate, there is no jitter.

However, if device A is sending packets every 10ms, but device B is busy downloading a large file or video, it may not be able to receive the packet you’re sending in the same timeframe. In this case, it might get zero packets for 60ms, and then get 6 packets all at the same time.

Now, this doesn’t matter if you are browsing websites of checking your email, because 60ms is no time at all. However, every millisecond counts in a phone call. You WILL notice the interruption, no matter which end of the line you are on.

Finding a Solution

The root of QoS issues lie in the wide expanses of the internet. They cannot be repaired by your phone system provider, the carrier of your SIP service, or by your IT guy.

While it’s important that you eliminate other possibilities first, one step closer to a solution is to have a dedicated internet connection. This would exist solely for the purpose of carrying your phone calls. This way, general internet use in your office will never have any impact on your call quality.

If you’re setting up VoIP or SIP in the near future, getting the right provider is an absolute must. We recommend SpringCom because we know that their priority is the same as yours. That is, ensuring that your voice and data services work for your business. They also tailor their phone plans to suit your needs. You can get in touch with them on 1300 857 194 to find out more about switching your PBX system to a SIP service.