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Ron Callari

October 26, 2015

Is Your Internet Fast Enough For VoIP?

The rundown on bandwidth, speeds, and the real requirements for VoIP calling.

If you’re thinking of moving from landline to VoIP, might be asking if your internet connection is sufficient for VoIP. The answer might surprise you. VoIP phone services can work in places with slower than average internet speeds. In 2019, line speed is arguably the least relevant factor to call quality. Unless you’re on dial-up, you’ll likely have enough speed for all the calls you’ll ever make.

If you’re still concerned and want to understand more, this article outlines the factors to look into before you fully commit. Read on, and we'll give you the rundown on bandwidth, speeds, and the real requirements for VoIP adoption.

What is Bandwidth?

Bandwidth refers to your Internet service's rate of data transfer—or how fast it can send and receive information within a specific timeframe.

That doesn't necessarily mean VoIP requires a ton of bandwidth to ensure high-quality audio. But it does mean that you'll need to reserve a share of bandwidth for your VoIP system, and from there, assess whether enough is left over to perform other critical tasks.

To understand why bandwidth is a factor for VoIP, you need to understand its role.

Bandwidth is generally measured in terms of megabits per second (Mbps or Mb/s).

This unit is used to describe the transfer rate of data of X megabits (megabits) for each second of time.

High bandwidth means faster transfers.

It's also worth pointing out that many routers allow you to prioritize voice calls on your data network, preventing other applications from having a negative impact on your call quality. You'll need to check with your ISP to find out if this is an option.

What is a Codec?

The required bandwidth for your VoIP service typically depends on two things. The first is the number of concurrent calls that your business will be making, and the codec that your VoIP provider uses.

So, what is a codec?

A codec, also known as a coder-decoder, is a program or device that can encode a digital data stream for transmission, then decode the data stream for playback. In other words, the codec essentially compresses and decompresses data to shrink digital information and allow for faster transmission.

Without codecs, data transfers could be up to five times slower. Suffice to say; they're pretty important.

With VoIP, a codec is used to convert audio voice signals into compressed digital data, ready for transmission. And then, back into uncompressed audio signals that are ready to be replayed.

Related: Beginners’ Guide to IP Phones

VoIP Codec Protocol

For most standard codecs, your business will typically need a bandwidth of 85-100kpbs per each call happening at a time.

Your business can assign different codecs to select phones, depending on company preferences and priorities. For example, the legal department or boss of the business can use a higher-level codec, if necessary, compared to the codec that employers use.


Most providers will usually support G.711, as it is the standard codec used for most VoIP systems.

G.711 works best for companies that have a lot of bandwidth, due to its 64K bitrate and its compression of 1:2.

That said, it may be the best bet for most users, providing high-quality audio without eating up a ton of bandwidth.


Opus is a newer codec option, quickly becoming the go-to for VoIP users. Opus requires a smaller amount of bandwidth, depending on the settings that your business makes, and uses bandwidth as little as 6 Kbps up + down.

Telzio supports this advanced codec option, ensuring business VoIP users have optimal quality on calls.

Related: 5 FAQs about VoIP Phone Systems for Newbies

Minimum VoIP Bandwidth Requirements

What are the minimum VoIP bandwidth requirements? Again, it's hard to come up with a hard number. Your bandwidth requirements depend on the number of calls your business can expect to make at any given time. It also depends on the amount of bandwidth used by your other services and apps, and your Quality of Service Settings (QoS).

Typically, G.711 requires 87 Kbit up + down for a single call, while Opus requires as little as 6 Kbit up + down.

A speed testwill allow you to quickly get a sense of your bandwidth and latency, while also revealing your VoIP capabilities. You'll want to test your connection to see how many phone lines your set-up can support without impacting sound quality.

You'd typically need about 80kbps to make a call, though faster speeds won't make much of a difference in terms of sound quality.

However, more bandwidth means there's more capacity to run multiple programs at once. For example, it comes in handy if you're surfing the web while talking to a prospect or referencing a report during a client call.

Why is Good Bandwidth so Important?

Having high bandwidth is essential for businesses to ensure high-quality calls.

VoIP systems are internet-based, so to question your internet speed is understandable.

The quality of your VoIP call, for the most part, depends on having enough bandwidth to support multiple calls at once without slowing your other business functions.

Your bandwidth is not always the problem or the solution when it comes to the quality of your VoIP calls.

If you have sound quality issues with VoIP calling, there are settings that will help to ensure optimal VoIP voice quality.

Related: 5 Ways to Troubleshoot WiFi Issues with VoIP

Bandwidth vs. Ping Time

Bandwidth and ping time are two different things. Bandwidth is the throughput of your internet connection, whereas Ping Time is the roundtrip time of a data packet from the phone to the server and back again, measured in milliseconds.

For example, your ISP might offer a good amount of bandwidth. However, if the phones are far away from your servers, or some obstacles stand in between them, it might compromise your call quality. This is because your VoIP call relies on fast delivery of data in both directions.

Ping vs. Download vs. Upload Speeds

A ping represents the reaction time of your connection. Or, how fast you can get a response after sending a request. A fast ping means a more responsive connection, especially in applications where timing is everything (like video games).

The download speed is how quickly you can pull data from the server to your screen. Most connections are designed to download much faster than they upload since the majority of online activity, like loading web pages or streaming videos, consists of downloads. Download speed is measured in megabits per second (Mbps).

The upload speed is used to send data from you to others. Uploading is necessary for sending big files via email, or in using video-chat to talk to someone else online (since you have to send your video feed to them). Upload speed is measured in megabits per second (Mbps).

How to Calculate the Amount of Bandwidth You Need

The share of bandwidth in use during a call will impact quality if there are too many things going on at once.

Again, a speed test allows you to quickly get a snapshot of your bandwidth and ping time, while also providing some insights into how these factors impact your VoIP capabilities.

The bandwidth that is required by your company for your VoIP service together with other company systems, depends on multiple things, including the following:

  1. The speed that your Internet service provider (ISP) delivers for uploading and downloading data.
  2. Other services or applications that are currently also using your data network and the amount of business bandwidth that they use.
  3. The Quality of Service (QOS) settings that your router provides so that you can optimize for your VoIP system.

For the most part, minimum bandwidth depends primarily on your codec.

As mentioned, G.711 has long been the VoIP standard, and it uses 87.2 Kbps. Opus, on the other hand, requires as little as 6 Kbps up + down per call.

Here's a breakdown of how much of a difference exists between the G.711 and the Opus:

1 Mbps = 1,000 Kbps = 11 live G.711 calls = 166 live Opus calls

1 Gbps = 1,000,000 Kbps = 11,467 live g711 calls = 166,666 live Opus calls

As you can see, the Opus codec supports 15 times the number of calls as G.711 on the same bandwidth.

Telzio is the leading VoIP provider using Opus.

Remember, both upstream and downstream bandwidth is required to complete a call (you send and receive audio). Meaning, your connection’s capacity is always dictated by the lowest denominator. In most cases, the upload speed is the slowest.

Quality of Service (QoS)

One way to ensure Quality of Service (QoS) is to enable QoS settings.

Quality of Service (QoS) settings allow you to prioritize the voice calls made through your data network and prevent other applications from interfering with sound quality.

This function allows you to prioritize your internet connection’s data, and set it, so it makes sure you always have space for VoIP calls. In this case, QoS slows other applications in use at the same time.

Disable SIP Application Layer Gateway (ALG)

SIP Application Layer Gateway (ALG) is there for preventing and modifying some of the issues that are caused by router firewalls via the inspection of VoIP traffic.

Most routers will have SIP ALG turned on by default. The problem with SIP ALG is that it sometimes modifies SIP packets in ways that corrupt them. This creates SIP packets that are unreadable and can cause issues in regard to registering incoming calls. If your business is experiencing such problems, we recommend disabling SIP ALG in your router.

UDP Settings for VoIP

By default, phones use UDP, which is optimal for both network and servers, since it requires fewer resources. However, sometimes, TCP may work better depending on the customer’s system and settings. Telzio also offers the option to use TLS, which is encrypted signaling over TCP.

Making VoIP Calls on Mobile Phones

As mobile Internet connections have become faster and more accessible, the quality of mobile VoIP calls has also improved dramatically. While the quality still depends on the connection, you may find that in major cities, you will have plenty of bandwidth to make calls.

Remember that when you make calls from your cell phone, you will only be making one simultaneous call.

All you need is a stable 6 kbps connection to make a VoIP call using your mobile data. Most 4G LTE connections are between 5 Mbit (5,000 Kbit) to 50 Mbit (50,000 kbps).

However, you may hear a slight delay in the audio at times. The reason being, your mobile data connection depends on how many people are accessing the network at the same time you are.

And, as with wired connections, the time of day can also affect speeds. For instance, you may see slower connections during lunch in a bustling business hub. By contrast, speeds may be much faster on a Sunday morning, when no one else is around.

Final Thoughts

Ultimately, low-bandwidth doesn't mean you can't use VoIP. If you want to be sure, here are the questions you should be asking:

  • How much bandwidth do you receive from your ISP?
  • How much bandwidth do your essential business apps use?
  • How many calls do you expect to make at a time?
  • What kind of codec does your VoIP provider use?

The only way to truly find out if your internet is sufficient for VoIP is to do a test. With the Telzio Mobile App and Webphone, you can make plenty of test calls at no cost.

Learn about the leading business VoIP service from Telzio.