How much bandwidth do I need for VoIP?

Businesses throughout the UK are replacing old legacy phone systems and replacing them with voice over IP (VOIP phone system)telephone systems.

One of the key steps in successfully moving to a VoIP phone system, is being able to accurately plan for the amount of bandwidth or data you will need. If you don't allocate enough bandwidth capacity to your VOIP system the calls will degrade in quality rendering the system useless.

How much bandwidth do we need to support our VOIP phone system? This is one of the questions we are asked every day by our prospects and customers.

What are concurrent calls and why do they matter?

The first thing you need to understand is how many people do we have in our business on the phone at the same time.

The number of staff making or receiving calls at the same time is known as the number of concurrent users.

So, if you have 25 staff and the maximum number of people that will be making or receiving calls at the same time is 15, then your business will need to support 15 concurrent calls. 

This is important because you will need to ensure you have enough bandwidth to support 15 concurrent VOIP calls.

How much bandwidth does each concurrent VOIP call need?

The second thing you need to understand is, how much bandwidth do I need to reserve for each concurrent call?

The exact amount of bandwidth each VoIP call uses is very much dependant on the type of voice over IP phone system you choose to use. Nevertheless there is a rough rule of thumb which is that each concurrent call requires 100 Kilo Bytes Per Second (Kbps) of upload and 100Kbps of download per call.

So if you have a requirement for 15 concurrent calls you should allocate a minimum of 100Kbps x 15 = 1.5Mbps of upload and download bandwidth to support this volume of calls.

The following table can help you spec the amount of bandwidth you will need to allocate to VOIP in your business:

How to perform an internet speed test for VOIP? 

Now you understand the amount of bandwidth you need, the third step is to test your current data connection.

VoIP means your business is solely reliant on your data connection for voice calls as well as data access. It is imperative therefore that you have enough capacity to support both the call and data needs of the employees in your business.

If you have 20 concurrent calls in your business the recommended minimum bandwidth is 2 Mbps upload and download, ideally you would allocate 5 Mbps upload and download.

It is important to check the speed of your internet connection because the advertised speed of most connections (unless it is a leased line) is faster that the speed in reality. The easiest way to test your internet speed is to head over to M-lab and run a speed test. You should make sure that your speed is fast enough to support your VOIP calls, as well as internet browsing, cloud applications, email and other applications. If you do not have enough capacity your call quality will fall, calls may drop or become unintelligible. 

How can I prioritise VOIP on my network?

It is possible to prioritise VoIP traffic over less sensitive data traffic such as web browsing, and email.

There are several ways that traffic can be allocated:

1. Quality of Service - by enabling quality of service (QOS) you can tag each data packet on your network with a priority. This way you can ensure that VOIP traffic is prioritised above web traffic across your network.

2. SD-WAN - a software defined WAN allows you to add QOS to your network even if you are using the internet to create your network. If you don't have an MPLS network an SD-WAN can work really well. 

3. Router - Some routers can prioritise VOIP traffic, make sure your network router’s Quality of Service (QoS) settings are as follows:

• UDP/5060 – Priority: High
• UDP/6060 – Priority: High
• UDP/16384 to 32768 – Priority: High

Amvia have a team of highly skilled business VOIP experts ready to help and advise you. We do this every day so please get in touch and tap into our knowledge. We are here to help you find the right VOIP soultion for you business so get in touch now!