Troubleshooting bad call quality

The most common issues experienced with VoIP are choppy or garbled sound and delay. We find that most issues are related to the user’s internet connection, sometimes called ‘last mile’. We will touch upon the most common sources of problems below and guide you step by step in troubleshooting the potential cause. This page is meant as a starting point and is by no means comprehensive. Please contact us if you require further assistance. We’re here to help.

Choppy sound

The most common issue when experiencing suboptimal call quality is choppy sound. This occurs when the data packets carrying voice are lost (packet loss) or get delivered in the wrong order (jitter), resulting in garbled sound.

The most common source of jitter is insufficient capacity or congestion of your internet connection resulting in insufficient bandwidth to effectively transport your voice data packets. This can be due to the fact that:

  • your internet connection is too slow;
  • your internet connection is flooded by uploads or downloads from other devices;
  • your internet provider is temporarily providing less bandwidth.

Slow Internet connection

If you are consistently experiencing choppy and/or garbled sound, chances are that your internet connection speed is insufficient. An HD VoIP call uses about 0.1 Mbit/sec of bandwidth. As a rule of thumb, it is wise to have at least double the amount of capacity available at any time per concurrent call. E.g: If a maximum of three colleagues are on the phone at any given time, you should have at least 0.1 x 3 x 2 = 0.6 Mbit/sec of upload speed AND download speed fully dedicated to VoIP. This is in addition to the data consumed by other devices on your network, such as PC’s.

To get a snapshot and indication of your real connection speed – not the speed that your internet provider has promised you – do a speedtest. To get a good idea of consistent speed, do a few tests at different points of the day and days of the week. Especially when everybody is in the office and you are experiencing slow internet and/or call quality issues.

Solution:

  • Upgrade your internet connection. Make sure you have plenty of spare capacity. Faster is always better.
  • Even better, split VoIP data from computer data: get a separate connection for VoIP.
  • Use a higher compression technique for your calls. (The G729 codec instead of G711a)

We are happy to help: please contact us for further assistance.

Flooded Internet connection

Even if your internet connection is providing sufficient bandwidth, you might still experience call quality issues due to the fact that other devices are consuming all the data, leaving too little spare capacity for voice data packets to be transmitted and received efficiently and effectively.

Solution:

  • Ask your colleagues to upload and download large files when you are not on the phone.
  • Switch off or limit the speed of applications that synchronise large files, such as Dropbox and Google Drive. Even the fastest connections can get flooded quickly.
  • Set QOS (Quality of Service) on your router and prioritise VoIP traffic and or all traffic to and from the IP range 195.35.114.0/23.
  • Upgrade your internet connection. Faster is always better. Keep plenty of spare capacity.
  • Split VoIP data from computer data: get a separate connection for VoIP.

We are happy to help: please contact us for further assistance.

Temporary reduction in bandwidth provided by your internet provider

Your internet service provider (ISP) might be providing less bandwidth than normal. This can be due to congestion, often in peak times when your neighbours are heavily using the internet. To confirm the speed of your current connection do a speedtest.

Solution:

Contact your ISP and ask them if they are experiencing network issues and/or congestion. Some providers can prioritise your traffic over others and/or improve the contention ratio.

Another reason your ISP is providing less bandwidth than normal could be that your connection is being ‘shaped’ or ‘throttled’. A strategy often used by internet service providers on uncapped contracts.

Shaping

Shaping means that the priority of certain traffic is demoted. Most commonly; torrents and downloads of other large files. Some providers also demote VoIP traffic, resulting in insufficient capacity for voice packets.

Throttling

Throttling means that an internet connection can be slowed down during certain times of the day or after you have hit a certain download limit. You still have an active internet connection, but the speed is heavily reduced. Resulting in slow internet and call quality issues.

Solution:

Contact your ISP and ask them if they are shaping or throttling your connection in any way and specifically VoIP traffic. Ask them if they can prioritise VoIP traffic and/or offer a contract that is unshaped and unthrottled.

We hope to have provided a good starting point to find the cause of potential VoIP call quality issues. Should you require further assistance, please do contact us. We are happy to assist.

More reads

5 Curable Causes of Poor VoIP Call Quality

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