Understanding QoS on VoIP Phones
Learn more about QoS and how you can identify and troubleshoot audio issues that are caused by poor QoS.
Written by Val Campos
Updated at July 10th, 2026
Table of Contents
What is Quality of Service (QoS)?
Quality of Service (QoS) is the practice of using settings and techniques within a network and its equipment to control network traffic and limit the impact of network congestion.
Implementing QoS on a network is essential for organizations that use VoIP calling and other VoIP services. Increases in latency and packet loss can drastically affect the quality of those services. The issues users can experience with poor call quality related to QoS include distorted, choppy, delayed, or missing audio in the middle of an active call.
What is a QoS Problem?
Commonly reported symptoms related to QoS include the following:
- Choppy or robotic-sounding voices
- Garbled or distorted audio
- Delayed audio (latency)
- Brief periods of dropped or clipped audio
The audio quality issues listed above can occur because of the following reasons:
- Network is congested, causing dropped, delayed, or out of order packets
- Voice traffic is not being prioritized or dedicated bandwidth
- Applications/devices are oversubscribing bandwidth
✔ Properly configuring Quality of Service settings and implementing traffic shaping policies can help mitigate and prevent the issues listed above.
What is Not a QoS Problem?
The following call quality issues are not related to QoS:
- Phones not ringing (inbound calls fail to alert)
- Inability to make outbound calls
- Complete one-way or no-way audio from the start of the call
- Calls dropping immediately or failing to connect
The issues listed above can be caused by registration, firewall, NAT, and routing issues.
Note: If you are experiencing major issues with calls that do not relate to QoS, you may need to consider having the settings and policies on your firewall or router adjusted to make sure traffic and requests from the phones are not being blocked.
To review our recommended settings to adjust for routers and firewalls, reference the guide below:
Recommended Router and Firewall Settings
If you do not receive services or equipment from us, you can reach out to your IT team, Managed Service Provider (MSP), or Internet Service Provider (ISP) for further assistance.
If SpectrumVoIP provides your network equipment, our Technical Support team can help implement policies and settings for your internet network. If we provide or coordinate your internet services, our Technical Support team can manage the troubleshooting with your Internet Service Provider (ISP).
Check for QoS Issues
Since there are other factors in a network that can cause call quality issues, it is important to see is QoS is the root cause of a customer's audio quality issues.
If you suspect a customer is experiencing QoS issues, do the following to test further:
- Access to a PC connected to the same subnet as the phones.
- Start a test call to another user's phone or a cellphone.
- While the call is active, open a speed test website (e.g., www.speedtest.net or www.speed.cloudflare.com) in multiple browser tabs.
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Run the speed tests simultaneously to help simulate heavy bandwidth usage.
Note: While running a speed test, a healthy network should have the following metrics:
• Latency: Below 80 ms
• Jitter: 20 ms or less
• Packet Loss: 0% - During the call, listen for any call quality issues, such as choppy, delayed, or robotic audio.
- If there are noticeable call quality issues, end the speed tests and see if the audio quality returns to normal.
Note: If audio quality degrades noticeably during periods of heavy bandwidth usage but returns to normal afterward, you may need to consider having the QoS settings on your firewall or router adjusted to ensure voice traffic is prioritized during times of network congestion.
If you do not receive services or equipment from us, you can reach out to your IT team, Managed Service Provider (MSP), or Internet Service Provider (ISP) for further assistance.
If SpectrumVoIP provides your network equipment, our Technical Support team can help implement policies and settings for your internet network. If we provide or coordinate your internet services, our Technical Support team can manage the troubleshooting with your Internet Service Provider (ISP).