Quality of Service (QoS) for VoIP phone systems

Modified on Mon, 13 Apr at 9:44 AM

Quality of Service (QoS) for VoIP Phone Systems

Ensuring top-notch call quality is crucial for your business communications. This guide explains how Quality of Service (QoS) settings work in VoIP systems, helping you optimise your network for clear, reliable conversations.

What is QoS?

Quality of Service (QoS) is a feature of broadband routers and switches used to manage data traffic across your network so that more important traffic passes through first. It is designed to reduce interference such as packet loss, jitter, and latency, resulting in a performance improvement for critical network traffic.

Why do I need to enable QoS for my VoIP system?

QoS can prioritise voice and VoIP traffic to ensure calls are not affected by network congestion. It also protects voice traffic from network utilisation spikes caused by software distributions, video streaming, and other high-bandwidth applications.

Please note: This does not apply to third-party routers — only bOnline purchased routers. Third-party routers may not be checked, and you (the owner) may need to contact your Internet Service Provider.

How to set up QoS on the Zyxel VMG1312-T20B

Navigate to Network Settings and click QoS.
Enable QoS.
Select Upstream Traffic Priority Assigned by.
Select Ethernet Priority from the options available.
Reboot your router to apply the settings.

How to set up QoS on the Zyxel VMG1312-B10D

Navigate to Network Settings and click QoS.
Enable QoS.
Select Upstream Traffic Priority Assigned by.
Select Ethernet Priority from the options available.
Reboot your router to apply the settings.

Understanding QoS Upstream Traffic options

When setting up QoS, you will have four options for how upstream traffic priority is assigned:

None: Disables auto priority mapping and places packets into queues according to your classification rules. Traffic that does not match any classification rule is mapped to the default queue with the lowest priority. This is the default setting and is not recommended.
Ethernet Priority: Automatically assigns priority based on the IEEE 802.1p priority level. This is the recommended option for VoIP.
IP Precedence: Automatically assigns priority based on the first three bits of the TOS field in the IP header.
Packet Length: Automatically assigns priority based on packet size. Smaller packets receive higher priority, as control, signalling, VoIP, and real-time packets are usually small. Larger packets are typically best-effort data such as file transfers.