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QoS (quality of service) Definition, benefits and how to use it

Kirsty Moreland
Last Updated May 20, 2024 9:52 pm

 

Your humble internet connection has a lot of jobs to do at once. In this article, we’ll talk about QoS, and how lets you tailor your network settings to suit your needs.

You might think you’re just browsing, but the chances are your internet connection is servicing multiple other applications simultaneously. In fact, the average person has around 80 apps installed on their device.

From messaging apps and VoIP software, to downloads and geolocation, all of those apps are using some bandwidth. But some are more important than others.

What is QoS (quality of service)?

Quality of Service (QoS) refers to the use of digital tools and settings to ensure your most important network traffic is prioritized. It guarantees the performance of inelastic applications like VoIP calls, even when bandwidth is shared with multiple programs.

How does QoS work?

The objective of quality of service settings is to proactively manage traffic on your network. This helps to prevent jitter in gaming, calls and streaming.

Any time you use the internet, your device is sending and receiving packets of data over the network. For real-time applications such as VoIP calls, streaming and games, it’s critical that the network transmits these packets smoothly. 

But this isn’t always the case. Networks generally have multiple apps running simultaneously, but limited bandwidth to manage all those streams of traffic. With different traffic streams jostling for priority, real-time applications like games and VoIP calls can suffer freezing, glitching and distortion, also known as jitter.

To understand how QoS overcomes these issues, let’s take a closer look at network traffic.

Network traffic characteristics

QoS makes decisions on how to prioritize traffic on a network. It does this based on three key characteristics that affect data transmission:

  1. Bandwidth
  2. Packet loss
  3. Latency

Bandwidth

Bandwidth is a measure of connection speed in bits per second (BpS). Since every network has limited bandwidth, QOS instructs the network on how this resource should be assigned. 

Generally, bandwidth is managed on a first come first serve basis, with the network transmitting data packets in whichever order they arrive. With QOS, you can create different “queues” with different types of traffic, ensuring the most important queue receives most bandwidth. In this way, you can prioritize voice or video packets over less sensitive text packets.

Packet loss

Packet loss describes the percentage of data packets lost in transmission over a system, normally due to congestion.

Using QoS enables you to prioritize which packets are dropped. This allows data relating to critical applications to be preserved, preventing interference to those programs.

Latency

Latency is a measure of the time it takes for a signal to travel across a network and back again. Also known as RTT (round trip time), delay is measured in milliseconds.

Delayed packets can distort a call, game or streamed content, making it a significant factor in connection quality. Latency in gaming, for example, can mean the difference between winning and losing a tournament.

There are various different types of delay, some that can be controlled and some that cannot.

  • Processing delay

This is the time it takes for a system to treat information before it is sent across the network. It includes tasks such as router look-up and ARP table checking, the speed of which can be affected by the processing power of your hardware.

  • Queuing delay

This is the length of time a packet has to wait in a queue before it is transmitted, and will be affected by network congestion.

  • Serialization delay

This is the time it takes for the bits in a frame to be sent to the physical interface to be displayed to the user.

  • Propagation delay

The length of time it takes for bits to pass across a physical medium of transmission, such as fibre optic cable or satellites.

Using QoS allows you to proactively manage certain types of delay. For example, you can minimize queuing delay for critical applications by creating different queues of packets. This would allow the most important ones, such as voice packets, to be prioritized.

QoS tools

As you know, different network applications have different requirements, with voice and video applications being the most demanding. The job of quality of service tools is to sort through all these different applications, understanding their function and needs, and prioritizing accordingly.

Let’s take a closer look at the tools we use to implement QoS.

Classification and marking

Classification in QoS involves examining network traffic and categorizing it into different classes based on certain criteria, like source or type of service. Marking then tags these classified packets with specific labels to ensure they receive appropriate handling throughout their journey in the network, facilitating priority management and ensuring resources are allocated efficiently for optimal service quality.

Queuing

Queueing in Quality of Service (QoS) refers to the process of managing how packets are buffered when they cannot be transmitted immediately. It prioritizes different types of traffic to ensure that more urgent or important data packets are sent first, while less critical packets wait in line. This helps in managing congestion and maintaining the quality of service for high-priority network traffic, ensuring efficient use of available bandwidth and improving overall network performance.

Shaping and policing

These QoS mechanisms help to regulate network traffic.

Shaping smooths out traffic flows to conform to a specified rate, delaying excess packets to prevent congestion. Policing, on the other hand, limits the volume of traffic to a predefined rate, potentially dropping packets that exceed the limit to enforce compliance with network policies. Both methods aim to ensure network resources are used efficiently and high-priority traffic is not negatively affected by congestion.

Congestion avoidance

Congestion avoidance in QoS refers to techniques that monitor network traffic load to prevent congestion before it becomes problematic. This proactive approach adjusts the rate of packet transmission based on the current state of the network to avoid overwhelming it. By doing so, it helps maintain high-quality network performance and ensures that critical data packets are delivered efficiently without delay or loss.

How to implement QoS settings

You’re probably wondering how to activate QoS on your own network. Implementing quality of service settings typically involves several steps. 

Identify your traffic streams

Begin by identifying the types of traffic present on your network. This involves analyzing packet data to distinguish between various services and applications.

This can be done through deep packet inspection (DPI), examining port numbers, or checking IP addresses against known service ranges. Network monitoring tools and traffic analyzers are typically used to automate this process, providing insights into the composition of network traffic, which can then be managed or prioritized according to organizational policies or QoS settings.

Determine priority traffic

With a clear list of all the different applications using your network, you can start to decide which ones should be prioritised. Generally speaking, real-time applications like VoIP apps, video calls, streaming and gaming platforms should be your priority. Apps that are not real-time, such as mapping or social media apps, can be deprioritized, since latency has less of an impact.

Configure network devices

Once your priorities are clear, you’ll configure your routers and switches to recognize and prioritize traffic correctly.

You can typically access your router’s settings through a web interface. From here, navigate to the Quality of Service (QoS) section. You will be able to specify rules or policies that prioritize traffic based on criteria like application, device, or port number.

You can set priority levels for different types of traffic, such as giving higher priority to VoIP or gaming. The exact steps can vary depending on the router model, so consulting the user manual or the manufacturer’s website for instructions specific to your device is recommended.

Monitor network performance

You can track the performance of your network using monitoring tools. These track and analyze QoS metrics like bandwidth usage, packet loss, jitter, and latency, and often offer dashboards and alerts to help you monitor whether QoS policies are effectively prioritizing critical traffic. Regular monitoring allows for adjustments to QoS settings to improve network performance and ensure compliance with service level agreements (SLAs).

Quality of service tailors your network to your needs

It should be obvious by now that using QoS settings is a sensible move for anyone who uses the internet. Knowing how these settings work, and how to implement them, enables you to tailor your connection for the applications you actually use. This means a better network performance, and a better user experience for you.