How Do You Implement QoS (Quality of Service) in Industrial Ethernet?

Networks do periodically become congested, but data integrity and mission-critical applications still need to be protected. QoS guarantees them consistent and available network resources, by prioritising certain data packets and sending them ahead of other, less critical traffic. The network administrator stores this other traffic using the QoS priority queuing mechanism until sufficient bandwidth becomes available to send it. 

Why is QoS Important?

All computer networks experience periodic congestion, regardless of their size. This happens when more traffic is coming into a router or Ethernet switch than it can send out. This can potentially result in connectivity issues such as latency or packet loss. It can be caused by things like a backup in progress, which temporarily saturates the links. You’ll also experience high network traffic at predictable times in your working day, when everyone’s simultaneously running the same application.

If there’s insufficient bandwidth on an industrial network for all traffic, you’ll experience latency, so that communicating this critical information will lag behind. Latency of even a few milliseconds’ duration can result in extremely costly issues, from malfunctioning equipment to expensive downtime. QoS puts critical data streams first in industrial network traffic, preventing the risks of latency and dropped packets.

You’ll find QoS equally advantageous for business applications like video conferencing, video surveillance network data, VoIP and online training. These apps require minimum bandwidth and have high sensitivity to jitter, with minimum and maximum latency limits. QoS ensures the best user experience with these apps by prioritising the relevant data packets and bandwidth allocation. 

QoS Configuration

QoS configuration for industrial switches can be highly complex, and you might need professional help in aspects like choosing a QoS model. However, you can take some steps to ensure that it’s correctly set up:

1. Identify Critical Apps

First of all, you need to assess your network to identify the highest priority applications and those that may suffer when the network is congested. These will include industrial control systems with high and heavy bandwidth requirements, VoIP and video streaming. To get the best results, not only network administrators but all business department leaders should participate in determining top priorities.

2. Configure Classes 

Next, you need to allocate and configure apps into different classes of traffic on the network switch. This means sorting them into groups of data packets that require similar treatment because they share similar characteristics. Some examples of classes include VoIP voice traffic, audio and video content traffic, and a separate class for everything else. 

Typical strategies for configuring classes divide them into four, eight or 12 groups. You don’t want too many classes on one network, and you don’t need to create separate classes for every single type of traffic. The fewer QoS traffic classes you configure, the easier you’ll find it to deploy and maintain them.

3. Assign Priorities

Once you’ve created your traffic classes, you need to assign them priorities, so the Ethernet switch knows what to do. When networks get congested, the QoS reads the information supplied on each packet header. If it reads a priority command, this guarantees a minimum or maximum bandwidth allocation. Less urgent packets are queued up internally and stored until the network has the processing capacity for them.

4. Set Bandwidth Limits

It’s vital to set bandwidth limits for all classes of traffic on the network, so that the available bandwidth isn’t all gobbled up by high-priority traffic. Each class should have a base (guaranteed) bandwidth assigned to it, as well as a maximum, which ensures enough usable bandwidth is left over after priority traffic for the other classes. 

Implementing QoS in your Industrial Ethernet Network

Network congestion on a large scale isn’t just annoying but threatens your productivity and profits. Multiple networked systems in a distributed industrial plant must work collaboratively with automated devices in perfectly synchronised sequences. They’ll be communicating constantly to provide real-time information on your system’s operational status, timing controls or maintenance needs, so prioritising tasks is crucial. 

Implementing QoS is not a cut-and-dried operation, but an ongoing process that demands regular monitoring and oversight. After you’ve configured it, it’s important to ensure optimal network performance by running network tests and fine-tuning its settings. If you follow these procedures, you should be able to configure and implement QoS on your industrial Ethernet switches to satisfy your specific automation needs.