What is Read Rate in Operational Technology?
Falling under the umbrella of “data polling” attributes, “BACnet excessive read rate” is the frequency at which a device on your network is requesting data from another device as part of data acquisition management processes in OT systems. Read rate is a key metric in managing building control systems.
In the case of, say, a temperature sensor, the read rate would be how often a device or software is polling that sensor to provide an updated measurement.
What Makes It Excessive in Building Control Systems?
While polling and reads are normal functions of your system, it’s not uncommon to have these requests become overwhelming. Think of our temperature sensor above. If that device is being constantly polled for updates, it’s generating data on the network, consuming CPU cycles, and potentially affecting the performance of industrial equipment it networks with. Now assume you have hundreds of similar sensors all generating a constant stream of data across a network with limited bandwidth. The traffic adds up fast.
Excessive rates can negatively affect the performance of your network, leading to an increase in response times, decreased resources, and instabilities across your system. Additionally, excessive read rates can disrupt industrial and manufacturing processes and lead to inefficiencies.
In OptigoVN, Excessive Read Rate warnings are displayed in the expanded list under Rate and Frequency of Object Reads, Writes, and COVs>Excessive Read Rate. Our diagnostic threshold returns a warning when a read property request for the same point occurs more than once within five minutes.
Not all High Read Rates are “Excessive” in Industrial Control Systems
It’s important to note that high read rates in OT systems aren’t always a bad thing. There are certainly situations where precise data is a requirement. Back to our temperature sensor example. If that sensor is located in a highly sensitive area, like a data center where temperatures can rise 3.5 degrees for every minute the cooling system is offline, you may want frequent readings to maintain a very precise temperature. High read rates are sometimes required for effective supervisory control in critical environments, such as industrial control systems (ICS) where maintaining operational technology is crucial. But a sensor monitoring the temperature outside the building? Those readings aren’t going to fluctuate often, so constantly polling for updates won’t provide more value.
In our experience, excessive read rates are often the result of programmers creating blanket polling policies for all object types across all devices connected. In a large system, this has the potential to trigger a flood of unnecessary data traffic.
How To Fix Excessive Read Rates in OT Networks
In this case, the “fix” is a simple matter of securing OT systems to prevent unauthorized access and tuning the frequency of read rates to help optimize your overall network performance. OptigoVN’s Site Scopes can help you dig into your diagnostic test results to identify the culprit devices that are at risk of triggering a failed diagnostic result by exceeding our threshold.
We’ve also created a handy cheat sheet of Object reference descriptions to help you understand what value is being read.
With this information, you can now tune your devices to a more appropriate polling rate if needed. Some common ways to consider tuning include:
Configuration Review: Review and verify configuration settings for data polling rates to ensure they align with the intended requirements.
Reduce Poll Rates: Set appropriate polling frequencies based on the importance of the data, the rate of change, and the system’s operational needs.
Optimize Control Programming: Optimize control programs and scripts to avoid unnecessary or redundant data polling.
Convert Reads into Change-of-Value: Instead of polling the value, use a Change-of-Value “push” notification when the value changes.
Continuous Network Monitoring: Monitor network traffic and resource usage to identify patterns of excessive read rates.
Don’t Forget to Check Your Work!
Once you’ve completed your tuning, we recommend OptigoVN users upload new PCAP files (or set up continuous monitoring with our BACnet Capture Tool) to confirm improvements to your network health. Network administrators play a crucial role in verifying and maintaining the health and security of OT networks.
Simply click back into the “Excessive Read Rate” results, search for a destination device, and confirm that the average gap between reads has increased, or disappeared, which means the average gap is now >300s.
Ready to help quiet the noise and bottlenecks BACnet excessive read rate can cause across your OT networks? OptigoVN offers free monitoring and diagnostic tools for your BAS and OT networks. Sign up for free today.
