What is Jitter?
Jitter is the variation in delay (Latency) of data packets while they are being transmitted across a network. In industrial networks and Real-time systems, jitter can lead to failures, intermittent communication or even process disruption.
In OT environments, jitter can have critical consequences, especially with deterministic protocols such as ProfiNET, EtherCAT or TSN.
🎯 Characteristics of Jitter
| Property | Explanation |
|---|---|
| Variable latency | Difference in time between the arrival of consecutive data packets |
| Measured in milliseconds | Usually expressed as standard deviation or maximum delay deviation |
| Unpredictable behaviour | Can be caused by congestion, buffering or interference |
| Critical for real-time | Disrupts time-critical communication, especially in motion control or audio/video |
🧠 Examples in an OT context
| Application | Impact of jitter |
|---|---|
| Motion Controller and servo motors | Irregular movements or vibrations in precision applications |
| PLC-to-PLC communication | Timing errors when synchronising machines |
| HMI visualisation | Delayed or inconsistent display of process data |
| TSN networks | Loss of deterministic guarantees when jitter is too high |
🔐 Causes and mitigation
| Cause | Mitigation |
|---|---|
| Non-deterministic switching | Use of industrial switches with QoS or TSN support |
| Bandwidth congestion | Network segmentation and reserving sufficient bandwidth |
| Buffering or queuing | Configure minimum buffering times on critical paths |
| Interference on wireless networks | Switch to wired connections or use WirelessHART |
🔁 Jitter vs. Latency vs. Packet Loss
| Term | Description |
|---|---|
| Latency | Total time a packet needs to travel from source to destination |
| Jitter | Variation in latency between consecutive packets |
| Packet Loss | Loss of packets in transit, often caused by excessive jitter or errors |
Although latency and jitter are related, jitter specifically concerns unpredictability, not delay itself.
📌 In summary
Jitter is the enemy of predictability. In OT networks where timing is crucial, jitter must be actively detected, limited and where possible eliminated.