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Introduction
Unlike unmanaged switches that simply forward Ethernet frames, managed industrial switches provide fine-grained control and monitoring capabilities to help engineers shape, prioritize, and protect traffic on control networks. Features like storm control, Quality of Service (QoS), VLANs, and redundancy protocols ensure that time-critical data gets where it needs to go—without being interrupted by less important traffic.
Let’s explore how these technologies work in a real-world automation context.
Storm Control: Preventing Network Floods from Disrupting PLC Communication
Industrial Ethernet networks often use broadcast and multicast traffic for device discovery, status updates, and protocols such as EtherNet/IP or PROFINET. However, if a device malfunctions or a loop forms between switches, broadcast storms can quickly saturate the network—causing latency, dropped packets, or even loss of PLC-to-I/O communication.
Storm control allows managed switches to set limits on broadcast, multicast, or unknown unicast traffic per port. When the threshold is exceeded, excess packets are dropped or rate-limited.
Example:
If a misconfigured vision system starts flooding the network with multicast frames, the managed switch’s storm control feature isolates the problem port and prevents the rest of the network—such as PLCs, drives, and HMIs—from losing connectivity.
This feature is essential for maintaining deterministic behavior in control networks, where even small delays can disrupt machine sequencing or process control loops
Quality of Service (QoS): Prioritizing Control and Safety Traffic
Industrial Ethernet carries many types of data simultaneously: control commands, status messages, configuration data, and even video streams. Not all packets are equally time-sensitive.
Quality of Service (QoS) lets engineers assign priority levels to traffic based on its importance. The switch can use IEEE 802.1p Class of Service (CoS) tags or DiffServ (DSCP) values to classify packets and manage queuing accordingly.
Example:
• High Priority: Real-time control data between PLCs and I/O modules (e.g., EtherNet/IP I/O messaging, PROFINET real-time).
• Medium Priority: HMI or SCADA communications.
• Low Priority: File transfers, firmware updates, or data logging to the cloud.
By ensuring that control traffic always has bandwidth preference, QoS reduces jitter and latency, helping automation systems meet real-time performance requirements.
VLANs: Segmenting the OT and IT Networks
In modern plants, operational technology (OT) networks often connect to enterprise IT systems for analytics and remote access. Without proper segmentation, broadcast domains can overlap, leading to congestion and security risks.
Virtual LANs (VLANs) let engineers logically separate traffic across the same physical infrastructure. Each VLAN acts as an isolated network, minimizing unnecessary traffic and protecting critical devices.
Example:
• VLAN 10: PLCs and field I/O for a packaging line
• VLAN 20: HMIs and engineering workstations
• VLAN 30: Remote monitoring and corporate data systems
This setup allows plant-floor devices to communicate only with approved endpoints, while preventing office or cloud traffic from interfering with production systems.
Redundancy and Link Aggregation: Ensuring Continuous Operation
Downtime in an industrial environment can cost thousands of dollars per minute. Managed switches support multiple redundancy methods to ensure continuous communication even if a cable or switch fails.
Common redundancy features include:
• Rapid Spanning Tree Protocol (RSTP): Automatically reconfigures the network path if a link fails.
• Media Redundancy Protocol (MRP): Provides fast ring recovery (typically <200 ms) for PROFINET networks.
• Link Aggregation (LACP): Combines multiple physical connections into one logical link for higher bandwidth and failover.
Example:
A bottling line network uses an MRP ring topology connecting PLCs, HMIs, and drives. If one segment of the ring is damaged, the network automatically reroutes traffic in the opposite direction, keeping operations running without interruption.
Monitoring and Diagnostics: Visibility for Predictive Maintenance
Managed switches provide SNMP, port mirroring, and web-based diagnostics that give engineers insight into network health. This visibility enables proactive maintenance and faster troubleshooting.
Example:
An engineer can use the switch’s web interface or an industrial network management tool to view port utilization, link errors, or packet loss trends. Early detection of rising error counts on a port could indicate a failing cable or electrical interference—allowing repairs before communication is lost.
Some industrial switches also support Syslog, event notifications, and network topology mapping, making it easier to integrate with plant monitoring systems.
Conclusion
In industrial automation, uptime, reliability, and determinism are non-negotiable. Managed industrial switches are key to achieving these goals by offering control over how traffic flows across the network.
Through storm control, QoS, VLAN segmentation, and redundancy protocols, engineers can design Ethernet networks that are not only fast—but also predictable, secure, and resilient under real-world conditions.
As factories evolve toward Industry 4.0 and IIoT architectures, deploying managed switches ensures that your automation network can support both legacy control systems and the data-intensive applications of the future.
Learn more with Maple Systems
Whether building complex industrial networks or setting up your first network switch, Maple Systems has an expansive library of technical and educational resources to support your success. Explore our support pages for tutorials, technical notes, and sample projects on a variety of topics.
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