Whilst redundancy is a valuable tool to bolster network resiliency, it is essential to recognise that it introduces a trade-off that involves potential interruptions in communications. By carefully assessing a network’s recovery time and understanding the PLC communication expectations, network operators can strike a balance that ensures both resiliency and consistent, uninterrupted industrial communications.

In the realm of industrial networks, there is a primary focus on mission-critical devices, such as Programmable Logic Controllers (PLCs), which play a pivotal role in orchestrating key decisions. PLCs are responsible for transmitting essential messages to other PLCs, remote I/O devices, or SCADA software. These devices typically operate in a cyclical process, ensuring that messages are sent reliably within specific timing windows. The frequency of these messages, as well as the tolerance for missed responses, varies depending on PLC programming, the vendor, and the communication protocol used.

The critical aspect to consider is how redundancy mechanisms come into play and their potential impact on an industrial network. Redundancy mechanisms are designed to ensure that network faults are addressed swiftly, however, this comes at the cost of potentially experiencing more frequent outages. When a network fault is detected, recovery procedures are initiated. This means that network traffic may experience interruptions for short periods. The time it takes for the network to recover and for traffic to resume its end-to-end flow is determined by various factors, including the specific communication protocol, vendor implementations, and configuration settings.

To assess the potential impact of redundancy on an industrial control system, it’s crucial to consider the following factors:

  • Recovery time – The time it takes for the network to recover after a fault occurs is a critical parameter. Understanding this recovery time is essential to evaluate how it aligns with the timing requirements of its PLCs.
  • PLC communication expectations – Each PLC has specific expectations regarding the frequency and timing of message exchanges. It is essential to understand how often a PLC expects a response and within what time frame.

By defining the recovery time and comparing it to critical PLC communication requirements, network operators can determine whether redundancy-induced outages will lead to interruptions in their communications. This assessment helps them make informed decisions about redundancy strategies in their industrial network.

This sponsored editorial is brought to you by IPD. For more information on IPD’s Industrial Communications range, visit

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