VMware Cloud Foundation (VCF) 9 introduces the Industrial vSwitch (IvS), a networking solution specifically designed to meet the demands of industrial automation. While traditional virtual switches like vDS are built for general workloads, IvS focuses on low latency, minimal jitter, and true Layer 2 behavior as required by protocols such as PROFINET. This article explains why IvS is necessary, how virtual PLCs (vPLCs) are integrated within it, and the role PROFINET plays in this setup.
What Is a PLC and Why Is Timing Critical?
A programmable logic controller (PLC) is a robust computer that reads inputs from sensors, executes a control program, and writes outputs to actuators. This cycle—often referred to as the scan cycle—repeats at fixed intervals, frequently just a few milliseconds. In a welding cell, for example, a sensor detects the arrival of a car body, the PLC stops the conveyor belt, engages clamping devices, and issues a start command to the welding robots. If the input signal arrives too late, the PLC operates on outdated data; if the output signal is delayed, the machinery responds too slowly. Both scenarios can cause the cell to enter a safe state, halting production. Therefore, not only the average latency matters, but also the worst-case delay (maxLatency) and jitter—the variation in delay from frame to frame.
Virtual PLCs (vPLCs) and Their Challenges
A vPLC is simply PLC software running as a virtual machine on an ESXi host. The control algorithm remains unchanged; only the execution environment shifts from dedicated PLC hardware to a shared server. Virtualization offers benefits such as faster recovery from failures, centralized management, consistent software stacks, and higher consolidation rates (up to twelve vPLCs per host). However, it also introduces new challenges: The vPLC must maintain its control cycles reliably despite sharing CPU time with other VMs. To address this, the Latency Sensitivity flag is set to High, allowing the ESXi scheduler to prioritize the vPLC. The network must also operate deterministically—each switch, NIC, and uplink can contribute to both latency and jitter. A standard vDS cannot provide these guarantees, as it is optimized for best-effort traffic and lacks mechanisms to enforce latency ceilings.
How PROFINET Works and Why IvS Is Needed
PROFINET is an industrial Ethernet protocol built on the Ethernet layer (Layer 2) but defines its own mechanisms for real-time communication. It differentiates between:
- Standard TCP/IP traffic for configuration, diagnostics, and parameterization—time-insensitive.
- PROFINET RT (Real Time) for cyclic process data. RT frames use EtherType 0x8892, bypass the standard TCP/IP stack, and are sent directly over Ethernet. This requires the sender and receiver to be in the same broadcast domain; routing is not possible.
- PROFINET IRT (Isochronous Real Time) for highly demanding motion control applications with sub-millisecond cycles and strict synchronization. IRT requires time-aware shapers and clock synchronization at every hop—something that IvS does not currently support.
For most factory automation scenarios, PROFINET RT is sufficient. To allow a vPLC to communicate with physical I/O modules, drives, or robots, its virtual network interface must offer a reliable, latency-bounded Layer 2 segment. This is exactly what the Industrial vSwitch provides: It assigns each vPLC a dedicated VLAN segment that extends through the physical switch to the field device expansion. Within this segment, PROFINET RT frames are forwarded with low, consistent latency, while other traffic (e.g., management traffic) can be routed via standard NSX components.
Summary
The Industrial vSwitch in VCF 9 bridges the gap between the virtualized data center environment and the hard real-time requirements of industrial automation. By combining latency sensitivity settings for vPLCs, dedicated VLAN segments, and a switch that forwards Layer 2 PROFINET RT frames with bounded jitter, it delivers a platform where control software running as a virtual machine performs as reliably as dedicated PLC hardware. For applications requiring IRT, coordination with the PLC vendor and validation of IvS capabilities remain necessary, since current IvS implementations do not yet support IRT.
References
https://vconfig.pl/2026/10/06/industrial-vswitch-in-vcf-9-introduction-to-ivs-vplcs-and-profinet/