Industrial real-time Ethernet

Industrial real-time Ethernet is a family of protocols that run control traffic over standard Ethernet hardware while bounding when each frame arrives, not just whether it arrives. PROFINET, EtherCAT, POWERLINK and EtherNet/IP each solve that timing problem differently. TSN is the IEEE layer that lets them share one wire with everything else. AEI Corporation works at the level where those differences matter: protocol stack integration, driver and PHY bring-up, cycle-time budgeting, and pre-compliance testing before a device goes to a certification lab.

Determinism is a question of variance, not throughput. A gigabit link with an unbounded worst case is useless to a control loop; a 100 Mbit/s link with a guaranteed transmission slot is not. Standard switched Ethernet is non-deterministic because queuing delay depends on what else is in the queue. Add traffic and the tail of the latency distribution moves, even when average link utilisation is low.

Every protocol on this page is an answer to that one problem, and they answer it in one of three ways: schedule the medium (reserve a phase or a time slot so control frames never contend), change what a frame is (one frame serving many nodes instead of one frame per node), or police the traffic (admission control and per-stream shaping in the switch). Which answer suits a machine depends far more on its topology and node count than on its data rate.

• PROFINET (IEC 61158 Type 10, profile CPF 3 in IEC 61784-2) — one protocol with graded real-time classes. RT is prioritised traffic on standard switches; IRT (conformance class C) reserves a transmission phase in hardware for clock-synchronous motion. The class distinction is the whole engineering decision.
• EtherCAT (IEC 61158 Type 12, CPF 12) — processing on the fly: one frame passes through every node, each slave reading and writing its own data as the frame transits. Efficiency scales with node count in a way frame-per-node protocols do not.
• POWERLINK (IEC 61158 Type 13, CPF 13) — a software-scheduled slot mechanism on unmodified Ethernet hardware, with a managing node polling controlled nodes in an isochronous phase.
• EtherNet/IP (IEC 61158 Type 2, CPF 2) — CIP over standard TCP/UDP Ethernet; the CIP object model is the interoperability surface, and determinism comes from the network design around it.
• TSN — not a protocol but a set of IEEE 802.1 amendments to the bridge itself: 802.1AS (gPTP time sync), the 802.1Qbv time-aware shaper and 802.1Qbu frame preemption with IEEE 802.3br (both amendments folded into IEEE 802.1Q-2018 and later editions), 802.1CB frame replication and elimination, 802.1Qcc configuration. It is the convergence layer the protocols above are migrating onto, not a replacement for them.

Start from the constraint that actually binds. Axis count and cycle budget point toward EtherCAT or IRT-class PROFINET. Ecosystem and end-customer mandate frequently decide it before engineering does. A machine sold into a plant standardised on one protocol will speak that protocol. Certification cost and time is the third factor and the most often under-planned: the conformance path, not the stack, is usually what sets the schedule.

The honest answer for most device makers is that the protocol is chosen for them; the real question, covered in the child pages above, is what implementing it well costs.

We integrate and port protocol stacks onto customer hardware, do the driver and PHY-level work underneath them, budget cycle times against real topologies before hardware is committed, and run pre-compliance testing so a device arrives at an accredited test lab already passing. Where a design is being taken onto a converged network, we do the TSN configuration and verification work alongside it.

• IEC 61158 (industrial communication networks — fieldbus specifications) — the type-numbered protocol specifications referenced above
• IEC 61784-2 (communication profiles for real-time Ethernet) — the CPF profile numbers referenced above
• IEEE 802.1Q-2018 and later editions — bridging base standard, incorporating the Qbv and Qbu TSN amendments
• IEEE 802.1AS — timing and synchronisation (gPTP) for time-sensitive applications
• IEEE 802.3br — interspersing express traffic (frame preemption at the MAC)
• IEC/IEEE 60802:2026 (Time-Sensitive Networking Profile for Industrial Automation) — published June 2026; defines the TSN profiles, features, configurations, protocols, and YANG modules for converged industrial automation networks

• Technology namespace
• Fieldbus — the installed base these networks connect to
• OPC UA — the layer above, for plant and MES data
• AEI Corporation — real-time Ethernet engineering services