====== 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.

===== Why is determinism not a bandwidth question? =====

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.

===== How do the protocol families differ? =====

  * **[[technology:industrial-ethernet:profinet:start|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.
  * **[[technology:industrial-ethernet:ethercat:start|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.
  * **[[technology:industrial-ethernet:ethernet-powerlink:start|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.
  * **[[technology:industrial-ethernet:ethernet-ip:start|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.
  * **[[technology:industrial-ethernet:tsn:start|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.

^ Protocol ^ IEC 61158 type ^ IEC 61784-2 CPF ^ Determinism mechanism ^ Node hardware ^
| [[technology:industrial-ethernet:profinet:start|PROFINET IRT]] | Type 10 | CPF 3 | Hardware-reserved IRT phase; PTCP / IEEE 1588 sync | ASIC or FPGA required for IRT class C |
| [[technology:industrial-ethernet:ethercat:start|EtherCAT]] | Type 12 | CPF 12 | On-the-fly frame processing; one telegram per segment | ESC ASIC per node |
| [[technology:industrial-ethernet:ethernet-powerlink:start|POWERLINK]] | Type 13 | CPF 13 | Software-scheduled isochronous phase; managing node polling | Standard Ethernet NIC; no specialist silicon |
| [[technology:industrial-ethernet:ethernet-ip:start|EtherNet/IP]] | Type 2 | CPF 2 | CIP implicit messaging; determinism via network topology | Standard Ethernet adapter |

===== How should a buyer choose? =====

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.

===== Where does AEI's work sit? =====

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.

===== References =====

  * 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

===== Related =====

  * [[technology:start|Technology namespace]]
  * [[technology:fieldbus:start|Fieldbus]] — the installed base these networks connect to
  * [[technology:industry40:opcua:start|OPC UA]] — the layer above, for plant and MES data
  * [[https://aeicor.com/services/real-time-ethernet/|AEI Corporation — real-time Ethernet engineering services]]