EtherNet/IP I/O is routable
EtherNet/IP uses UDP/IP. I/O traffic crosses IP routers. PROFINET RT cannot.
10.2 EtherNet/IP
The previous chapter covered PROFINET, the dominant Industrial Ethernet protocol in Europe. In North America, the equivalent is EtherNet/IP. Both solve the same problem (real-time I/O over Ethernet) but take fundamentally different approaches to transport.
Why EtherNet/IP Exists
Section titled “Why EtherNet/IP Exists”Rockwell Automation needed an Industrial Ethernet protocol that worked with standard IP infrastructure. PROFINET RT bypasses IP, which means it cannot cross routers. EtherNet/IP uses standard TCP and UDP, making I/O traffic routable across IP networks. ODVA (Open DeviceNet Vendors Association) manages the specification. The IEC standardizes it as IEC 61158 Type 2.
CIP — Common Industrial Protocol
Section titled “CIP — Common Industrial Protocol”EtherNet/IP is built on CIP (Common Industrial Protocol), the same application layer used by DeviceNet and ControlNet. CIP defines the object model, services, and data types. EtherNet/IP transports CIP over standard TCP/IP and UDP/IP.
An EDS (Electronic Data Sheet) describes an EtherNet/IP device’s capabilities and parameters, similar to PROFINET’s GSDML.
Messaging Types
Section titled “Messaging Types”| Type | Transport | Use | Timing |
|---|---|---|---|
| Explicit messaging | TCP port 44818 | Configuration, diagnostics, parameters | Request-response |
| Implicit messaging (I/O) | UDP port 2222 | Cyclic real-time I/O data | Producer sends at fixed rate |
RPI (Requested Packet Interval) is the cycle time for implicit messaging. Typical values range from 2 to 10 ms. The producer sends data at the RPI rate without acknowledgment.
EtherNet/IP vs PROFINET
Section titled “EtherNet/IP vs PROFINET”| Feature | EtherNet/IP | PROFINET RT |
|---|---|---|
| I/O transport | UDP/IP | Ethernet Layer 2 |
| Routable | Yes | No |
| Cycle time | 2 to 10 ms | 1 to 10 ms |
| Standard body | ODVA | PI |
| Primary market | North America | Europe, Asia |
EtherNet/IP uses UDP/IP, so I/O traffic crosses IP routers. This is a significant advantage in large, multi-subnet installations. PROFINET RT achieves slightly lower cycle times by eliminating IP overhead.
Key Takeaways
Section titled “Key Takeaways”Dominant in North America
EtherNet/IP is the standard with Rockwell/Allen-Bradley PLCs. PROFINET is the standard with Siemens PLCs.
What Comes Next
Section titled “What Comes Next”Both PROFINET and EtherNet/IP provide fast I/O exchange, but neither guarantees zero packet loss during a failure. The next chapter covers HSR and PRP, the redundancy protocols that send every frame twice for zero-recovery-time failover in critical applications like IEC 61850 substations.
References
Section titled “References”- ODVA. (2022). EtherNet/IP Specification. ODVA Publication PUB00138.
- IEC 61158-6-2 — Industrial communication networks: Type 2 elements (EtherNet/IP)
- Rockwell Automation. (2021). EtherNet/IP Network Design and Planning Guide. Publication ENET-RM002.