EtherNet/IP

EtherNet/IP (Ethernet Industrial Protocol) is an open communications protocol developed by Rockwell Automation, managed by ODVA and designed for use in process control and other industrial automation applications. EtherNet/IP can be easily confused as a combination of Ethernet (the physical layer, link, or medium used in most office and many industrial networking environments) and the Internet Protocol, the world’s most ubiquitous (internet) networking protocol and part of the TCP/IP model, comprising a suite of protocols operating at the link, internet (or networking), transport, and application layers.

By comparison, EtherNet/IP is an industrial application layer protocol operating over the Ethernet medium and used for communication between industrial control systems and their components, such as a programmable automation controller, programmable logic controller or an I/O system. Furthermore, the “IP” in EtherNet/IP, is not an abbreviation for “Internet Protocol” but instead stands for “Industrial Protocol”, referring to Rockwell’s adoption of Common Industrial Protocol (CIP) standards as EtherNet/IP was developed.

Confusing matters further is the fact that when using the OSI Reference Model, EtherNet/IP, at the application layer, operates over both Ethernet (at the physical layer) and IP (at the network layer) and thus complements each of these technologies.

History

EtherNet/IP was developed in the late 1990’s by Rockwell Automation as part of Rockwell’s industrial Ethernet networking solutions. With little or no input taken from other ODVA members, Rockwell gave EtherNet/IP its moniker and handed it over to ODVA, which now manages the protocol and assures multivendor system interoperability by requiring adherence to established standards whenever new products that utilize the protocol are developed.

Today, EtherNet/IP is most commonly used in industrial automation settings (e.g., water processing plants, manufacturing facilities, utilities) in the US and Asia for communication to and from Rockwell Automation’s Allen-Bradley-brand control systems. However, other industrial automation and control system vendors, including Opto 22 and WAGO Corporation, have developed programmable automation controllers and I/O capable of communicating via EtherNet/IP.

Technical Details

EtherNet/IP classifies Ethernet nodes as predefined device types with specific behaviors. Among other things, this enables:

• • Transfer of basic I/O data via UDP-based implicit messaging
  • Uploading and downloading of parameters, setpoints, programs and recipes via TCP (i.e., explicit messaging.)
  • Polled, cyclic and change-of-state monitoring via UDP, such as RPI and COS in Allen Bradley's ControlLogix control systems.
  • One-to-one (unicast), one-to-many (multicast), and one-to-all (broadcast) communication via TCP.

The EtherNet/IP application layer protocol is based on the Common Industrial Protocol (CIP) standard used in both DeviceNet, CompoNet and ControlNet.

As EtherNet/IP is now an open technology, it was suggested to publish the Level 2 source codes via www.sourceforge.net. However, in lieu of this, freeware source code can now be downloaded from ODVA's website at [1].