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What is EtherNet/IP Protocol?

EtherNet/IP is an industrial Ethernet protocol. It combines traditional Ethernet with an industrial application layer protocol, which is called Control and Information Protocol (CIP).

EthernetIP Protocol

EtherNet/IP is a communication protocol mostly associated with Rockwell Automation for use in industrial factories. EtherNet/IP offers reliable communication and reduced system complexity, which has led to its wide adoption. It is managed by ODVA (Open DeviceNet Vendors Association) and is the current standard for industrial communication.

Table of Contents

History EtherNet/IP

In the 90s a group from ControlNet International Ltd. got together and created what we know as EtherNet/IP today.

In 2000 the Open DeviceNet Vendors Association – ODVA agreed to participate in the development of EtherNet/IP.

In 2009, all the responsibilities of the project moved to ODVA.

EtherNet/IP Today

Today, EtherNet/IP is the most widely used protocol in Industrial Ethernet. Its connectivity extends to more than 169 countries and represents more than 20,000 users. EtherNet/IP is one of the most successful open standards for industrial Ethernet in the world.

It provides an opportunity for companies to develop integrated control systems that are easily expanded while remaining interoperable with other vendors’ products. One reason for this is that EtherNet/IP was designed to operate over a variety of physical media and topologies.

What is Ethernet/IP?

EtherNet/IP is an application layer protocol, which means it’s simply a way of organizing data inside a TCP/IP packet.

The data on EtherNet/IP network is represented as values called attributes when grouped together to create objects. The EtherNet/IP Specification defines those objects.

There are EtherNet/IP Application Objects that have the data for your specific device. For example, an EtherNet/IP RemoteIO device has a specific Object.

Messages transferred from EtherNet/IP Scanner to Adapter are from two types: Explicit Messages and I/O Messages (continuously transferred).

CIP (Common Industrial Protocol) is part of EtherNet/IP. CIP defines the Object structure and specifies the message transfer. CIP protocol over Ethernet is EtherNet/IP.

How EtherNet/IP Works

To explain how EtherNet/IP works, we have to talk first about the OSI model (Open Systems Interconnection Reference Model ) which specifies the different layers of a communication network.

The OSI Model is built from seven layers: 

  • Application: The application layer is exposed to the end-user like web browsers or applications.
  • Presentation: The Presentation layer prepares the translation of the application data and format into network format (encryption/decryption of data for secure transmission). 
  • Session: A session occurs between two devices. This layer connects the application to the network.  
  • Transport: layer is also called the Transmission Control Protocol or TCP. The TCP is built on top of the Network layer (IP).
  • Network: The network layer (IP) is where packet forwarding (routing), setup and creation of connections occur.
  • Data Link: The data link layer is responsible for data transfer.  
  • Physical: The Physical layer is where physical components connect. This includes the cables, sufficient voltages and frequencies.  

Note that Ethernet is at the data link layer and physical layer stage since it’s the actual physical connection.

The physical layer supports wireless, copper cables, fiber .etc. The data link layer supports few standards, depending on the physical layer – IEEE 802.3 (fiber), IEEE 802.3 or 802.1 (copper), and IEEE 802.11 (WiFi).

EtherNet/IP goes through three layered protocols: 

  • CIP 
  • TCP/IP And UDP
  • IP 

EtherNet/IP will progress from CIP layers to the TCP/IP layer, and then to the IP layer.

What are the EtherNet/IP topologies?

EtherNet/IP is an active infrastructure, with network segments using point-to-point connections in a star topology. The key to this topology is linking layer-2 and layer-3 switches.

The EtherNet/IP network also supports linear and single fault-tolerant ring topology. For that, it uses embedded switches and Device Level Ring (DLR) technology.

These topologies can combine to form a mesh topology to optimize the overall communication layout.

Benefits of EtherNet/IP

Because ControlNet, DeviceNet and EtherNet/IP use a common application layer protocol, they also share an object library and device profiles. These objects allow for plug-and-play connectivity for complex devices from different vendors. The object definitions are rigorous and support real-time I/O messaging, configuration and diagnostics over the same network.

This means that users can connect to complex devices like drives, robot controllers, bar code readers, and weigh scales without custom software. The result is faster start-ups and superior diagnostics.

In addition, EtherNet/IP provides users with both explicit (information) and implicit (control) messaging services. EtherNet/IP, as a result, supplies every service that is essential in control and device-level networks – from polled, cyclic, and change-of-state trigger mechanisms to point-to-point and multicast data transfer.

Given the rapid adoption of EtherNet/IP, vendors from across the globe have already developed thousands of products. This is important if only to illustrate that support for EtherNet/IP is unparalleled and will only continue to grow.

Summary of benefits:

  1. Established – EtherNet/IP supported by leading networks organizations: ODVA – Open DeviceNet Vendor Association, CI – ControlNet International, IAONA – Industrial Automation Open Network Alliance and IEA – Industrial Ethernet Organization
  2. Compatibility – Ethernet/IP uses the same tools and technologies as traditional Ethernet. The TCP protocol, the IP Protocol, the cables and media and signaling technologies. For example, the physical layer and data link layer are based on the IEEE 802.3 Ethernet standard.
  3. Support – Since Ethernet/IP is the go-to standard technology platform guarantees that it will move forward as the traditional technologies grow in the future. Also, there are a lot of tools, training and vendors willing to help.
  4. Standard – Ethernet/IP is a certifiable standard. The organizations supporting Ethernet/IP will ensure a consistent standard through certified test labs.
  5. Open – Ethernet/IP technology is also completely free for developers & vendors
  6. Universal – Today, Most enterprises use EtherNet/IP, hundreds of vendors support the CIP protocol.

An Overview of CIP

The Common Industrial Protocol (CIP) transferring automation data between devices. In the CIP Protocol, every device identifies itself with a set of objects. Each object contains related data values of the device.

Every device contains the Identity object available to other devices. The identity object contains values termed attributes. Attributes for the identity object hold the vendor ID, device serial number, date of manufacture and additional identity data.

CIP will not define how the object data is performed, only which values or attributes must be supported.

The CIP Objects

  • Required Objects – Required objects are present for every CIP device. These objects are the Identity object, a Network object and a message Router object.
  • Application Objects – Application objects are specific to the device type and function. For example, a Motor object on a Drive System has attributes for the frequency, current, etc.
  • Vendor-Specific Objects – The vendors include these objects as extra features of the device.

Messaging Protocol

The connections in a CIP network can be classified into explicit messaging connections and implicit (I/O connections) messaging.

  • Explicit messaging connections are generic, multi-purpose communication between devices. Usually called messaging connections.
  • Implicit messaging connections provide dedicated, special-purpose communication paths (ports) between a producing application object and one or more consuming application objects. Usually called I/O connections.

Both types of connections can be linked between networks.

Electronic Data Sheet (EDS) File

Every Ethernet/IP device has an EDS file to configure the device. Different control software tools use the text EDS files to identify and understand the properties of an EtherNet/IP device (device type, product revision, etc).

Often vendors will store the EDS file into the device memory, this allowing users or tools to upload it directly.

User Difficulties with EtherNet/IP

  1. Require understanding of both the IT fundamentals and control network (OT).
  2. Complex big networks – The EtherNet/IP network are expanding in every network, new devices are added every day and so the planning of the Ethernet infrastructure is essential for better performance and maintenance. Picking the correct routers, switches and documenting the network perfectly.

Conclusions

The EtherNet/IP has few competitors including Modbus/TCP, Profinet, and EtherCAT. These competitors can’t provide the vendor support, flexibility and architecture support proposed by CIP over Ethernet.

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