EtherNet/IP versus PROFINET
Contributed By Digi-Key's North American Editors
Adoption of industrial Ethernet continues to outpace other options as companies become digitally connected. That’s especially true where Internet of Things (IoT) functionality is employed in automation and industrial control systems to boost data accessibility and usability. EtherNet/IP and PROFINET are the top options here.
Structure of EtherNet/IP and expanding EtherNet/IP applicability
EtherNet/IP is an industrial network protocol that employs the Common Industrial Protocol (CIP) to standard Ethernet. It works on a network application layer — which (in the two conceptual models of networks) is at the “topmost” device and user-facing layer to allow communication between controls and input-output (I/O) devices. More specifically, EtherNet/IP is the top layer of the Open Systems Interconnection (OSI) and transmission control protocol/internet protocol (TCP/IP) models.
Figure 1: The two most common models used to describe networks are the OSI model and the TCP/IP model. (Image source: Design World)
- The application layer just mentioned
- An Internet Protocol networking layer
- The standard Ethernet link layer
Note that the IP in EtherNet/IP is short for industrial protocol and refers to network protocols originally developed to allow communication over serial connections such as RS-232 and RS-485 — both standards for industrial data transmission. Many such connections now operate over Ethernet using protocols such as TCP/IP, so common for Internet communications. EtherNet/IP communications and its very standardized hardware (including hubs, switches, routers, Ethernet cables, and Ethernet network cards) is defined by the IEEE 802.3 Transmission Control Protocol and the Internet Protocol.
Developed in 2009, EtherNet/IP arose from collaboration between the Open DeviceNet Vendors Association (ODVA) and ControlNet International (CI) under the auspices of ODVA and its members. ODVA itself was founded in 1995 as a consortium of automation companies (including Rockwell Automation, Cisco, Schneider Electric, Omron, and Bosch Rexroth) to advance open and interoperable communications for industrial automation. According to ODVA, EtherNet/IP leads industrial-Ethernet adoption — representing 25% share of market in 2017 and 28% in 2018 with the most nodes of industrial Ethernet networks shipped.
At present, EtherNet/IP is one of four ODVA networks that have adopted CIP for industrial networks. The others are DeviceNet, ControlNet, and CompoNet.
CIP is a conduit of organizing and sharing data in industrial devices. More specifically, it uses different types of messages and services to exchange data in industrial automation applications that include process and system control, safety, synchronization, motion, configuration, and information. CIP lets these applications integrate with enterprise-level Ethernet networks and the Internet. It is a unified communication network used for manufacturing and industrial applications and widely adopted by vendors around the world.
For industrial protocols, data is ordered as objects with data elements or attributes. These data objects typically sort into required objects and application objects. The former are found in every CIP.
Figure 3: EtherNet/IP and PROFINET are leading industrial Ethernet protocols. Both are supported by the ODVA. (Image source: ODVA Inc.)
EtherNet/IP is rather easy to implement, and it’s compatible with standard Ethernet switches for industrial automation. However, the basic form of EtherNet/IP is non-deterministic and therefore unsuitable for strict real-time industrial applications. CIP Motion can complement EtherNet/IP to help the latter satisfy demanding requirements for deterministic real-time control (including closed-loop motion control) with unmodified Ethernet in full compliance with IEEE 802.3 and TCP/IP Ethernet standards.
EtherNet/IP complemented with CIP Motion technology delivers multi-axis distributed motion control. It is scalable and offers a common application interface for motion designs.
Data transmission via EtherNet/IP
TCP and the user datagram protocol (UDP) are the underlying communication protocols of the Internet and many private networks as well. EtherNet/IP employs a TCP port for what is called explicit messaging. Such messaging is when the system sends data to a client in response to a specific request for that data. It uses TCP/IP — a connection-oriented protocol that explicitly manages links between clients and servers. Core to TCP/IP networking, TCP helps fragment data packets so that data messages reach their destination. Note that IP deals only with packets; TCP lets two hosts establish connection and exchange data streams. TCP guarantees delivery of data as well as that packets will be delivered in the order in which they were sent.
EtherNet/IP employs a UDP port for implicit messaging — system communications sent from preset memory locations to a controller or other client at some prescheduled interval. Such communications are far faster than explicit messaging, and the one-way data transmission of UDP connections (sans validating receipts) simplifies cyclical system updates.
PROFINET for deterministic communications
PROFINET is another technical standard that defines a mode of data communication via industrial Ethernet. PROFINET modifications to standard Ethernet ensure proper and prompt data transmission even in challenging applications. Its definitions dictate a means of data collection from industrial equipment and systems to satisfy specific and often tight time constraints. PROFINET arose from PROFIBUS — a standard for fieldbus communication to support automation. While PROFIBUS is a classical serial fieldbus based on industrial Ethernet, PROFINET goes further with additional capabilities to allow faster and flexible communications to control automation components.
Figure 4: EtherNet/IP is most common in the United States. PROFINET is widely used in Europe. (Image source: PI North America)
In fact, PROFINET had 30% of the industrial-network market share as of 2018, making it the world’s leading Ethernet-based communication solution for industrial automation. More than five million PROFINET-ready devices come to market every year.
PROFINET and PROFIBUS communications are deterministic, which allows support of automation systems with precise I/O structure limits … and their defined I/O structures allow precise calculation of maximum update times. PROFINET can also provide isochronous real-time (IRT) data exchange. IRT essentially leverages the ultra-precise time clock of PROFINET to prioritize the passage of some types of data traffic and buffer the rest. IRT excels in demanding applications such as motion control and other applications that need more deterministic operation than real-time operation. In a real-time data exchange, bus cycle times are less than 10 msec. In contrast, IRT data exchanges occur within a few dozen μsec to a few msec.
For example, PROFINET in a packaging and labeling operation can support data transmission to ensure bottles are filled to a precise level in less than a second — to within just an msec or so. PROFINET can also detect, quantify, and alert operators of any anomalies in the bottling process and immediately shutdown processes as well.
Side note on PROFINET hardware
Standard Ethernet is only suitable for data transmission in home, office, and select industrial-monitoring settings. In contrast, the industrial Ethernet of PROFINET is suitable for installation in harsh industrial facilities requiring deterministic data communications. PROFINET cables and connectors differ from those employed in standard Ethernet — and includes connectors with heavier lock mechanisms and ruggedized industry cables. PROFINET routers (whether integrated into other hardware or built as standalone elements) function on network layer three (from the network models mentioned earlier) and communicate using IP addresses. These routers connect local area networks (LANs) and form wide area networks (WANs) while employing algorithms to determine the best data-transmission routes between networks. Some PROFINET switches also employ fiber-optic connections. These ultra-fast components integrate PROFINET-capable devices into Ethernet networks (or PROFIBUS) via gateway elements for copper-to-fiber-optic conversions.
Figure 5: PROFINET hardware excels in harsh and severe conditions subject to vibration, heat, dust, oil and other challenging conditions. This Brad PROFINET IO-Link HarshIO module is one example of a ruggedized component for PROFINET-connected factory automation. (Image source: Molex)
PROFINET managed and unmanaged switches
PROFINET switches work on the second data layer of the conceptual network model covered earlier. They function to control the receipt and transmission of data signals through the network.
Unmanaged PROFINET switches send incoming Ethernet data through the proper ports connected to intended device endpoints. Ports may have an LED indicator to show the presence of data flow, but these unmanaged switches usually don’t provide much more information about or management of that data flow.
In contrast, managed PROFINET switches are more intelligent and work with different IT protocols — including the simple network management protocol (SNMP) and link layer discovery protocol (LLDP) for PROFINET. Because of their intelligence, managed switches are often used where preventing downtime is a top objective — and where troubleshooting failures is useful. Of course, they're usually costlier than unmanaged switches.
Direct comparison of EtherNet/IP and PROFINET characteristics
Industry-specific adaptations of EtherNet/IP are transforming many industries. For example, the packaging industry employs EtherNet/IP for high-speed communications, determinism, and real-time performance. Industries such as chemical processing, traditional automation, and power generation use EtherNet/IP to continually quantify output. Still other industrial applications involve fully automated processes that necessitate counting and real-time data acquisition for control. Here both EtherNet/IP and PROFINET excel in creating the deterministic networks such applications require.
Consider EtherNet/IP and PROFINET signal qualities, message sizes, and update rates for details on how the two differ. PROFINET is generally faster than EtherNet/IP and most often deployed with standard hardware … though PROFINET IRT requires specific hardware. EtherNet/IP is more interoperable, as it’s based on object-oriented programming and relies on commercial off-the-shelf (CotS) components. In fact, that use of CotS components and hardware not unlike the ubiquitous variations employed in office settings means EtherNet/IP is very cost effective for high-speed industrial connectivity. Economies of scale and the interchangeable nature of much of this hardware help minimize upfront costs the most.
In contrast, PROFINET-ready components can integrate into PROFIBUS-based fieldbuses, effectively capable of supplementing existing systems without necessitating complete replacement. There are cost benefits to the way existing devices can be shared and existing networks accept the addition of supplemental hardware. Even so, upfront costs for PROFINET technologies may be up to 15% more than those based on EtherNet/IP. That cost is partially offset by easier installation, estimated to be about half as complicated (read: expensive) as installation of Ethernet/IP.
Topologies and components supported by EtherNet/IP and PROFINET also differ somewhat. Network topology is the arrangement of the links and nodes of a network. Links are wireless and wired technologies such as coaxial, ribbon, and twist-pair cable as well as fiber-optic cable. In contrast, network nodes are hubs, bridges, switches, routers, modems and firewall interfaces. Topologies include star, line, ring, daisy chain, and mesh.
EtherNet/IP networks primarily use a star topology complemented by others: Ring topology connects multiple devices sequentially — though if a cable is cut within the ring, each device maintains its path to control. Tree topology uses devices or switches wired with connections between device groupings; any break prompts an algorithm to determine the next best workable path to solution.
PROFINET’s line topology uses minimal cabling and no external switches; connections to any star and tree topologies are via standalone switches. Here if a star or tree switch fails, communications to all nodes are affected — which can be problematic. So to ensure communications continuity, PROFINET supports topologies with added devices to provide media backup and other elements should a cable or node fail.
Note that EtherNet/IP and PROFINET networks deploy in systems under centralized and decentralized control — and sometimes work in systems that combine both control arrangements. With EtherNet/IP and PROFINET, centralized systems use a client-server setting having a center server connecting one or more client nodes. Client nodes submit requests to the central server rather than process on their own while the server handles all the major processing. In decentralized systems, every node autonomously executes its own logic. The final actions of the system are the sum of all nodes’ logic.
EtherNet/IP and PROFINET gateways
Gateways (whether standalone pieces of hardware or integrated with router, firewall, or server functions) control the flow of data in and out of a given network and sometimes between disparate systems. That includes some gateways that are specifically designed to communicate I/O between EtherNet/IP and PROFINET networks. For the latter, most gateways function as a PROFINET device and EtherNet/IP adapter for automatic compatibility.
Besides their primary role, gateways can also unburden a system’s PLC of signal timing, counting, calculating, comparing, and processing tasks. EtherNet/IP and PROFINET gateways with router functionality let computers send and receive data over the Internet. Today, smart human-machine interfaces (HMIs) connected to networks sometimes do double-duty as gateways between automation systems and controllers as well — for simplified system commissioning and maintenance.
Connecting future industrial automation installations
EtherNet/IP and PROFINET connectivity are enabling innovative new permutations of automation and industrial controls with unprecedented agility and IIoT functionality. As hardware, software, and connectivity technologies leverage EtherNet/IP and PROFINET in new ways, they’ll help systems meet evermore-demanding industrial production requirements.
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