Given the overwhelming success of DeviceNet, it's not surprising that ODVA and Rockwell Automation would be interested in pursuing technology solutions for implementing Industrial Ethernet at the device level. The result is a push to explore enhancements to EtherNet/IP for constrained networks and devices, and ultimately pursue the possibilities and advantages of a harmonized network based on Ethernet, IP, and the related open ecosystem.
A constrained EtherNet/IP stack could reduce device network node costs by eliminating complexity and leveraging open standards to implement both wired and wireless systems. (Source: ODVA)
The potential benefits of this technology could be immense, including reduced complexity and lower costs for devices by minimizing use of gateways, elimination of hard wiring, and improved system optimization and maintenance using cloud connectivity and analytics.
ODVA Technical Conference
At the most recent ODVA technical conference, one of the presentations discussed the barriers to this single network vision along with a series of exploration areas that could help make this a reality. The authors of the paper include David D. Brandt, senior principal engineer and Dayin Xu, senior research engineer at Rockwell Automation along with Dr. Jörg Hähniche, head of Development & Integration Services, and Matthias Dietrich, software engineer at Endress+Hauser Process Solutions AG.
The conclusion of the paper is that the open standards are offering new techniques that can be brought to bear in this area to overcome barriers primarily related to cost and complexity. A number of factors are potentially coming together to advance the prospects of EtherNet/IP specifically for use with “constrained” networks and devices. These include:
- Unprecedented IoT opportunities have led the IETF standards organization (www.ietf.org) to create IP-stack optimizations for constrained devices and networks (RFC 7228).
- Enhancements are applicable to both low power wireless (6TiSCH) and wired networks, and offer open standard solutions.
- Possibilities include elimination of TCP overhead (UDP-only), new abilities to compress messages (6LoWPAN), expansion of the address space (IPv6), security optimization (OSCORE), and an ability to shrink the web server used on devices (CoAP).
The paper states that: “numerous industries flooded into IEEE to develop enhancements for enabling Ethernet to displace other networks at the edge. The resulting Single Pair Ethernet suite offers reduction in wiring, node cost, size, and power consumption, delivering communication and power over a single pair. A 1000 meter variant targets process plants and other large sites. A deterministic Ethernet bus variant targets very constrained devices, such as in-cabinet components.”
With the Internet of Things creating opportunities and major markets such as automotive, for example, moving towards an all-Ethernet vehicle, major organizations are promoting expansion of Ethernet and/or IP at the edge. Key industry participants have formed the OPEN (One Pair EtherNet) Alliance to promote a variety of Single Pair Ethernet (SPE) solutions, and are working toward open standards solutions within the IEEE.
Other market application areas including smart LED lighting and process automation have also been working on industry-specific solutions. Work within IEEE on Single Pair Ethernet (SPE) is anticipated to deliver Ethernet communication and power over cables as long as 1000 meters (including many installed cables) into intrinsically safe environments.
Key Technical Takeaways
A number of constrained EtherNet IP application areas addressed in the paper that have applicability to smart manufacturing include in-cabinet and on-machine implementations, process automation and low power wireless systems.
An interesting technology possibility is use of UDP only in these systems as a way to reduce cost and complexity. EtherNet/IP currently requires the use of both TCP and UDP in the network stack of a device. While TCP does have advantages, it also adds additional resource requirements. TCP is connection-oriented; the stack needs to keep track of each single client connected to the device and buffer messages in case packets are lost on the network and need to be retransmitted.
According to the paper, “Using UDP-only can result in a substantial reduction in stack complexity and messages. A UDP-only prototype demonstrated about 30% savings in Flash and RAM in a constrained device. Such a reduction can mean a device uses one size smaller MCU, reducing cost, size, and power.”
While work on these solutions is ongoing and the presenters at the ODVA conference emphasized that we are in the early stages of development, this is a technology area to keep an eye on because of its potential to create enormous, long-term benefits.
Here’s a link to the complete technical paper presented at the ODVA conference: Enhancements to EtherNet/IP for Constrained Devices and Networks.
Al Presher is a veteran contributing writer for Design News, covering automation and control, motion control, power transmission, robotics, and fluid power.
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