Industrial Ethernet: Moving toward a Single Network Vision

Single-pair Ethernet and IETF/IEEE standards are spurring work on a harmonized network based on Ethernet, Internet Protocol, and the related open ecosystem.

At the recent ODVA technical conference, the key takeaway was that standards are emerging that will leverage Industrial Ethernet network convergence and edge devices to accelerate the migration from traditional field buses to Industrial Ethernet. New technologies including Single Pair Ethernet, Time Sensitive Networking, and constrained node devices/networks are seen as potentially impacting the use of Industrial Ethernet—in conjunction with EtherNet/IP—as we move into the future.

IETF and IEEE Standards, Ethernet, IP and Open Ecosystem, networks

Manufacturing applications could benefit from constrained EtherNet/IP in four key areas: in-cabinet components, on-machine components, process automation, and low-power wireless solutions. (Image source: ODVA)

Ethernet, IP, and Open Ecosystem

The argument is that, while Industrial Ethernet has exhibited rapid growth in recent years, field buses and sensor networks are still widely used. In addition, many potential network nodes remain hardwired. However, end users understand and will seek the advantages of a harmonized network based on Ethernet, Internet Protocol (IP), and the related open ecosystem. Potential benefits include reduced complexity and cost by minimizing the use of gateways and eliminating hardwiring, along with improved optimization and maintenance using cloud connectivity and analytics.

But unfortunately, there are also barriers to the single network vision. So while usage of a mix of EtherNet/IP, field buses, and hardwired nodes continues, open standards backed by IETF and IEEE are offering new alternatives. According to the technical paper, “Enhancements to EtherNet/IP for Constrained Devices and Networks,” which was presented at the ODVA conference: “IoT opportunities led IETF to create IP-stack optimizations for constrained devices and networks (RFC 7228). Enhancements are applicable to both low power wireless (6TiSCH) and wired networks, eliminating TCP overhead (UDP-only), compressing messages (6LoWPAN), expanding the address space (IPv6), optimizing security (OSCORE), and shrinking the Web server (CoAP).”

The idea is that “the resulting Single Pair Ethernet suite offers reduction in wiring, node cost, size, and power consumption, delivering communication and power over a single pair.”

Three key markets are driving volume, providing the opportunity for industrial users to leverage these technologies. This includes use of single pair Ethernet in automotive industry applications, building automation like smart LED lighting, and process automation.

Barriers to the Single Network Vision

Key barriers to this vision are that many edge devices are constrained by low cost, size (small photo-sensors, for example), or power (densely packed or battery powered). Additional concerns include wiring costs and a requirement for long cable distances.

IETF and IEEE Standards

IETF has introduced related standards and drafts for constrained nodes and networks that are seen as potential building blocks for creating more effective solutions. Key technical points include: elimination of TCP overhead (UDP-only); compression of message headers; expansion of the address space (IPv6); optimization of security (OSCORE); and shrinking the web server (CoAP).

The IEEE has also been working to develop a family of Single Pair Ethernet (SPE) standards, enabling communication and optional power over a single pair to help address issues with wiring, node cost, size, and power consumption challenges.

A new standard (IEEE P802.3cg) with an estimated completion date late in 2019 aims to introduce a pair of 10 Mbit/s SPE PHYs targeting constrained applications. 10BASE-T1L focuses on process automation instruments by offering distances to 1000 meters, intrinsic safety compatibility, and support for legacy wiring. In contrast, 10BASE-T1S is focused on replacing the CAN, CAN FD, MOST, and FlexRay protocols in automotive applications, along with hardwired components in industrial automation control cabinets. 

Constrained EtherNet/IP Explorations

New potential application areas for EtherNet/IP at the network edge are constrained applications for field devices with a focus on process automation, low power wireless, in-cabinet components, and on-machine components.

A number of options to reduce cost, size, and complexity are being explored. EtherNet/IP currently requires the use of both TCP and UDP in the network stack of a device. Using UDP only, for example, could result in a substantial reduction in stack complexity and messages. In typical CIP applications, encapsulation and CPF headers create significant overhead in EtherNet/IP messages. Low power wireless networks, such as IETF 6TiSCH, have constrained packet size, which is not able to carry the existing encapsulation header in a single wireless packet.

Current EtherNet/IP communication does not support constrained device and network requirements. But there is a proposal to develop a constrained EtherNet/IP communication profile.

For more information on this topic, read the complete technical paper on the ODVA website.

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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