Industry groups prepare Ethernet for operational wireless networks


As Ethernet networks continue to evolve, two industry groups recently announced plans to take them to the next level – this time by expanding the technology to urgent operational and wireless communications applications.

This week, the Ethernet Alliance said it was pushing an effort to bring faster, simpler communications to operational technology (OT) networks typically found in building and automation environments. industry. The Ethernet Alliance includes a variety of communications players including Broadcom, Cisco, Dell, Juniper, Intel as well as academic and industry members.

A recently standardized IEEE specification, 802.3cg, which defines the use of Single Pair Ethernet (SPE) in many circumstances rather than a wide range of fieldbus cables, including RS ‑ 485 twisted pair cables, RG ‑ 6 coaxial and instrumentation, is at the origin of the group’s strategy.

Ethernet over twisted pair

OT networks have historically been isolated from Ethernet-based computer networks, and “these networks, while functioning efficiently today, use outdated and disparate network protocols. They are slow, typically 31.2 KB / s, and require translation gateways to convert the necessary data to Ethernet. SPE is uniquely designed to meet the challenges and topologies of OT networks, ”said Peter Jones, president of the Ethernet Alliance and senior engineer at Cisco.

“The IEEE 802.3cg specification, released in February 2020, is the standard we’ve always needed for OT networks,” he said. The alliance wants to help apply the standard to increase the value of OT networks and improve business outcomes. The ultimate goal is an enterprise-wide single protocol network that meets the needs of IT and OT. “The convergence of these two networks is essential to achieve the goals of Industry 4.0.”

The IEEE 802.3cg working group paid special attention to the needs of OT networks when creating the “cg” standard. Many proprietary implementations have some common elements. Most are electrically RS-485 compliant, have two main topologies, and share a common physical layer, a twisted pair cable. SPE leverages these common elements to create a way to embrace Ethernet and all of its benefits without “reinventing the wheel” so to speak, said Bob Voss, SPE Subcommittee chair and senior senior engineer at SPE. Panduit.

“SPE allows users to build the facilities served by OT networks the way they know they work best; SPE is designed to support proven topologies and even uses a similar physical layer. Many SPE experts believe, given the health of the cables, that it might be possible to reuse physical layer elements from current OT networks, ”said Voss.

In the past, the application of Ethernet in OT networks required adapting the network to work with normal BASE-T Ethernet. It was effective but created barriers, which limited adoption. SPE is breaking down those barriers, Voss said.

“Additionally, one of the problems with current proprietary occupational therapy protocols is an impending skill shortage. The tribal knowledge that sustains these important networks is ingrained in the minds of people who have reached retirement age. This creates a huge risk of business continuity. And, as businesses want smarter buildings to create more enjoyable and productive workspaces, higher functionality is needed in OT and Ethernet networks is a key enabler, ”said Voss.

Time-sensitive wireless networking

In the offline world, the rise of 5G and 802.11 development has sparked interest in extending time-sensitive networking (TSN) technology from Ethernet to wireless.

The push to merge wireless and TSN Ethernet comes from the Avnu Alliance which says its members include over 95% of silicon Ethernet vendors as well as the automotive industry and AV vendors. Its subsidiaries include Cisco, Intel, Bose, Bosch and Extreme. The Avnu Alliance defines interoperability requirements and is the certification authority – grants certification for interoperable products – for TSN. The Alliance does not do the actual physical testing of the products; this is managed by a network of registered test facilities. For example, the University of New Hampshire Interoperability Laboratory is a registered test facility.

TSN is a collection of standards developed by the IEEE 802.1 TSN Working Group, which defines a new set of mechanisms to provide time synchronization and opportunity (deterministic data delivery) for time sensitive data in a local area network shared with d ‘other types of applications at best. said Dave Cavalcanti, chair of the Avnu Alliance Wireless TSN working group and senior engineer at Intel.

TSN standards define new features for 802-based LANs, such as traffic shaping, frame preemption, traffic planning, ingress policing, and transparent redundancy. When all parts of a network are operating with the same sense of the reference time, traffic can be coordinated according to a time-sensitive schedule, a method that allows better control of latency for traffic at critical time. These new features provide a whole new layer of control for managing traffic over Ethernet, Cavalcanti said.

According to Cavalcanti, IEEE 802.1 TSN standards have experienced strong growth over the past three to five years, especially in the industrial market.

Wireless communications using TSN not only allow mobility, they are flexible and reduce cabling costs. “TSN’s wireless capabilities, for example, can allow manufacturers to easily reconfigure industrial automation and control systems, as well as optimized routing and use of mobile robots and automated guided vehicles,” Cavalcanti said. Industrial automation system and mobile robots are important use cases because wireless is fundamental for mobility, flexibility and reconfiguration of tasks and routes.

“Power grid systems are another interesting use case for wireless TSN, as these systems have varied coverage areas that can vary from local areas (e.g. substation) to large areas (distribution and transmission). Industrial control systems could also benefit from wireless connectivity, but they will require the highest level of determinism and reliability and will rely exclusively on timing planning (IEEE 802.1Qbv) over wireless links, ”Cavalcanti said.

There are some challenges in implementing TSN wireless extensions.

Interference is usually the number one concern when it comes to TSN wireless extensions. Susceptibility to malicious jamming is also often raised as a concern, Cavalcanti said. “While the magnitude of the threat must be considered in each specific wireless deployment and application, it is important to enable the tools to mitigate the potential impact of interference (malicious or otherwise) in a TSN wireless domain. . Because TSN is based on Ethernet and wireless standards (IEEE 802.11 / Wi-Fi and 5G), networks can take advantage of the best practices and security standards that have been developed for Ethernet, 802.11 and 3GPP systems.

An additional layer of security for TSN can also be added with precise timing mechanisms that facilitate early detection of a network violation as defined in the IEEE 802.1Qci specification. 802.1Qci capability identifies time-sensitive flows and uses timing and scheduling information to accept or reject packets. The correct package must arrive in the correct time window at the correct port to be accepted. This capability must also be extended to wireless networks, Cavalcanti said.

“Finally, not all wireless technologies currently can (or should) support TSN functionality. Given the current and future wireless capabilities of Wi-Fi and 5G, for example, use cases that require high-speed mobility over large areas are not yet considered practical for wireless performance. TSN level, ”Cavalcanti said.

TSN is a network layer that leverages the underlying data communication technologies (such as Ethernet, 802.11 / Wi-Fi, and possibly 5G). As such, TSN can be viewed as a unifying layer operating across and potentially integrating heterogeneous connectivity technologies. TSN’s role is to ensure end-to-end data delivery with determinism, Cavalcanti said. “Each of the individual connectivity technologies may implement its own functionality to help achieve TSN’s goals, but TSN has a broader reach than any particular connectivity technology. “

Despite the momentum and progress of other industry players, more effort is needed to commercialize TSN wireless capabilities. For example, wireless-specific TSN configuration interfaces, parameters and test procedures still need to be developed, Cavalcanti said. “This is why we have formed the Wireless TSN working group within the Avnu Alliance. The work of the WTSN working group highlighted the importance of starting early discussion and alignment on topics such as consistent TSN interfaces for wired and wireless technologies, interoperability testing and certification efforts. .

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