Questions About Time Sensitive Networking

Time-Sensitive Networking's star has been on the rise with its promise to bring determinism via standard Ethernet to the plant floor. In contrast to the positive news surrounding the technology, some are questioning the extensibility of its benefits and its cost.

In the space of a decade, industry moved from a widely held view that Ethernet is not suitable as a plant floor network to broad acceptance that, not only is it appropriate for the plant floor, it is well on its way to becoming the de facto plant floor networking technology. Though much of this change has been driven by the ongoing integration of plant floor and enterprise system data, the rise of Time-Sensitive Networking (TSN) has also played a key role in solidifying Ethernet’s future use in the plant.

With its ability to ensure determinism over standard Ethernet, and with support from major technology suppliers, TSN appears to more than adequately address plant floor concerns about Ethernet’s determinism and reliability. But a recent report from Global Market Insights, a market research and management consulting company, calls into question some of the benefits of TSN.

According to a press release issued by Global Market Insights, its report notes that the high degree of standardization inherent in TSN “limits the ability to provide customized solutions” and that the technology requires “additional dedicated circuitry, which increases the overall cost.”

This is not meant to imply that the report is entirely negative with regards to TSN. In fact, it reinforces some of TSN's positive aspects noting, “The use of this technology enhances latency-sensitive applications [such as motion control], making it an apt choice for industrial automation.”

However, considering this is the first report I’ve encountered that questioned TSN in terms of how it could limit customizability and increase cost, I reached out to some of my contacts who have been most vocal in support of TSN to gauge their reaction to Global Market Insights’ assessment.

Addressing the standardization issue raised by Global Market Insights, Oliver Kleineberg, Belden’s global chief technology officer for core networking, was emphatic that the advisory group is incorrect in its assertion.“The exact opposite is the case,” he said. “It is true that the TSN technology is highly standardized, but this is true for Ethernet as a whole. It is a necessity to achieve the high level of interoperability we see in today’s automation networks.”

As for the impact of Ethernet’s standardization on customizability, Kleineberg said, “The differentiation for players on the TSN market comes from functions that are not associated with the basic protocol functions—for example, value-add functions like easy deployment and configuration, or functionality on top of TSN that cater to a specific target market. In addition, [with TSN] end device manufacturers can rely on a stable network where they can ensure their end devices have a large, available market and are not constrained by technology barriers while, at the same time, retaining their unique features like engineering, tooling and parameterization.”

The areas where customization is “really valued or needed is not on the network, but on the higher level applications," explained Todd Walter, chief marketing manager at National Instruments. "The protocol is viewed as the wrong place to customize [because] the value of getting converged networks allowing OT and IT to work better together is driving investment.”

“To say that standardization limits customization is a bit of a red herring,” said Michael Bowne, executive director of PI North America. “If a company chooses not to employ standardized TSN, that's certainly their prerogative—and this would not be surprising, since a preference for customized solutions has and always will exist. But it’s important to realize that standardization does not necessarily limit customization.”

Bowne also pointed out that users should realize that TSN is “not just one thing—it's a collection of six IEEE standards. This means that, if one company chooses to implement four out of the six while another company chooses to implement all six, yet both call it TSN, whose version would be considered standard?”

Walter added that industry’s convergence around OPC UA as a standard protocol for industrial communication supports his case that the protocol layer is not the area in which industry seeks customization. This makes sense, considering the years of fieldbus wars waged by technology suppliers that made integration projects more difficult—an unfavorable aspect of recent automation history that end users have been actively seeking to distance themselves from with the move toward Ethernet.

Despite their disagreement with Global Market Insights’ assertions about TSN’s standardization impacting customization factors, Kleineberg and Walter concur with the advisory group about TSN’s cost—to a point.

The advisory group’s assertion that TSN’s precise timing for the transmission of data frames requires the use of additional dedicated circuitry, which increases the overall cost, is “true to some degree,” said Kleineberg. He noted that the initial additional cost with TSN is typical with all new technology, “but the impact will very likely be negligible.”

Explaining the additional TSN cost factors, Kleineberg said, “Both the Precision Time Protocol function as well as the TSN Scheduling function require dedicated circuitry, which raises the complexity of silicon in Ethernet switching chips. However, due to the large market that is served with the TSN solution and the early buy-in from all major silicon manufacturers, the impact is expected to be very low. TSN-enabled silicon will carry a small premium for the early adopters. But since TSN is an Ethernet standard function, prices will quickly drop.”

Bowne concurred by saying, “most people believe TSN standardization will drive costs down because of the simple fact that the chips are no longer specialized for industrial networks—they’re all COTS [custom off the shelf]. Plus, the fact that other vertical markets are looking into the use of TSN, broader market use of the technology will mean increased competition and, therefore, lower prices.”

Kleineberg predicts the price drop process for TSN will be similar to the phasing in of other, now standard, technologies into switching chips, such as VLAN functionality.

Adding to Kleineberg’s comments about silicon costs impacting early pricing of TSN products, Walter said the process will be similar “to the transition from one Wi-Fi standard to the next as the latest work in IEEE is integrated. However, the hardware is not inherently more expensive.”

“Speaking for National Instruments, as we are about to announce our fifth product family supporting TSN, we found that our standard silicon suppliers were already providing TSN in the latest generation of their standard products,” said Walter.“For instance the Intel i210 NIC we use in our products was the next PCIe NIC on the Intel roadmap. It supports TSN features which we have integrated through our software to provide TSN capabilities to our customers. Neither we nor our customers saw an increase in cost over the previous generation due to the inclusion of TSN. Similarly, Cisco provides their customers the ability to update any standard IE4000 switch to support TSN by installing the latest firmware.”

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