Time Sensitive Networking: A Silver Bullet for the Industrial Internet of Things?

The Industrial Internet of Things and the Role of Ethernet

The IoT is not strictly a consumer-facing phenomenon. For the automation industry, the building blocks of something akin to the IoT—an Industrial Internet of Things, as it has been labeled in some circles to differentiate it from its more general counterpart—have been in place for a while, even if there isn’t overarching standardization like there is with something like the internet. Embedded sensors, machine-to-machine communications, and industrial Ethernet protocols like EtherCAT®, PROFINET®, and many others have enabled sophisticated applications such as high speed manufacturing, multiaxis motion control, and other robotics. So, what’s next as automation and the IoT intersect?

Accenture has estimated that the Industrial Internet of Things could add more than $14 trillion to 20 major world economies over the next 15 years (for example, it could boost U.S. GDP by 2% by 2030).1 With that said, there are significant challenges to realizing this potential in the IIoT. In addition to the slow progress on the IIoT reported by 71% of the respondents to Accenture’s study, there’s also the issue of reconciling different networks and ensuring determinism; enter initiatives such as the time sensitive networking extension to Ethernet from a dedicated IEEE 802.1 working group.

“For the Industrial IoT to work, we need a set of standards everyone can conform to and get the data flowing,”2 observed Dan Sexton, project leader at GE Global Research, according to EE Times. “Ethernet has tended to be a rallying point for industrial systems, but there have been concerns over a lack of determinism. The goal of TSN is to resolve the problems and create an even stronger rallying point.”

TSN, Audio Video Bridging, and Determinism

TSN is designed to operate at the physical layer and it is an evolution of audio video bridging, the set of technical standards for low latency, high bandwidth distribution of audio, and video data over an Ethernet backbone. AVB has also been touted for its potential in automotive applications like on-board infotainment systems. The Avnu Alliance has widely promoted product certification and conformance testing for AVB in order to standardize its implementations.

On a more technical level, AVB allows for precise time synchronization using the IEEE 1588 precision time protocol. It can also reserve bandwidth for individual applications in order to set up a guaranteed level of latency and zero congestion loss for audio and video streams. In this way, AVB addresses the nondeterministic character of standard Ethernet and instead facilitates the determinism needed for real-time data distribution.

How does TSN fit into this picture? In the most basic terms, its IEEE task group is now looking to bring AVB’s essential characteristics to industrial automation and control via TSN. With TSN in place, both standard and low latency control Ethernet traffic can run on the same network, with the technologies for Ethernet communications, synchronization, and deterministic data transfer converged into a single new protocol.

For the IIoT, the ultimate transition to TSN could enable in-plant benefits such as:

  • Seven-nines (99.99999 percent) reliability
  • Plug and play time synchronization with less than 1 microsecond of jitter in normal conditions and worst-case delays of under 4 microseconds
  • General simplification and strengthening of IEEE 1588 implementation
  • Reservation of quality of service for data streams, regardless of their higher layer protocol or status as unicast or multicast
  • Alternative paths and instantaneous switchover so that data streams avoid packet loss in the event of equipment failure
  • Scalability for large systems due to reduction of management traffic for bandwidth/configuration reservations

The last point is important, considering the expected scope of the IoT in both consumer-facing and automation industry capacities. Tens of billions of new devices are expected to connect to IT and industrial networks in the next decade plus.

Mark Hoske noted as much for Control Engineering last year, when he asked what the world would be like if “every rail line were a different gauge, or every outlet carried a different voltage, or every smartphone brand used a different wireless protocol.”3 For industrial automation and control, TSN ideally provides a route past such fragmentation and toward deterministic, scalable, and standard network performance. 

Ссылки

1 Valley Voices. “Transforming Economic Growth with the Industrial Internet of Things.” Forbes, 2015.

2 Rick Quinnell. “Alliance Prepping for Ethernet in the Industrial IoT.” EE Times, 2014.

3 Mark T. Hoske. “Developments to Watch: Will One Super Network End Ethernet Wars?Consulting-Specifying Engineer, 2014.