Avik Bhattacharya
Ixia Product Development Manager
Blog

How to drag and drop industrial automation and control systems (IACS) traffic into your lab network

September 9, 2019 by Avik Bhattacharya

In my last 12 years’ experience of working in the networking industry, I’ve been lucky to work with many types of customers dealing with network design—network equipment manufacturers, Internet service providers, data center operators, in-vehicular network designers, industrial automation network managers. I have learned that every network transports a different type of traffic pattern. The traffic in the Google data center is very different from the traffic that a 5G fronthaul needs to carry. The traffic patterns are defined by:

  • The applications running on the network
  • The control protocols used in maintaining the network connections
  • The time-critical nature of the data being transported

Different types of critical control traffic and other traffic that is necessary for the manufacturing process are found in an industrial and process control systems network. Time synchronization and traffic engineering are two pillars of industrial network design to support the above traffic profile. The IEEE has defined a set of standards under the name of time-sensitive networking (TSN) that is like a toolbox for time-critical network design. On the other hand, the Industrial Internet Consortium (IIC) established the Time-Sensitive Networks for Flexible Manufacturing Testbed to display the value and readiness of time-sensitive networks to support real-time control and synchronization of high-performance machines. It has over 25 participants from a range of companies including chip vendors, IACS vendors, network infrastructure vendors, testing vendors, and certification organizations.

Challenges of manufacturing an Industrial Device

Industrial device manufacturers not only need to implement the right TSN standard, but also make sure those standards work under realistic conditions. I have always been very vocal about the need for system-level testing - in the whitepapers I wrote or in my presentations in technical events. But I often get questions about how to do realistic system-level testing. The challenge is to create a realistic traffic profile in the testing lab – in the development phase of an industrial device. The whitepaper from IIC titled Time Sensitive Networks for Flexible Manufacturing Testbed Characterization and Mapping of Converged Traffic Types provides an excellent definition of the types of traffic that can be present in an Industrial manufacturing network.

The IIC whitepaper focuses on the types of traffic flows that industrial automation and control systems (IACS) use and can affect the QoS of other traffic types. The traffic types discussed are network control, excellent effort, voice (audio), video, and best effort. Three sub-types of critical application traffic are defined - isochronous, cyclic, and events. 

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Image Reference: IIC Whitepaper - Time Sensitive Networks for Flexible Manufacturing Testbed Characterization and Mapping of Converged Traffic Types

The network engineer’s job is to ensure the industrial device under test (DUT) is able to handle all of the above types of traffic individually as well as all of them together.

So, the network engineer’s job is well defined and easy…but wait...

While the profile is well defined, how easy it is to emulate this in the lab? It requires sophisticated test tools to exactly recreate the interference of several time-critical flows running through a switch. The test tool not only needs to support underlying hardware capabilities but also provide ease of configuring the flows. 

Keysight’s Ixia TSN test solution, IxNetwork, takes it to the next level - allowing a user to drag and drop the IACS traffic profile into the test network. 

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IxNetwork 9.0 update 1 comes with a built-in resource for the IACS traffic profile. All the traffic types with possible frame sizes, periodicity, scheduling, and TSN mapping is automatically configured along with the control protocols like 802.1AS. Each traffic type can be individually enabled, suspended, or edited for designing a test.

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An Isochronous traffic example …

Let’s take an example of Isochronous traffic as defined in the whitepaper. This traffic should have a data delivery deadline within one data transmission period or cycle time. Typically, this type of traffic will be time scheduled in the network using the IEEE 802.1Qbv standard.

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Image Reference: IIC Whitepaper - Time Sensitive Networks for Flexible Manufacturing Testbed Characterization and Mapping of Converged Traffic Types

But the network will not have only this Isochronous traffic – it will also have other types of traffic that are unscheduled. The DUT or the system under test (SUT) should ensure the data delivery guarantee even in the presence of other traffic. IxNetwork provides a sophisticated way of measuring the traffic characteristics through the receive statistics at run time at line rate.

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In the above example, the Isochronous traffic is enabled in the presence of audio, video, and best effort traffic. The line rates are chosen in a manner so that it creates congestion in the DUT/SUT. From the statistics, we can see that the average latency of the Isochronous traffic is 339,012 ns, which is within the data delivery guarantee of 1ms cycle time or data transmission period. Also, the isochronous traffic is not incurring any loss due to the gate scheduling in the DUT/SUT whereas the best effort traffic is incurring 75% loss.

The above is just one example of traffic characteristics for data delivery guarantee. There are eight distinct characteristics defined in the IIC paper. IxNetwork has definitive methods for measuring each of those – which makes IxNetwork the most powerful and favored solution by the industrial device manufacturers all over the globe. 

Read more about the IxNetwork TSN test solution.