Update from the Time Sensitive Network (TSN) Testbed
by Florian Frick (ISW – Stuttgart), chair of the IIC TSN Testbed
IIC Blog Post
Connectivity is a key requirement for digitalization and the most important driver for innovation across many industries. While open standards are typically used in the IT world, industries with deterministic requirements such as production, automotive and professional audio/video tend to use proprietary, specialized systems with limited interoperability. Time-Sensitive Networking (TSN), the next evolutionary step of IEEE Ethernet, combines the benefits of a flexible IT network with deterministic guarantees and is, therefore, a critical enabler of digitalization.
The Industry IoT Consortium’s TSN Testbed has been actively contributing to establishing a TSN-based ecosystem since 2015. It provides a platform for collaboration, discussion, prototyping, and testing, with a particular focus on cross-vendor interoperability. Pre-pandemic, over 30 members met multiple times a year for Plugfests at the European (Institute for Control Engineering (ISW) – University of Stuttgart, Germany) and North American (Vanderbilt University, Nashville) testbed host locations.
Recently, after an enforced break of two years, some group members (Calnex, Belden/Hirschmann, Intel, Keysight, Kontron, Mitsubishi Electric, Mobatime, NetTimeLogic, SoC-e) were able to meet again for a Plugfest. While the main focus was on implementing the plans and ideas discussed through the “virtual years,” interop testing and device and network performance evaluation were also key objectives.
Testbed activity is based primarily around the Interop Rack. This remotely-accessible, permanent setup integrates a core network infrastructure, devices under test (DUTs), test tools, and various other capabilities. By simply modifying the physical connections between the DUTs and the core network, various interoperability scenarios can be set up quickly and reproducibly. The Testbed team has defined test plans that can be applied to a scenario to analyze aspects like time synchronization, network configuration, and schedules. The TSN Testbed is agnostic of higher-layer network protocols. However, since the layers affect each other, various combinations and configurations are tested either in isolated setups consisting of similar stack-ups or in interoperability scenarios, combining different devices and higher-layer protocols. The protocols and ecosystems of interest include OPC UA and CC-Link.
A testbed scenario at the recent European Plugfest analyzed the performance of a network incorporating the maximum available number of devices from the attending companies. A topology was set up as depicted in Figure 1, integrating seven devices from five vendors in a chain, plus additional end station devices on the side of the main path. A Pulse-Per-Second (PPS) and a protocol-based-measurement were taken using a high precision measurement tool, Calnex Paragon-X, to observe the synchronization performance of the PTP (Precision Time Protocol). Additional PPS signals along the chain were monitored using a PPS analyzer from NetTimeLogic. To load the network, traffic was injected across the topology using a Keysight/Ixia Novus One, reaching a bandwidth up to 90% of the available capacity.
Figure 1: Topology of the test scenario. All switches different products from five vendors.
Happily, interop and synchronization performance exceeded requirements and expectations. Not only was the 802.1AS end-to-end time synchronization performance limit of 1 µs achieved, but synchronization within around ±100 ns was observed in a stable state network. Figure 2 shows 1PPS measurements from various time-aware end station devices attached to the core network topology.
Figure 2: PPS accuracy measurement with NetTimeLogic’s Universal PPS Analyzer (Grey: Reference PPS, Colored: PPS from the devices under test).
While TSN has already made it to the core of the digitalization strategy of many companies, the technology now available is proof that TSN is not just a future vision but is, in fact, a current reality. Most device vendors will bring devices to the market throughout 2022 to provide the building blocks for real-world setups.
For those who want to enhance their own developments, the Industry IoT Consortium (IIC) TSN Testbed is the right place to be and is always open to new participants: whether chip vendors, system integrators, software developers, or test equipment companies, everyone can benefit from early interoperability testing and the opportunity to interact with others in the same field.
For more information or to understand how you can become part of the IIC TSN environment, please contact the testbed chair Florian Frick or the IIC staff.