Time Sensitive Networking (TSN) Frequently Asked Questions

Publish Date: Nov 12, 2018 | 0 Ratings | 0.00 out of 5 | Print

Table of Contents

  1. What Is Time Sensitive Networking (TSN)?
  2. What Are Target Applications for TSN?
  3. Is TSN Ready for my Application?
  4. What Are the Benefits of TSN vs. Existing Methods? 
  5. How Is TSN Different from IEEE 1588?
  6. How Are Other Organizations Planning to Use TSN?
  7. How Is NI Working with Other Companies on TSN?
  8. Next Steps

1. What Is Time Sensitive Networking (TSN)?

Time Sensitive Networking (TSN) is an update to the IEEE Ethernet standard intended to address the needs of control systems with standard Ethernet technology. NI, Intel, Cisco, and others are collaborating in organizations such as IEEE, the Avnu Alliance, and the Industrial Internet Consortium (IIC) to define, standardize, and drive adoption of this new technology.

TSN will provide new features to standard Ethernet.  This includes standard time synchronization and deterministic network communication over standard Ethernet, allowing operations networks to leverage the advantages of traditional Ethernet while meeting the timing and control needs of control and measurement applications. By converging time-critical and best-effort data within standard Ethernet, TSN delivers cost savings and improved interoperability. As part of the Ethernet standard, TSN also benefits from continuing improvements in Ethernet security, bandwidth, and other capabilities and provides numerous advantages over today’s standard and specialty Ethernet protocols.

TSN is not a protocol; it is part of the Ethernet standard. Protocols such as OPC UA may be implemented on top of TSN.

Figure 1. Key Features of Time Sensitive Networking Technology.

 

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2. What Are Target Applications for TSN?

TSN provides distributed time synchronization and deterministic communication using standard Ethernet networks.  As such, any application requiring distributed measurements or control can benefit from TSN. Customers are using TSN for simple distributed synchronized measurements, embedded coordinated distributed data logging, advancements in next-generation computer numeric control machining, novel semiconductor processing machines, and future electrical grid research. A few more industries and applications include: 

Test Cells and Distributed Monitoring

Many measurement applications require sensor readings from multiple locations. To support analysis routines the data from each of the sensors needs to be correlated in time.  Applications such as structural test need to correlate the data from every strain gauge to get an accurate representation of the structure.  Similarly, in a distributed monitoring application such as monitoring flows or torsional vibration it may be necessary to have synchronization of the measurements, so machine health analytics can properly consume the data.  In these use cases the customers may only be using the time synchronization and not the deterministic communication capabilities.  This is fully supported in all NI TSN products (all TSN products from NI support time synchronization).

Machine Control

These systems require coordinated measurements and actions using a control network. Control networks need to accept inputs from sensors, perform control loop processing, and initiate actions in response.  Such actions (for example controlling a networked industrial machine or a conveyor belt) are highly time-sensitive. They require deterministic network delays with low-jitter input and output sampling, to create a control system that behaves predictably. Historically they have used proprietary fieldbuses, but this had technical and business limitations, especially related to scalability, bandwidth, vendor neutrality, and flexibility.  Time synchronization for IO and event correlation is fully supported in all our offering on TSN (all TSN products from NI support time synchronization), deterministic control is supported on our CompactRIO and Industrial Controller products today.

Hardware in the Loop (HIL)

Hardware in the Loop can be viewed as a mix of a control application and a test cell. They frequently require distributed closed loop control as well as tightly synchronized measurements.

Automotive Networks

Auto makers are migrating in-vehicle busses to Ethernet to provide higher bandwidth and faster response. This started with Ethernet for infotainment (using AVB – first generation TSN).  This largely was targeted to replace MOST.  Now automakers are moving to use Ethernet (with TSN) for connection of the vehicle ECUs.  The bandwidth is needed to support ADAS operations.  This enables functions that were not possible with previous technologies, however it will replace FlexRay and co-exist with CAN/LIN.  The convergence of multiple types of data (control, infotainment, etc.) is important in an environment such as a vehicle, where auto makers would like to be able to use a single network infrastructure for all communications – such as climate control, infotainment, body electronics or driver assistance. NI is monitoring this development to influence our product roadmap to support automotive test and RCP applications.

Media Networking

While not a target application for NI products, this is a market application adopting TSN. Networks that convey audio and video information need to stick to strict timing rules. If an audio or video packet arrives late to its destination, the receiving device (for instance a video screen or speaker) has no data to present.  In practice this might mean a dropped frame of video, an unwanted audio artifact such as a pop or silence.  Moreover, such networks require predictable latencies, enabling audio data to be presented from different speakers with a known phase relationship, and synchronization between video and related audio streams (i.e. lip-sync).

 

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3. Is TSN Ready for my Application?

While the key standards for TSN are complete, the development of the tools to make TSN easy to use are still in development from both NI and from key partners.  Therefore, TSN's readiness for an application depends on the application.

Yes - if your application needs synchronization of C Series Modules across multiple locations.  The latest CompactDAQ chassis and FieldDAQ devices can provide simple and reliable synchronization of measurements. The integrated switch makes network installation and configuration automatic for may systems. Some application examples in this space are high channel count DAQ, large scale component test, structural test, and remote logging.

Maybe - If you need synchronization and deterministic communication (normally a control application).  TSN products from NI and key partners like Cisco are new.  While they are reliable and can be deployed, the network set-up is still complex and we are still adding features and platform support.  Additionally, the ecosystem of third party devices and actuators on TSN is still developing.  You should consider TSN for applications like:

  1. Long-term standardization – If you are making decisions about a long-term standardization effort, you should investigate TSN.  As a standard component to Ethernet, TSN is experiencing rapid adoption and will become a standard feature throughout the industry.  We recommend anyone working on communications standardization should look at how TSN capabilities could benefit the design.
  2. Future-proof solution – As part of standard Ethernet, all TSN products are superset of the previous generation.  This includes the synchronized CompactDAQ chassis, TSN-enabled CompactRIO controllers which are drop in replacements for the cRIO-9035 and cRIO-9039 and all Industrial controller (IC-317x) . All can be used without TSN features enabled if you choose but can provide these capabilities in future application updates.

    Note: That the cRIO-9035/9039 with synchronization require LabVIEW 2016 or later and the LabVIEW FPGA application will need to be recompiled.
  3. Challenging multiple-controller applications – Traditional fieldbusses were not designed to support multiple controllers communicating in a deterministic fashion and trying to use fieldbusses or reflective memory can be technically difficult and expensive. TSN, as part of standard Ethernet, is far more flexible and can ideally support controller to controller communications.

NI is continuing to invest in traditional offerings like EtherCAT to serve applications and we will continue to support these technologies even after TSN achieves the ease of use and ecosystem to replace these legacy technologies.

 

Figure 2. CompactRIO with NI-DAQmx and the cDAQ-9185/9189 are used with IEEE 802.1AS compliant networks.

 

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4. What Are the Benefits of TSN vs. Existing Methods? 

Improvements to standard Ethernet through support of Time Sensitive Networking will provide new capabilities that will benefit industrial applications:

  1. Open standard through the IEEE 802: this assures vendor neutrality and continued investment by silicon and infrastructure vendors.
  2. Convergence: The Industrial IoT requires that any part of a distributed system can access data. Since much of an IIoT system exists within IT (servers and the cloud), this creates the need for a converged, synchronized network on unified buses. With existing networks using disparate buses, it is difficult to get data to the IT systems in a flexible, scalable way.  
  3. Improved Asset Utilization: production uptime can be increased through more complete system monitoring coverage and real-time delivery of systems status and events.
  4. Reduced Implementation Costs: TSN promises to reduce implementation costs and to simplify network infrastructure. One reason for this is that Ethernet is used so broadly in numerous different markets.  This assures silicon availability over the long term, continued technology updates, and amortized development costs.   
  5. Reduced Development Lifecycle: Higher system composability provides the ability to more easily upgrade subcomponents while retaining existing sub-systems.
  6. Increased Flexibility: The ability to integrate new features and functions to augment existing systems.
  7. Enhanced Security: Historically control networks had little to no built-in security. This creates a large vulnerability as has been demonstrated in high publicity cases such as Stuxnet and in-vehicle hacking.  Because TSN uses standard Ethernet, the security mechanisms already deployed in IT networks can be applied to control networks with TSN.

 

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5. How Is TSN Different from IEEE 1588?

IEEE 1588 focuses on time synchronization.  It is not part of the Ethernet specification but is a separate standard.  The IEEE 1588 standard provides sets of options.  There are multiple profiles in 1588 where each profile selects which options it will use.  This impacts what hardware and software is needed to support the profile and causes incompatibilities between profiles.  As example the profile used by LXI is different than the profile used by Siemens, which is different than the one used by the power industry, which is different than the one used by telecom.  Support for each of these profiles requires different network switches and different end devices.

TSN is a series of features being added to the Ethernet standards (IEEE 802).  This includes:
• Mechanisms for time synchronization (IEEE 802.1AS)
• Mechanisms for using coordinated time to schedule traffic (IEEE 802.1 Qbv)
• Mechanisms to assure simple/scalable system configuration (IEEE 802.1 Qcc)

When the IEEE 802 group was deciding how to provide time synchronization they elected to use 1588.  However, they needed to select and standardize one profile so that silicon and other standards could properly build on the time provided.  At the time this effort started, the IEEE 1588 group was not actively meeting.  IEEE 802 selected a profile and added it to their standards work directly to assure appropriate investment and control.  This is the IEEE 802.1AS standard.

Today the IEEE 1588 group is again active and the IEEE 802 group has been working closely to align.  IEEE 802.1AS is now a profile of 1588.  It is the profile that will be used for TSN and has some performance and scalability benefits over other profiles.  We believe over time that 802.1AS will become the dominant profile in industry.

NI participates actively in both the IEEE 802 group and the IEEE 1588 group.

Currently, in addition to support for the TSN profile, NI supports 1588 V2 default profile with end-to-end synchronization on all our RT targets and on select timing/synch PXI cards.  Starting in 2017 NI offers the ability to “bridge” between the different 1588 profiles on our Industrial Controller (317x) products.  This can allow synchronization of devices that need 1588 V2 default profile and TSN networks using 802.1AS profile.  As a common example, we can synchronize a GigE Vision camera connected on one of the ports on the controller to the TSN network providing tightly synchronized vision/motion applications.

 

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6. How Are Other Organizations Planning to Use TSN?

Every major industrial vendor is contributing and planning for options on how to utilize TSN.  Some of these members are participating directly in IEEE (NI, Siemens, Rockwell Automation, GE).  Others are participating on Avnu (NI, Rockwell, Bosch Rexroth, GE, Mitsubishi, Schneider Electric).  Others are participating on IIC (NI, Bosch, Schneider, B&R).  Still others are participating in OPC-UA (NI, Rockwell, Bosch, Siemens, GE, Schneider, B&R, Beckhoff).

Many of these vendors are becoming more open about their plans with public announcements from most of the major industrial protocol organizations about active exploration or communicated plans.  This has led to announcements from the major protocol organizations including OPC Foundation (OPC-UA) and PNO (ProfiNet).

 

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7. How Is NI Working with Other Companies on TSN?

There are multiple ways that NI cooperates with other companies on TSN.  IEEE-802 defines and writes the standards for TSN. The Avnu Alliance is a non-profit consortium that defines usage models and performs conformance testing.  Public members of the Avnu consortium include NI, Cisco, Intel, Marvell, Hirshmann, Rockwell Automation, Kollmorgen, GE, Schneider Electric, Bosch Rexroth, and others.  NI also takes part in activities with groups such as the Industrial Internet Consortium, where companies work together to create proof-of-concepts and test-beds to vet the technology and provide reference architectures on how systems can take advantage of the technology.

 

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8. Next Steps

 

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