TSN (Time Sensitive Networking): The lack of a time mechanism remains an elephant in space

 TSN (Time Sensitive Networking): The lack of a time mechanism remains an elephant in space


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  TSN (Time Sensitive Networking): Lack of Timing Mechanism Remains an Elephant in Space

By Bill Lydon, Editor, Automation.com

The trend continues to rise in anticipation of TSN's commitment to multimode communication Mainstream generally decides on computers, vehicles, industrial automation and building automation. The big missing element that continues to hamper this important development is the lack of complete time management solutions. This was a testimonial from the ODVA Industry Conference 2018 and the 19th Annual Meeting, especially a roundtable titled "Fireworks in the Aether," hosted by Harry Forbes of the ARC Advisory Groups with panelists:

  • David Brandt, Rockwell Automation / ODVA Connection to IEEE 802.3
  • Bob Voss, Panduit / ODVA, Chair of EtherNet / IP Physical Layer SIG
  • Joakim Wiberg, Industrial Networks of HMS Industrial / ODVA
  • Jordon Woods, Analog Devices Inc./ODVA connection to IEEE 802 [19659008] This session explored the emerging Ethernet technologies and standards that are expected to set the stage for significant changes in the industrial automation industry. The members of the ODVA panel believe these changes will create new market opportunities for the convergence of industrial Ethernet networks, edge devices, and accelerated migration from traditional fieldbus to industrial Ethernet. As this article discusses, the panel of experts for EtherNet / IP experts continued to share how new technologies and standards for single-pair Ethernet, time-sensitive networking, and constrained-node networks will affect Industrial Ethernet and EtherNet / IP , 19659009]

    A timeframe for true TSN remains unclear

    TSN's vision has been expressed as a common communication channel for all forms of communication, including multimedia, audio, video, data, and industrial automation networks. However, when I asked the panel if there was a solution to the creation of a common open time synchronization standard managed by an independent, open third party, it said that there would be no response from anyone in that body to this dilemma. A panelist commented, "Interesting ...". Obviously, there is no perspective to solve this central problem.

    However, there are still more problems to solve. Moderator Harry Forbes explained one as he asked the panelists about the cost of a new network infrastructure. One participant described a number of obstacles, including the costs that would have to be reduced, and the development of simple system configuration tools.

    TSN as a tightly coupled network

    While I have discussed the benefits of TSN, I have added new levels of complexity to industrial Ethernet networks where network timing is closely linked to network configuration and management.

    The Most Similar Network In my experience, the Allen-Bradley network The ControlNet TM was a tightly timed and managed network devoted to industrial control and surveillance, with these tight communications triggering high determinism , While the scope of the topic was complex, it was designed for industrial automation applications with a set of software and controllers from a single manufacturer, Allen-Bradley.

    In contrast, TSN is considered as a common common network for multimode communication for general data processing, VOIP, professional audio, video, file transfer, industrial automation, building automation and other data communications.

    Basically, industrial networks such as EtherNet / IP require a high network bandwidth in relation to the load. These networks use industry-standard Quality of Service (QoS) standards in IP-based networks according to IETF standards, network configuration options, and segmentation networks to provide adequate performance for industrial automation applications. This is not deterministic, but managing the network configuration and segmentation can achieve the performance of the automation system in most applications.

    Effects of TSN Configuration Software

    To use TSN scheduling, it appears that control software and controller firmware must be redesigned to allow the definition of I / O point and variable timing specifications. Some examples to illustrate this need:

    Example 1: An application that sends 30 data points in my PLC to 4 other PLCs to control every 10 milliseconds +/- 0.5 milliseconds maximum deviation. The application engineer would need a way to set the timing request and destination controls in the control editor, and this information must be communicated to the TSN time manager.

    Example 2: A PLC application with 500 I / O points and 2,000 register values ​​with multiple data timings. The application engineer would need a way to set the timing request and destination controls in the control editor, and this information must be communicated to the TSN time manager. Prerequisites for this example:

    • 30 data points transmitted every 10 milliseconds +/- 0.5 millisecond maximum deviation to 4 other PLCs for control.
    • 100 data points sent to 12 separate drives, 0.5 milliseconds +/- 0.01 milliseconds, maximum deviation
    • Communications compensation 100 milliseconds +/- 1.0 milliseconds Maximum Deviation

    In this example, there are three different timing streams for 2,500 records, all of which must be defined by the application engineer in the control editor and reported to the TSN time manager.

    With the goal of supporting multiple industrial network protocols and data-multimedia applications, an industry-wide network manager and API standard is required that all vendors must adhere to. However, if you ask several people for standardization in this area, it is clear that there is no openly defined standard and certainly no identified certification group.

    Bill's Thoughts & Observations

    I believe that there is good news for users as there is no compelling reason to switch to this technology until there are proven standards and standards products for the complete architecture. These include control software and control configuration software and controls.

    There are many unanswered questions about the practical application of TSN in system architecture and in application engineering for control and automation. However, there are also many demonstrations at trade events and "testbeds" that are really laboratory projects. When I ask people how they configured the network, the network is very crude.

    Several presentations and discussions with industry experts and vendors suggest that the carmaker will be a major catalyst for TSN's success in the industry. A potential use for in-vehicle communication would legitimize the technology and reduce volume-related costs. There are several technologies that compete for this position in the automotive industry, and at this time there are no clear winners.

    In the automotive industry is discussed whether a single large network in vehicles or multiple application-specific networks (ie lock brakes). Automotive applications must have stringent compliance and certifications that may improve the design of the network architecture. The issues include reliability, cyclic security, failure modes, network availability, and other important issues. Industrial automation applications face the same issues that need to be addressed before considering TSN.

    TSN standards, APIs, certifications, time management, and other elements are not yet the point at which system offerings for general data processing and industrial automation can be produced. Certainly, a deterministic unifying network seems to have a number of advantages, but one of Key to a successful TSN implementation is that TSN must be independent of applications and industrial automation protocols.

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2018-11-27 22:37:58
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