Enable Recite

Subscribe options

Select your newsletters:

Please enter your email address:

@

Your email address will only be used for the purpose of sending you the ITER Organization publication(s) that you have requested. ITER Organization will not transfer your email address or other personal data to any other party or use it for commercial purposes.

If you change your mind, you can easily unsubscribe by clicking the unsubscribe option at the bottom of an email you've received from ITER Organization.

For more information, see our Privacy policy.

News & Media

Latest ITER Newsline

  • Art and ITER | Two sisters, two suns and a monument to fusion

    Amid the gentle slopes of Asciano, Italy, there stands a stone window that frames the Sun on the summer solstice. It looks as though it might have always been t [...]

    Read more

  • Staff | The men and women of ITER

    They hail from Ahmedabad and Prague ... from Naka and Moscow ... from Seoul, Hefei, Atlanta and hundreds of other towns and cities across the 35 nations partici [...]

    Read more

  • ITER Talks | All about ITER and fusion

    Beginning this autumn, the ITER Organization will be launching a new video series to inform, inspire and educate. The first video—introducing the series and off [...]

    Read more

  • Image of the week | A majestic components enters the stage

    The floor of the Assembly Hall is an ever-changing stage. Like characters in a grand production, components of all size and shapes make a spectacular entry, pl [...]

    Read more

  • Magnet system | A set of spares for the long journey

    In about five years, ITER will embark on a long journey through largely uncharted territory. Conditions will be harsh and—despite all the calculations, modellin [...]

    Read more

Of Interest

See archived entries

Networks

Ensuring real-time distributed computing at ITER

Many of the control systems at ITER require quick response and a high degree of determinism. If commands go out late, the state of the machine may have changed in the interim, rendering actions useless—and maybe even detrimental.

The hardware and software components delivered by ITER Member states must be able to cooperate seamlessly over the deterministic communication infrastructure. A large part of the integration work involves maintaining the communication network that guarantees the travel time of a message from one computer to another. (Click to view larger version...)
The hardware and software components delivered by ITER Member states must be able to cooperate seamlessly over the deterministic communication infrastructure. A large part of the integration work involves maintaining the communication network that guarantees the travel time of a message from one computer to another.


Dozens of computers take part in the tight control loops of measuring, processing, ordering and acting. Most of the control systems (and some other systems) at ITER depend on a platform that enables collaborative processing at the rate of around 1000 operations per second, with a guaranteed delay.

"The requirement for reaction time is 10 microseconds," says Bertrand Bauvir, Leader of the Central Control Integration Section. "We can take data in at 10,000 times per second, process it and send commands out. One challenge is to perform the necessary amount of computation on time, because some of the algorithms are fairly complex."

Off-the-shelf technology and skilled software developers

The Central Control Integration Section is responsible for the integration and verification of hardware and software components delivered by ITER Member states to guarantee that each piece is able to cooperate seamlessly over the deterministic communication infrastructure. A large part of the integration work involves maintaining the communication network that guarantees the travel time of a message from one computer to another. This guarantee must hold even for multicasting—when a message has to be replicated and sent to more than one other computer.

Fortunately, many other organizations have had similar needs—and the real-time networking required by ITER can be achieved with careful software and network design, based on well-vetted commercial-off-the-shelf Ethernet network components.

One interesting fact about potential bottlenecks on the network is that it takes more time for light to travel through the optical fibres connecting the buildings to the server room than it takes for an Ethernet switch to replicate and forward a message to multiple destinations. This is because light travels around 1.5 times slower through an optical fibre than in a vacuum, resulting in a best-case latency over optical fibre of about 5 microseconds per kilometre. By contrast, high-performance cut-through Ethernet switches can achieve sub-microsecond packet forwarding time.

Another large part of real-time distributed computing is the operating system used on each system. Most do not guarantee a response time, so ITER relies on a real-time version of Red Hat Linux that has been widely used for years.

"All contributions from the Member states have to meet our performance and latency requirements—and all software must behave in a way that does not hinder the performance of other systems connected to the real-time communication network," says Bauvir. "We set standards, starting with how to physically connect to the network and how to communicate. Suppliers have to buy the right computers and run the right operating system. They also have to use our software libraries for communication."

But even with standards and guidelines—and good software engineering in different parts of the world—the overall performance of the distributed real-time control function depends on each component collaborating seamlessly. So when a control system component is delivered, Bauvir and colleagues perform verification and commissioning, including quality assessments and functional checks.

Bertrand Bauvir is looking forward to seeing it all work. "Until now we have been integrating what we call utilities," he says. "These are control systems for monitoring and distributing electrical supply, cooling water, and so on. In the next six months we will begin to integrate and commission the first equipment that participates in the real-time control of the machine. We will be hooking up the very first real-time computers; many more will follow in the coming years."



return to the latest published articles