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The rise of industrial Ethernet

01 February 2008

As Ethernet develops it is becoming increasingly attractive to industry and, according to experts, will continue to grow in popularity for many years to come.

Figure 1
Figure 1

Industrial Ethernet experts gathered, late last year, to educate industry about the technology behind the fast growing network choice, set to be worth $940 million by 2009* , and its uses.

The Brands Hatch Thistle Hotel, Dartford, hosted representatives from CLPA, GarrettCom Europe and Mitsubishi Electric who covered the ‘what, how and why’ of industrial Ethernet.

Steve Jones, general manager of the CC-Link Partner Association kicked off the discussion with an introduction to Ethernet, starting with its development by the Xerox group in the 1970’s.

‘Industrial Ethernet, in essence, is the use of Ethernet as the data link protocol in the OSI seven layer model (see figure 1), with a fieldbus protocol as the application layer,’ he said. ‘This is conceptually similar to the various fieldbus options that are actually the use of RS232/485 as the data link layer, with the fieldbus protocol itself at the application layer.’

‘The biggest advantage, aside from cost, is the significantly greater interoperability between devices offered by industrial Ethernet,’ added Jones. ‘In particular, there is the potential for a seamless flow of data from field devices all the way up to higher level business systems and back, delivering huge gains in flexibility for manufacturers looking to boost their productivity to the max.’

Product manager for Mitsubishi Electric Europe’s Modular PLC Systems, Stefan Knauf, reiterated Jones’ argument and said Ethernet offered ‘One seamless solution from management level to sensor level’. Knauf went on to claim this aspect of Ethernet would be the ‘most important for the future’.

There is potential for a ‘single, standard network for information, configuration, control, safety, synchronisation and real-time distributed motion,’ said Jones.

‘Whilst Ethernet is not new to automation - it has been deployed since the 1990s in non-real time applications - recent developments have extended coverage to real time applications,’ added Dave Cook, technical focus group, GarrettCom Europe. Cook pinpointed the developments as Gigabit speed, a move from hubs to switches and redundant ring technology.

It is the evolution of Ethernet technology from a 10Mbps bus/tree topology to a gigabit, switch-based topology that has allowed Ethernet to support time-critical applications in industrial networks. This switch-based topology makes the implementation of an industrial Ethernet network very different from implementing a device-level network.

The infrastructure of Layer 2 and Layer 3 switches is the core of the industrial Ethernet network, providing the determinism and throughput required for control applications. The switch’s ability to eliminate collisions is the most important mechanism to provide real-time capability for Ethernet-based control systems. Switches can be added to split the data load between segments, resulting in higher performance. In addition, managed switches can prioritise traffic, allowing the preferential handling of real-time traffic over supervisory traffic.

Cook explained how switches provided determinism and Jones highlighted the importance: ‘If you send a message you want to know that it has been received.’

The Ethernet switch also makes it possible to build into the industrial Ethernet network something which was very difficult and/or expensive to do with standard fieldbus networks: and that is redundancy.

In addition, recent hardware developments have removed the communications distance limitations that have been a recognised issue with the move to gigabit Ethernet, giving users a simple upgrade path to the increased performance afforded by this high-speed technology.

A new GarrettCom switch will allow industrial installations with multi-mode fibre achieve lengths of connectivity previously only available with single-mode fibre cable, according to Cook.

‘While transmission distances of 2000m over multi-mode fibre are standard for 10/100Mb Ethernet,’ said Cook, ‘any upgrade to gigabit speed has always been a problem because the distance has been limited to just 550m.

‘Users looking to upgrade have been forced to rework their network installations around shorter transmission distances and/or single-mode topologies, implying significant time and expense. With the introduction of CSG14 converter switches GarretCom Europe has overcome these problems, and made the upgrade path simple and cost-effective.’

Along with enterprise wide connectivity, industrial Ethernet brings with it the possibility for connectivity to the plant over the internet.

‘This allows plant performance to be viewed remotely, production planning to be centralised across manufacturing sites that could be continents apart, and faults to be diagnosed remotely and in real-time in plants that could potentially be thousands of miles away,’ added Knauf.

The one over-riding theme that emerged from the discussion was industrial Ethernet offered manufacturers a single network architecture to meet the needs of all enterprise levels. Industrial Ethernet can unite a company’s administrative, control-level, and device-level networks over single network infrastructure. As David Moss, business development manager of GarretCom, said, ‘There is only one Ethernet’.

* Source: ARC, market research analysts

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