Taking a deep dive into gigabit Ethernet

18 March 2019

It is becoming apparent that the reluctance to move beyond 100Mbit Ethernet technology is a very real limiting factor for Industry 4.0 adoption. John Browett, general manager at CC-Link Partner Association (CLPA) Europe, argues that the transition to gigabit Ethernet networking technologies has to start now.

We have already seen what the future of manufacturing will look like thanks to the picture painted by Industry 4.0. It’s a future that will be built on lots of data. Making the best use of this data without its volume crippling the systems that we are using to derive value from it, will depend both on speed and bandwidth.

Talking bandwidth
Factory networks have already evolved from simple fieldbus networks for sensors and actuators all the way to employing Ethernet right down at field level. Now we are seeing the convergence of information technology (IT) networks and operational technology (OT) networks. In many ways it is the seamless flow of information between these two worlds that defines the possibilities of Industry 4.0. 

The thing that we can be sure of is that whatever bandwidth we believe to be adequate for today's requirements, in the future we are going to need more of it. This is one of the reasons behind CLPA's focus on open, gigabit industrial Ethernet, and its argument that industry must begin the transition to gigabit if it is to reap the benefits of Industry 4.0.

There are those who argue that the speed and bandwidth debate is irrelevant, and that with the adoption of technologies such as OPC UA and TSN, bandwidth is just something we'll be able to take for granted. But while they have an important role to play, they are complementary technologies, not replacements for existing networking protocols. 

We may not know exactly what these future network infrastructures will look like, but we can already see some clues in cloud computing. The information throughput in most of today's industrial processes is some way off being regarded as 'big data', but it's a lot of information nonetheless. Right now, the information being sent to the cloud is, by and large, information for historical logging and trend analysis, separated from the real time control data by using the likes of edge computing platforms. But if the predictions of some companies are correct, then edge computing is just an intermediate step, and we could soon see the likes of virtual PLCs and virtual SCADA in the cloud, collecting data from and sending it to plant floor devices in real time.

If that picture of the future comes to pass, it will certainly need high speed networking technologies as a prerequisite. But even today, looking at the data we are trying to pour through our edge computing platforms, the standard 100Mbit technologies are surely feeling the strain.

Imagine a network that is transmitting both synchronous control information (I/O states, data registers, etc.) and asynchronous information such as alarms, quality data and other messages. A machine jam or a parameter drifting out of tolerance or any number of process glitches could see the network flooded with alarm messages, which can quickly impact on the performance of the whole system.

Speed matters
Detractors of gigabit Ethernet ask if the speed of transmission matters. It does, because it allows for more messages per cycle and thus more useful data collected. Even with a limit on the amount of data per device, this does not imply a limit on the data collected because data registers can be constantly changing. Hence as Industry 4.0 requires us to extract more useful information from production systems, gigabit Ethernet offers the ability to provide the speed and bandwidth to do this.

Not only does CC-Link IE Field have 1Gbit transmission speed, it also has a greater Network Data capacity than both TCP/IP and UDP/IP General Purpose Ethernet. These additional headers used for General Purpose Ethernet frames are placed within the Payload portion of the frame.

This necessary additional information used by those headers reduces the Network Data that can be transmitted by each Ethernet frame. In CC Link IE Field transmissions, no additional Ethernet headers are required, so network data is not reduced.

For those who still need convincing that we are heading towards a gigabit Ethernet future, it is interesting to consider the companies making industrial Ethernet switches: looking at their product portfolios reveals that you can already see growing numbers of gigabit Ethernet products. If we are to realise the goals of Industry 4.0, then we have to conclude that gigabit Ethernet isn't simply a conceptual future; it's a very real present.

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