In manufacturing, we already have an idea of what the future will look like. The blueprint has been provided by the future project Industry 4.0, and we know that this future will be built on data - large amounts of data. The optimal use of 'big data' requires speed and bandwidth so that the evaluation systems we use to generate value can cope with the volumes of data.

Core topic bandwidth

It wasn't so long ago that downloading even low-resolution photos over the Internet connection was a test of patience; watching movies and television over the Internet - something we take for granted today - still seemed a long way off.

The same development can be seen in factory networks, which have evolved from simple fieldbus networks for sensors and actuators to the universal use of Ethernet right down to the field level. We are now seeing the convergence of IT and OT networks. In many ways, it is the seamless flow of information between these two worlds that defines the possibilities of Industry 4.0. If the trend continues, in the foreseeable future we will have services available to us in manufacturing that we can only dream of today.

One thing is certain: in future, this will require considerably more bandwidth than is considered sufficient for today's requirements. This is one of the reasons why the CLPA is backing open Gigabit Ethernet. The industry would do well to tackle the transition to gigabit bandwidths as quickly as possible if it wants to reap the benefits of Industry 4.0.

Edge computing - an intermediate step

It is sometimes argued that the speed and bandwidth debate is irrelevant and that we can take bandwidth for granted with the proliferation of technologies such as OPC UA and TSN. There is no doubt that these are important developments, but they are complementary technologies and not replacements for existing network protocols. Network bandwidth for industrial applications is a topic we need to talk about now if we want to prepare for the reality of the factories of the future.

Although it is not yet clear what these future network infrastructures will look like, some conclusions can be drawn from the development of cloud computing. In most industrial processes, information throughput is currently still a long way from 'big data', but we are already dealing with large volumes of data. The data sent to the cloud is still mainly information for historical logging and trend analysis, while real-time control data is processed on edge computing platforms. However, if some companies' predictions come true, edge computing is just an intermediate step and we may soon see virtual PLCs and SCADA systems in the cloud, collecting data in real time and monitoring and controlling plant and machinery on the factory floor.

If this future scenario becomes a reality, high-speed networking technologies will be essential. - With the amount of data already flowing through our edge computing platforms today, conventional 100 Mbit technologies are already approaching their limits. If future networks have to transmit both synchronous control data - I/O states, data registers - and asynchronous information such as alarms and quality data, a blocked machine, a wandering parameter value or any other process disturbance can lead to the entire network being flooded with alarm messages, which can quickly affect the performance of the entire system.

A capacity analysis

But how much additional capacity does a gigabit bandwidth offer exactly? In principle, the throughput of 1 Gbit Ethernet is 10 times greater than that of 100 Mbit Ethernet, but data packetization also plays a role: The Ethernet frame format, frame type II, is basically made up of:

Preamble (8 bytes), Pause (Inter Frame Gap - 12 bytes), MAC Receiver (6 bytes), MAC Sender (6 bytes), Protocol Type (2 bytes), CRC (4 bytes) and the user data (Payload - minimum 46 bytes, maximum 1500 bytes), which includes network data and additional Ethernet headers.

This results in a frame size of at least 84 bytes and a maximum of 1538 bytes. Network data is the information in the payload part of the frame. For some Ethernet applications, additional overhead is required and part of the payload, which reduces the size of the network data. Without additional Ethernet overhead, payload and network data are the same.

Payload with the minimum of 46 bytes and frame format Ethernet II (no additional overhead):

• Gigabit Ethernet has a throughput of 1,488,095 frames/s and can transmit a maximum of 68,452,370 network data bytes in one second.
• 100 Mbit Ethernet has a throughput of 148,809 frames/s and can transfer a maximum of 6,845,214 network data bytes in one second.

Payload with a maximum of 1500 bytes and frame format Ethernet II (no further overhead):

• Gigabit Ethernet has a throughput of 81,274 frames/s and can transfer a maximum of 121,911,000 network data bytes in one second.
• 100 Mbit Ethernet has a throughput of 8127 frames/s and can transfer a maximum of 12,190,500 network data bytes in one second.

Devices in Gigabit Ethernet networks can therefore send more messages. As each message in the network takes less time, more messages can be sent without overloading the network.

This is not about collision problems, as there are generally other strategies for this in industrial Ethernet networks. It is more about how much useful data can be captured and used from each message. All of this has an impact on the quality of production decisions made at the enterprise level.

It's all about speed

Critics of Gigabit Ethernet doubt that the speed of transmission plays a role. It is obvious that with higher transmission speeds, more messages can be transmitted per unit of time and therefore more valuable data can be collected. Even if the amount of data per device is limited, this does not limit the data collected, as the data registers can change constantly.

Industry 4.0 demands that we extract more and more useful information from our production systems. Gigabit Ethernet can provide the necessary speed and bandwidth for this.

Author:
John Browett is General Manager of CLPA Europe.

The special feature of CC-Link

CC-Link IE Field not only has a transmission speed of 1 Gbit/s, but also a higher network data capacity than TCP/IP and UDP/IP General Purpose Ethernet. This is due to the additional overhead for the IP, TCP and UDP headers used by the General Purpose Ethernet frames. These additional headers for General Purpose Ethernet frames are placed within the payload portion of the frame, thus reducing the network data that can be transmitted with each Ethernet frame. Transmissions via CC Link IE Field do not require additional Ethernet headers, so that the entire payload is available for network data.

Data for comparison:

The payload for an Ethernet frame is 46 - 1500 bytes/transmission

• 1 Gbit Ethernet with a minimum payload transmits 1,488,095 frames/s
• 1-Gbit Ethernet with a maximum payload transmits 81,274 frames/s

C-Link IE field:
No additional Ethernet headers are required.
With a payload of 46 bytes, 46 bytes of network data can be transmitted.

• Transmission of 68,452,370 bytes of network data per second.

With a payload of 1500 bytes, 1500 bytes of network data can be transferred.

• Transmission of 121,911,000 bytes of network data per second.

TCP/IP:
The IP header requires 20 bytes and the TCP header 20 bytes.
With a payload of 46 bytes, 6 bytes of network data can be transferred.

• Transmission of 8,928,570 bytes of network data per second.

With a payload of 1500 bytes, 1460 bytes of network data can be transferred.

• Transmission of 118,660,040 bytes of network data per second

UDP/IP:
The IP header requires 20 bytes and the UDP header 8 bytes.
With a payload of 46 bytes, 18 bytes of network data can be transferred.

• Transmission of 26,785,710 bytes of network data per second

With a payload of 1500 bytes, 1472 bytes of network data can be transferred.

• Transmission of 119,635,328 bytes of network data per second.

Compared to conventional Ethernet networks, CC-Link IE Field therefore offers a performance increase of over 660% more bytes per second than TCP/IP at Gigabit speed and over 150% more than UDP/IP when transmitting at the payload minimum.

Since there are currently no other open 1 Gbit general purpose Ethernet networks available, we must also compare CC-Link IE Field with other currently available industrial Ethernet networks, i.e. CC-Link IE Field compared to 100 Mbit general purpose Ethernet. Using the same calculation basis: depending on the payload, CC-Link IE Field can in principle offer a performance increase of up to 7500% more bytes per second than TCP/IP and around 2500% more than UDP/IP.