Real-time ethernet

In the field of automation technology , the trend can be observed, existing field buses of the first generation by a real time - Ethernet , Eng. Also known as Real Time Ethernet (RTE) , to replace or supplement. The goal is to create a single computer network from the control level in the office area to field devices in industrial production plants. This trend is known as the vertical integration of automation technology. A main problem is that the widespread standard Ethernet does not meet the requirements of industrial real-time, which require isochronous cycle times of less than 1 ms (e.g. for motion control applications).

Three alternative methods are used to make Ethernet real-time capable:

Modification above the TCP / IP level in the OSI model (OSI layer 5–7)
Modification above the data security layer (via OSI layer 2)
Modification of the Ethernet layer itself (OSI layer 1–2)

The further down the OSI layers the modification is made, the sooner isochronity can be achieved. This is necessary in order to meet the high real-time requirements of drive technology . The aim is to ensure the synchronicity of industrial plant parts no longer via a mechanical shaft , but instead via isochronous data frames in a real-time network. In this context one speaks of the principle of the software wave . The Precision Time Protocol has established itself for high-precision synchronization of the data frames sent .

On the other hand, modifying the Ethernet on the lower protocol levels may reduce the compatibility with the Ethernet standard.

In order to be able to withstand the increased mechanical loads such as dust, vibrations or splash water, the standard Ethernet plugs and cables are usually replaced by special Industrial Ethernet hardware.