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More possibilities thanks to protocol standards

Everything is networked

Industrial communication describes the networking of machines with computers and is the basis for smart, networked production. Such networked industrial systems are also known as smart factories.

This involves establishing common communication from sensors, actuators and control elements right through to inventory management systems, which can simplify, illustrate and improve processes. Similar to the OSI reference model, this type of communication does not just take place within a network level, but across levels.

Communication between the different network participants of one or more network levels must be standardised so that devices from different manufacturers can also “understand” one another. A standardised, barrier-free language is therefore required – the solution: protocol standards.

A large number of different network protocols are used in the individual layers of the OSI reference model, which we will not elaborate on here.

Probably the most well-known protocols (which also form the basis for data exchange over the Internet) include:

  • TCP: Protocol for data exchange between network components
  • FTP: Protocol for exchanging files over the Internet
  • HTTPS: Protocol for encrypted transmission over the Internet
  • IP, IPv4 and IPv6: Protocols for address verification on the Internet
  • SMTP: Protocol for sending e-mails

Everything is secure

Communication between the various devices in the networked system takes place via the Internet or other internal LAN networks (Local Area Network). Networks of this type present both opportunities and challenges. The protocol standards take into account the following values:

  1. Integrity (data is not tampered with during transmission)
  2. Confidentiality (data is treated as confidential during transmission)
  3. Verifiability (the identity of the sender and receiver can be verified)
  4. Media-disruption-free processing (only one medium is used for data transmission)

Everything is standardised

The IEC, the International Electrotechnical Commission, has described, defined and standardised a communication standard for industrial automation in one standard: IEC 60870 or for Germany: DIN EN 60870.

The standard comprises a whole series of specifications, which have been organised into a series of standards. The series of standards covers the following topics:

  • Switchgear engineering
  • Telecontrol technology
  • Network control technology

The protocol standards are part of the field of telecontrol technology. As a result, the IEC 60870–5 series of standards is valid. The parts of the standard consider various partial aspects:

  • IEC 60870-5-1: Transmission frame formats
  • IEC 60870-5-2: Transmission procedures
  • IEC 60870-5-3: Structure of application data
  • IEC 60870-5-4: Definition and coding of information elements
  • IEC 60870-5-5: Basic application functions

The following are also relevant for the definition of protocol standards:

  • IEC 60870-5-101: Application-related standard for telecontrol tasks (serial communication)
  • IEC 60870-5-102: Basic functions for transmitting totals
  • IEC 60870–5–103: Standard for protection signal transmission and interference elimination (within a control cabinet)
  • IEC 60870-5-104: Application-related standard for telecontrol tasks in IP networks

The specifications of the standard set a universal standard, but still allow room for manoeuvre for specific applications.

Everything is organised – topologies

As a result, the various transmitters and receivers within the communication system work according to precisely defined rules to enable data to be exchanged.

To connect the various devices to one another, switches or routers that perform a distribution function in the network are required. They ensure that all network participants make logical connections.

The logical connections are defined in the network topologies . These show how the devices are arranged and connected in a network.

With point-to-point topology, there is only a simple, direct connection between two devices. Both devices can use these connections for mutual communication.
With point-to-multipoint topology, several devices are fed through a central system. Each device in the system has a common branch point in communication.
With line topology, several devices are connected to one another. A cable is laid from device to device. Each end of the line is terminated with a device.
With the bus topology, all devices are connected via a common cable. Every device has access to the signals transmitted via the cable. To prevent interference on the cable, the cable ends are fitted with a terminating resistor.
The ring topology is a closed cable route. All devices are connected to one another by a cable ring. This means that every device receives and outputs a cable.
Star topology has a central network component. This is normally a hub or switch that assumes the distribution function. Each device is connected to it via a cable.
The tree topology is an extended star topology. It enables implementation in larger networks.
Mesh topology is a decentralised network. There are no binding structures and all network nodes, i.e. all devices, are connected to one another.
The braid typology is a forward-looking development of the star typology. There is no central node; instead, the devices are redundantly connected to a structured, meshed topology.