wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

37-4 Industrial Communication Systems
Safety (cf. Chapter 21)
The IEC 61784-3 standard specifies dedicated profiles for safety. Presently, only two Industrial
Ethernet solutions have a profile in this standard, EtherNet/IP (CIP Safety) and ProfiNet IO
(ProfiSafe). Other Industrial Ethernet solutions propose a safety profile but not a standardized
one, such as “safety over EtherCAT.”
Cyber Security (cf. Chapter 22)
Vendors often complete their automation offer with solutions to secure the network. In particular,
for the connection between industrial and corporate domains, vendors propose firewalls with
a configuration adapted to automation technicians’ skills.
37.2.3 Classification of Industrial Ethernet Solutions
In the previous composite definition of Industrial Ethernet, it appears that there are different Industrial
Ethernet solutions. Before listing and comparing the different standardized solutions, four categories
are proposed to classify Industrial Ethernet solutions according to the technology used.
1. “Full Ethernet”
These networks use the Ethernet standard IEEE802.3. To avoid uncertainty due to collisions, all
these networks are switched and links are used in full duplex. They can also be based on standard
prioritization of data over Ethernet and the establishment of VLAN (IEEE 802.1p and IEEE 802.1Q).
However, without any management of data flows by the emitting stations (emission rate, minimum
and maximum size of frames, etc.) they can only provide statistical guaranties of service.
Advantage: The use of COTS network devices can coexist with other Industrial Ethernet solutions
and with standard Ethernet stations.
Drawback: No guarantee of deterministic services
Examples: Modbus/TCP, Ethernet/IP, ProfiNet IO RT, FF HSE (Fieldbus Foundation High-Speed
Ethernet)
2. “Ethernet compatible” but using specific devices
To guarantee hard real-time performances, these kinds of solutions usually implement proprietary
management of traffic inside switches based on time slicing. Hence, it is mandatory to use
only specific network devices.
Advantage: Can coexist with standard Ethernet stations; can provide deterministic guaranties
Drawback: Uses specific network devices
Example: ProfiNet IO IRT
3. Implemented on common Ethernet devices
These networks can be used with standard Ethernet hardware. They use standard layers defined
in 802.3. Upper layers are modified in order to manage the network traffic, so that guaranteed
services can be provided. Thus, it is not possible to connect a standard Ethernet station directly
to the network since it would not implement the layers managing the communications on the
bus. A gateway is generally offered to provide connectivity to standard Ethernet LANs.
Advantage: Uses COTS network devices; can provide deterministic guaranties
Drawback: Uses specific NICs or requires specific communication management layers and cannot
coexist with other Industrial Ethernet or standard Ethernet stations
Example: Ethernet Powerlink
4. New fieldbuses using Ethernet links
These networks define a MAC layer different from Ethernet to provide real-time capabilities. They
require the use of specific devices. These are the latest generation fieldbuses, often providing better
performances than those of other networks. They usually provide, as did classical fieldbuses,
an acyclic traffic service that enables encapsulating other flows, such as Internet flow (http, etc.),
by means of gateways.
© 2011 by Taylor and Francis Group, LLC