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

37-2 Industrial Communication Systems
This illustration
shows the maximal
segmentation.
These different
levels can be
assembled in many
different ways.
Gateway or DMZ
Gateway or DMZ
Gateway
Automation network
Corporate LAN
Industrial LAN
Level 3 : Domain
applications
Industrial LAN
supervision & control
Level 2 : local SCADA &
HMI
Level 1 : PLCs
Levels concerned
by industrial
Ethernet solutions.
Level 0 : Instrumentation
Fieldbus
Figure 37.1
Theoretical network segmentation from Corporate LAN (top) to Fieldbus (bottom).
First, a general definition of Industrial Ethernet is built, as well as a technological classification of the
solutions into four categories. Then a focus is given on standardized solutions of the IEC 61158.
Finally, a synthesis table is proposed to give the main features of each solution. Indeed, there is no
solution adapted for all problems, and industries have to be aware of both functional and technical
requirements to choose the best fitted Industrial Ethernet solution.
37.2 Industrial Ethernet
In the IT domain, Ethernet, TCP (or UDP), and IP are now the de facto standards. Most higher layer
protocols, open or proprietary, rely on those protocols for access control, network, and transport services.
Thus, higher layer communications protocols can easily coexist on the same network. Moreover,
many standard protocols over TCP/IP, for instance, FTP for file transfer or HTTP for transporting web
pages, commonly provide the necessary network services needed by applications. This is far from being
the case in the industrial networking solutions, as it is shown in the two following subsections. Section
37.2.3 then suggests a classification of “Industrial Ethernet” solutions.
37.2.1 What Does Ethernet Mean?
Ethernet is defined in the IEEE 802.3 standard. It provides most of the functions and services corresponding
to layers 1 and 2 of the OSI model (cf. Chapter 1) and is well known for its famous and convenient
medium access control method: CSMA/CD (cf. Section 2.1).
However, when associated with the adjective “industrial,” Ethernet can refer to three different exclusive
meanings. Such designation can either only use Ethernet standard products, including network
interface cards (NICs), switches, and cables; be used in a network with Ethernet standard hardware but
with specific NICs; or only use Ethernet cables, everything else being specific.
As a consequence, different Industrial Ethernet types are not interoperable and may or may not coexist
on the same network, depending on the solutions.
© 2011 by Taylor and Francis Group, LLC