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

Industrial Ethernet 37-9
Tcnet [21] is supported and used by Toshiba, e.g., in the transmission module of the Toshiba 3000.
It is a master/slave protocol, with a prioritization of messages. Each slave sends the messages to the master
in an available time period (time slot). Messages with lower priority use TCP/IP and those of medium
and high priorities use EPL.
Vnet/IP [22] is supported by Yokogawa. This would work with HTTP protocol over TCP/IP. There are
real-time extensions and safety extensions, Reliable Datagram Protocol (RTP). No more information is
freely available about this protocol and its extensions.
PNET on IP [23], originally developed by a Danish company (Process Data Aps), is supported by the
International P-NET User Organization (IPUO). This would be the translation of the P-NET protocol on
Ethernet UDP/IP. The structure of the messages remains the same as for P-NET over RS-485.
37.4 Features of Major Industrial Ethernet Solutions
The different Industrial Ethernet solutions are so different because they address different problems. For
instance, there is no quick and easy solution that can ensure hard real-time communication (100.μs) based
on nondeterministic protocols and COTS devices. Here are seven features, not necessarily independent,
that could help choosing an Industrial Ethernet solution compliant to different application requirements:
The category of the solution, in the sense of Section 37.2.3
The real-time capability
The compliance to communication standards
The determinism of medium access and transport layer
The QoS mechanisms available
The common transmission time
The designated application domain
The features of six major Industrial Ethernet solutions are synthesized and compared in the following
table (Table 37.2).
37.5 Synthesis
Under the promise of interoperability, “Industrial Ethernet” refers to many different solutions that are
mostly adapted from fieldbuses protocols to be used over Ethernet links. Even for nonspecific solutions
(e.g., non-hard real-time), they are not interoperable but can possibly coexist on the same network.
On the one hand, the choice of an Industrial Ethernet is then not trivial and can be linked to an
automation supplier, as was the case when using fieldbuses.
On the other hand, solutions adapted for many different types of systems now exist. However, it is
compulsory to well define the requirements of the system and to traduce them into network features
before, to be able to choose the best solution.
Abbreviations
CIP Common Industrial Protocol
COTS Commercial Off the Shelf
CSMA/CD Carrier Sense Multiple Access/Collision Detection (IEEE 802.3)
DTM Device Type Manager
EDDL Electronic Device Description Language
EPL Ethernet PowerLink
FF
Fieldbus Foundation
FF HSE Fieldbus Foundation High-Speed Ethernet
I&C Instrumentation and Control
© 2011 by Taylor and Francis Group, LLC