and Vnet/IP (developed by Yokogawa, Iapan). In the second approach, the TCP/UDP/IP protocols
suite is bypassed, and the Ethernet functionality is accessed directly — in this case, RTE protocols use
their own protocol stack in addition to the standard IP protocol stack. The implementations in this
category include Ethernet Powerlink (EPL) (defined by Bernecker and Rainer [B8R], and now
supported by the Ethernet Powerlink Standardization Group [35]]; TCnet (a Time—Critical Control
Network) (a proposal from Toshiba); EPA (Ethernet for Plant Automation) (a Chinese
proposal); and PROFIBUS CBA (Component-Based Automation) (defined by several manufac-
turers, including Siemens, and supported by PROFIBUS International ). Finally, in the third
approach, the Ethernet mechanism and infrastructure are modified. The implementations include
SERCOS III (under development by SERCOS), EtherCAT(defined by Beckhoff and supported
by the EtherCat Technology Group ), PROFInet IO (defined by several manufacturers, including Siemens, and supported by PROPIBUS International).