ABSTRACT
Ethernet is the most popular physical layer local area network (LAN) technology standardized in IEEE 802.3. Ethernet has gone through four generations over the years. The minimum and maximum payload in an Ethernet frame are 46 and 1500 bytes, respectively.
Industrial Ethernet differs from standard Ethernet in traffic prioritization, robust equipment, hardware, and industrial grade components used.
Ethernet and transmission control protocol/internetworking protocol (TCP/IP) protocols failed to satisfy real-time deterministic communication from machine control to actuators and sensors. Ethernet fieldbuses could achieve determinism and the most sought after such fieldbuses are: EtherCAT, Ethernet Powerlink, EtherNet/IP, SERCOS III, and PROFINET IRT.
EtherNet/IP offers producer-consumer services and a very efficient peer-to-peer communication between slaves. It is deterministic in nature with limited real-time capability. It is compatible with OPC Internet protocols like HTTP, SNMP, FTP, and DHCP. It uses a CSMA/CD MAC model that determines how networked devices share a common bus.
In the EtherNet/IP layer model, EtherNet and IP correspond to data link and network layers, respectively. Common industrial protocol (CIP) of EtherNet/IP corresponds to layers 5-7 of open systems interconnection (OSI).
Since the maximum payload of Ethernet frame is 155 bytes, message prioritization is asserted in EtherNet/IP protocol so that any time-critical data can achieve determinism.
