Ethernet physical layer cost savings muted
The continued need for industrial ruggedness and intelligent implementation somewhat offsets cost savings derived from sharing common Ethernet hardware and a broad-based skill base, said automation consultant ARC Advisory Group.
Plant floor networks must physically and logically isolate from enterprise network activity in order to prevent production disruptions or safety hazards. The full-duplex switched installations required for deterministic operation result in a hub-and-spoke network topology that eliminates the wiring savings of a traditional bus topology.
This is a particular trade-off at the I/O level, where the multidrop topology found in today's device networks provides appreciable wiring cost savings. The move to Ethernet on the plant floor also implies a move to dynamic host configuration protocol, bootstrap protocol, and proper management of IP addresses as well as the associated costly engineering skill set.
Ethernet implementers must be well versed in technology such as switches, routers, and firewalls, as well as management of active components.
Connectors are also an issue. The RJ-45 connector of the office world can't meet all the demands of industrial applications, so several standards are currently moving toward specification of a more industrially hardened connector.
Redundancy requirements further drive up the cost and complexity of industrial Ethernet networks, including the need for some customers to install redundant power supplies for active Ethernet switches.