Drives and Controls Magazine

Device-level Ethernet rings make networking easier for OEMs

07 October, 2009

Rockwell Automation is embedding an Ethernet-based device-level ring (DLR) technology into many of its control and motion products, making it easier for machine-builders to implement fast, flexible, low-cost networks for real-time EtherNet/IP applications.

Rockwell is incorporating the technology into its Allen-Bradley ControlLogix controllers, I/O systems and Kinetix motion systems. It is also releasing a standalone communication module that can connect devices not equipped with DLR technology to a ring.

In addition, ODVA has extended its EtherNet/IP specification to include the DLR protocol, paving the way for multivendor EtherNet/IP networks based on DLR.

The technology uses switch functions embedded into automation end-devices such as I/O modules and PACs (programmable automation controllers) to enable Ethernet ring network topologies at the device level. Unlike network- or switch-level ring topologies that provide resilience to the network infrastructure, DLR technology adds device-level network resilience to optimise machine operation.

When a DLR detects a break in the ring, it provides alternate routing for the data to help recover the network rapidly. Diagnostics built into DLR-enabled products identify the point of failure, helping to speed maintenance and reduce mean-time-to-repair. 

“Functional tests show that the typical recovery time for a 50-node device-level ring is less than 3ms,” says Mike Hannah, manager of Rockwell’s networks business. “With this fast recovery, most failures become invisible to devices on the network, and machines often continue operating without interruptions. Keeping production running on the plant floor helps to increase machine uptime and productivity.”

In addition to helping networks to recover, the DLR technology also simplifies network architecture while providing the flexibility to connect and co-exist with other network topologies. Multiport EtherNet/IP devices equipped with DLR technology can connect directly to neighbouring nodes and form a ring topology at the end-devices. The technology reduces the need for external components and cabling, making design and installation easier for machine-builders.

By complying with a single ring specification, manufacturers using DLR-enabled products can achieve interoperability and take advantage of the benefits provided by EtherNet/IP networks. DLR also supports the IEEE 1588 standard for precise time synchronisation and standardised Quality of Service (QoS) mechanisms to help prioritise data transmission.