Ignition OPC UA - Ethernet/IP Implementation - Does it use Publish/Subscribe for Tags?

Can anyone tell me whether Ignition’s built in OPC UA connector that support Ethernet/IP with ControlLogix controllers uses Publish/Subcription (UDP) in the back end when communicating to the controller to get Tags for Ignition or does it use Explicit messaging (TCP) to “poll” and collect data from the PLC?

My assumption at the moment is that it uses the Publish/Subscribe method for data transmission, but would like to confirm with the community.

@Kevin.Herron @pturmel

Ignition’s native Logix driver is a polling driver for named tags, following the Data Access document Rockwell publishes. The third-party “Class 1” Ethernet/IP driver supports UDP communications for I/O and for Producer/Consumer Tags. Where “third-party” == Me. (:


All of Ignition’s Logix drivers use class 3 explicit messaging to poll via the tag services defined in 1756-pm020.

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Thanks Pturmel and Kevin for the information! Much appreciated and good to know.