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

**URL:** <https://forum.inductiveautomation.com/t/ignition-opc-ua-ethernet-ip-implementation-does-it-use-publish-subscribe-for-tags/42103>\
**Category:** Ignition\
**Created:** [January 10, 2021, 11:32pm UTC](https://forum.inductiveautomation.com/t/ignition-opc-ua-ethernet-ip-implementation-does-it-use-publish-subscribe-for-tags/42103 "2021-01-10T23:32:17Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![mudbay](https://avatars.discourse-cdn.com/v4/letter/m/a4c791/32.png) [@mudbay](https://forum.inductiveautomation.com/u/mudbay)\
**Post date:** [January 10, 2021, 11:32pm UTC](https://forum.inductiveautomation.com/t/ignition-opc-ua-ethernet-ip-implementation-does-it-use-publish-subscribe-for-tags/42103/1 "2021-01-10T23:32:17Z")

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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.

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**Author:** ![Matrix\_Engineering](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/matrix_engineering/32/19781_2.png) [@Matrix\_Engineering](https://forum.inductiveautomation.com/u/Matrix_Engineering)\
**Post date:** [January 10, 2021, 11:41pm UTC](https://forum.inductiveautomation.com/t/ignition-opc-ua-ethernet-ip-implementation-does-it-use-publish-subscribe-for-tags/42103/2 "2021-01-10T23:41:01Z")

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@Kevin.Herron @pturmel

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [January 11, 2021, 12:22am UTC](https://forum.inductiveautomation.com/t/ignition-opc-ua-ethernet-ip-implementation-does-it-use-publish-subscribe-for-tags/42103/3 "2021-01-11T00:22:33Z")

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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](https://inductiveautomation.com/moduleshowcase/module/automation-professionals-llc-ethernetip-class-1-communications) supports UDP communications for I/O and for Producer/Consumer Tags. Where “third-party” == _ **Me** _. (:

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**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [January 11, 2021, 12:44am UTC](https://forum.inductiveautomation.com/t/ignition-opc-ua-ethernet-ip-implementation-does-it-use-publish-subscribe-for-tags/42103/4 "2021-01-11T00:44:07Z")

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All of Ignition’s Logix drivers use class 3 explicit messaging to poll via the tag services defined in [1756-pm020](https://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm020_-en-p.pdf#page18).

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**Author:** ![mudbay](https://avatars.discourse-cdn.com/v4/letter/m/a4c791/32.png) [@mudbay](https://forum.inductiveautomation.com/u/mudbay)\
**Post date:** [January 12, 2021, 7:34pm UTC](https://forum.inductiveautomation.com/t/ignition-opc-ua-ethernet-ip-implementation-does-it-use-publish-subscribe-for-tags/42103/5 "2021-01-12T19:34:57Z")

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