Certain motion devices (and other UAFX devices) will have diverging capabilities for ETH, UDP and MQTT-based PubSub communication. Examples: different sets of available Input and Output Data, different possible cycle times etc.

Forcing the vendor to provide the same capabilities for all protocols will increase the complexity of the devices and the related costs for development and testing (e.g. timing related tests). E.g. a Motion device might want to offer specific control mods only via ETH and others with a more relaxed timing also via UDP. MQTT might only be used for supervision and not for any controlling task.

Adding protocol information to the Publisher and Subscriber capabilities might be necessary to express these different capabilities within one FE.

There is concern that this would end up in too many different device variants. OPC UA Profiles could be used to make sure, that devices provide the same set of data (at least for ETH and UDP). But they would allow certain devices with very specific modes to only provide these functions via a specific protocol only.