UAFX defines the use of different kinds of communications. For example, the exchange of control data via OPC UA PubSub, connection establishment via OPC UA Client  Server, link-local communication, e.g., LLDP (see 7.3) and gPTP (see 7.4), and remote management with NETCONF (see 7.2). To support the UAFX system operation, these kinds of communications may demand different Quality of Service (QoS) in the network.

This subclause provides an overview of how the definitions in this document can be applied to a network containing UAFX  Stations (see 6.4.3) and other IA-stations (see 6.4) such that Connections can be handled with appropriate QoS. With this release, UAFX Stations can use Best Effort or priority-based QoS for OPC UA PubSub traffic. In addition, enhanced priority-based QoS can be achieved in the network using the TSN mechanisms selected in this document.

To decouple the QoS specification for applications created during the application engineering phase from the actual QoS configuration in a given network, Controls Engineers define the application's QoS needs in the form of abstract QoS categories and labels. Similarly, Controls Engineers can use abstract network interface names to allow the use of VLANs as needed, e.g., for priority-based QoS at the Ethernet layer. The OPC UA Communication Stack then uses a PriorityMappingTable (see OPC 1000022) to translate the abstract QoS category and label of a Connection to concrete priority values in the message. Similarly, the UA Communication Stack can use the representation of VLAN interfaces in the OPC UA Information Model to resolve abstract VLAN interface names to VLAN IDs in the transmitted packets.