This clause defines a component model to structure the selection of functional networking features. This component model consists of Bridge Component (see 6.2), End Station Component (see 6.3), IA-station (see 6.4), and UAFX Station (see 6.5).

A Bridge Component interconnects two or more network segments and forwards packets between them. This specification supports the Bridge Component features listed in 6.2.2, including link speeds of 10 Mb/s to 10 Gb/s.

A Bridge Component may support the following features:

C-VLAN component requirements as defined in IEEE Std 802.1Q-2018, 5.5.

NOTE This specification does not make use of the Multiple VLAN Registration Protocol (MVRP).

Strict priority algorithm for transmission selection as defined in IEEE Std 802.1Q2018, on each port for each traffic class

Regenerating priority as defined in IEEE Std 802.1Q2018, 6.9.4

Frame filtering as defined in IEEE Std 802.1Q2018, 5.4.1, Item h)

Per-stream filtering and policing as defined in IEEE Std 802.1Q2018,

Enhancements for scheduled traffic as defined in IEEE Std 802.1Q2018, 5.4.1, Items ab) and ac)

NOTEFor UAFX, the enhancements for scheduled traffic mechanism relies on a synchronized Working Clock.

Frame Preemption as defined in:

IEEE Std 802.1Q2018, 5.4.1, Item ad)

IEEE Std 802.32018, Clause 99 (Interspersing Express Traffic Support), including support of the Additional Ethernet Capabilities TLV in an LLDPDU per IEEE Std 802.32018, 79.3.7

TE-MSTID as defined in IEEE Std 802.1Qcc2018, 5.5.2 Items a) and b).

An End Station Component is the source or destination of network traffic.

An End Station Component may support the following features:

Transmission and reception of C-VLAN tagged frames.

NOTEA future release of this specification will define additional End Station Component requirements.

IA-stations may be a simple End Station Component (see 6.3) acting as the source or destination for control data traffic. IA-stations may also include a Bridge Component (see 6.2). More complex IA-stations incorporating several End Station Components and Bridge Components within one device can also be found in industrial automation (e.g., a Controller with multiple modules).

Figure 10 shows examples of three IA-stations. IA-station 1 is comprised of one End Station Component, IA-station 2 is comprised of one End Station Component and one Bridge Component, and IA-station 3 is comprised of a Bridge Component and two End Station Components.


NOTEHowever, not shown in this example, it is possible for multiple End Station Components to share a single Bridge Component or a single End Station Component to share multiple Bridge Components.

Figure 10 – IA-station examples

An IA-station shall:

comprise at least one conformant End Station Component as defined in 6.3,

support topology discovery as defined in clause 7.3.

An IA-station may:

comprise one or more conformant Bridge Components as defined in 6.2,

support remote management as defined in clause 7.2,

support time synchronization as defined in clause 7.4.

Ethernet QoS mechanisms are defined to operate on PCP or traffic classes. For the latter, a mapping between the PCP value in the frame and the associated TC is needed. If the PCP to TC mapping has not been explicitly configured, an IA-station shall use the mapping defined in IEEE Std 802.1Q Table 8-5.

A UAFX Station is an IA-station (see 6.4) supporting the UAFX communication and application layer (see Figure 1). The UAFX communication and application layer is a logical component acting as a source of and/or destination for link layer data traffic. Thus, each UAFX Station incorporates at least one End Station Component where the UAFX communication and application layer can be located. Figure 11 shows that the UAFX communication and application layer can either reside in a single End Station Component (UAFX1, End Station Component 1) or in multiple End Station Components (UAFX 2, End Station Component 2, End Station Component 3).


Figure 11 – UAFX Station examples

A UAFX Station shall:

comprise a conformant IA-station,

support modelling of network interfaces and QoS in the UAFX communication and application layer:

Each physical network interface available to the UAFX Application shall be represented as an instance of IetfBaseNetworkInterfaceType in the NetworkInterfaces Folder defined in OPC 1000022. All VLAN interfaces attached to these physical network interfaces shall be represented as defined in OPC 1000022. A UAFX Station shall at least provide the default VLAN interface with the BrowseName as defined in Table 2 and a HasLowerLayerInterface reference to the respective physical network for each of these physical network interfaces. If the VlanId value has not been explicitly configured for this default VLAN interface, the VlanId shall assume the value defined in Table 2.

Table 2 – Default VLAN interface values


VlanId (default)



Note: The BrowseName of the default VLAN interface in Table 2 starts with the physical interface that this VLAN interface is associated with and ends with the interface label “uafx-vlan” separated by a dot (“.”). “<physical-interface>” in Table 2 is a placeholder for the BrowseName (e.g., “eth0”) of the associated physical interface. This composition ensures the uniqueness of the default VLAN interface BrowseName in UAFX Stations with multiple network interfaces.

A UAFX Station shall provide a PriorityMappingTable with at least the default entries for MappingUri/QosCate gory and PriorityLabel as defined in Table 3. If PCP and DSCP values have not been explicitly configured (i.e., to accommodate the needs of an existing network), PriorityValue_PCP and PriorityValue_DSCP shall assume the values defined in Table 3.

Table 3 – Default PriorityMappingEntryType values








Each physical network interface available to the UAFX Application represented by an instance of IetfBaseNetworkInterfaceType in the NetworkInterfaces Folder shall have a reference to an instance of PriorityMappingTableType that is exposed to OPC UA Clients, e.g., for adaptation during the system integration phase (see 5.2.4), as defined in OPC 1000022. The referenced PriorityMappingTableType instance shall include the AddPriorityMappingEntry and DeletePriorityMappingEntry Methods.