The FieldDAQ device features a full hardware-accelerated internal Ethernet switch for greater performance, wiring flexibility, and compatibility over standard Ethernet ports.

The Ethernet switch exposes two Ethernet ports to the user. Either port can be used to connect the device to the network. The two ports can be used to connect multiple devices in a daisy-chain topology. The switch also supports the Rapid Spanning Tree Protocol (RSTP) algorithm, enabling ring topologies. Refer to Topology Options for more details.

IEEE 802.1AS-2011 Precision Time Protocol

The internal Ethernet switch is an IEEE 802.1AS time-aware bridge, compatible with the IEEE 802.1AS-2011 Precision Time Protocol. It can synchronize local measurement signals to other devices across an IEEE 802.1AS subnet. It can also serve as a bridge, synchronizing IEEE 802.1AS devices that are attached to each of the two ports. Refer to Synchronization across a Network for more details.

IEEE 802.1Q Rapid Spanning Tree Protocol (RSTP)

It is possible to create loops in a network using the FieldDAQ device. To prevent these loops from disrupting the network, the FieldDAQ device implements the IEEE 802.1Q Rapid Spanning Tree Protocol (RSTP). Using this protocol, each FieldDAQ device can find the shortest path for incoming packets to reach the rest of the network. When multiple paths exist, this adds a form of redundancy. If a link fails, the protocol automatically switches to use the redundant link. This process can take several seconds in some cases.

To gain these benefits on external switches connected to the FieldDAQ device, IEEE 802.1Q (RSTP) must be enabled. All external switches must be configured to allow the FieldDAQ device to transmit RSTP packets, known as Bridge Protocol Data Units (BPDU). If any switch has a feature—such as “BPDU guard”—enabled, the port connected to the FieldDAQ device is disabled and communication is lost. Refer to the documentation for your external switch for information about enabling RSTP and disabling BPDU guards on the switch.

IEEE 1588-2008 Protocol

The internal Ethernet switch can be configured to act as a 1588 "boundary clock" implementing the IEEE 1588 delay request-response default PTP profile (sometimes referred to as "default profile"). When so configured, it can synchronize local measurement signals to other devices across an IP subnetwork and can serve as a bridge, synchronizing 1588 devices that are attached to each of the two ports. Refer to Synchronization Across a Network for more details.

Note The IEEE 802.1AS protocol is an IEEE 1588 profile, but is incompatible with other IEEE 1588 profiles. When FieldDAQ devices are using the IEEE 802.1AS protocol to synchronize they cannot synchronize with devices that use other protocols or IEEE 1588 profiles and vice versa.

FieldDAQ MAC Addresses

The FieldDAQ device is associated with two MAC addresses—both of which are labeled on the device—device and switch.

These MAC addresses are not associated with a particular Ethernet port, but both addresses can appear on both ports as necessary.

Table 10. NI MAX Device and Switch MAC Addresses
Device MAC Address Switch MAC Address
Associated with the device's IP address Associated with the internal Ethernet switch—not associated with the device’s IP address
Used by normal device traffic Used for Ethernet protocols for network configuration and synchronization
Listed in MAX Not listed in MAX

The switch MAC address is used to implement the following switch protocols:

  • IEEE 802.1AS-2011 (Precision Time Protocol)
  • IEEE 802.1Q (Rapid Spanning Tree Protocol [RSTP])
  • IEEE 1588 (Delay Request-Response Default Precision Time Protocol)

The switch MAC address only appears in packets exchanged between the switch embedded in the FieldDAQ device and the next Ethernet device. It will not propagate further in a properly configured network. For more information about the recommended configurations for networking the FieldDAQ device, refer to Topology Options.