Chapter 3
Hardware Overview
NI PCI-1588 User Manual
3-6
ni.com
Network Topology
To obtain the best NI PCI-1588 performance, follow these guidelines to set
up the Ethernet network topology:
•
Use short cabling when possible. Ethernet cabling is inherently
asymmetric; the longer the cabling, the higher the asymmetry. This
impacts synchronization performance, because the IEEE 1588
protocol assumes a symmetric network path.
•
Use hubs when connecting to multiple IEEE 1588-capable devices.
Hubs offer low latency and close to deterministic performance for
transporting Ethernet traffic. This latency is on the order of hundreds
of nanoseconds. Using switches degrades performance due to
increased latency and indeterminate performance from the onboard
buffers. Synchronization performance across switches can be in the
tens of microseconds. If a switch must be used, obtain a 1588 boundary
clock or transparent switch to achieve the best performance. These
devices allow traffic to cross Ethernet collision domains without the
inherent loss in performance from a switch or router.
•
Ensure that the network is running at 100 Mbps by noting the Speed
LED status. Synchronization performance is degraded when running at
10 Mbps.
Operating Environment
For best synchronization performance, the NI PCI-1588 operating
environment is as important as network topology. Follow these operating
environment guidelines, while taking care to remain within the specified
operating temperature limits:
•
Install the NI PCI-1588 in your PC as far as possible from other boards
and in a slot with the least direct airflow, while taking care not to
alter the cooling properties of your PC. In addition, be sure the
computer case is properly installed. Airflow can degrade the
NI PCI-1588 performance, because it tends to cause rapid changes in
temperature. The NI PCI-1588 has precision thermally compensated
components, but limiting direct airflow helps achieve the best
performance. Consider placing the computer containing the
NI PCI-1588 in an environment free of rapid temperature transitions.
•
Perform the same steps as above to ensure that all other
IEEE 1588-capable devices also have a thermally stable environment.
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