Inter-Packet Gap for Ethernet Tx Is Too High When Using NI-XNET

Issue Details

I am using the PXIe-8523 and PXIe-8520 to perform Ethernet (ETH) to CAN and ETH to ETH stress testing. Ideally I need to reach the minimal Inter-Packet Gap (IPG) of 960/96 ns for 100Mbit/1Gbit configuration. However, all results are pointing to 75/750 Mbits. I have calculated the IPG based on the throughput that I have measured. 

In the Ethernet specification, it is mentioned that the minimum IPG is 12 bytes (96 ns), but when I try to generate high throughput traffic, I am not able to get the bandwidth/speed that was advertised.

Why is this happening, and how I can I get around this bandwidth ceiling to attain the advertised bandwidth and performance?

Solution

The PXIe-852x hardware can indeed reach 100Mbit/1Gbit speeds. However, by default PXIe-852x hardware transmits at 75% of the advertised throughput, hence the measured performance results pointing to 75/750 Mbits.

To enable maximum specified throughput of 100Mbit/1Gbit please use the Interface:Ethernet:Endpoint:Transmit Bandwidth property in your code at the configuration step and set its value to 99,999,999.