3. Jumbo Frame Test

Before running routing tests, I first wanted to check out the Jumbo Frames feature to see if it really could boost gigabit Ethernet throughput. I connected two systems running WinXP SP2 - one an Athlon 64 3000+ w/ 512 MB, the other a 2.4 GHz Pentium 4 w/ 504 MB.

Each machine had an Intel Pro 1000/MT desktop adapter with 8.5.14.0 (3/8/2005) driver. The adapters were both set to "Auto Detect" mode and reported connecting at 1000Mbps Full Duplex.

The adapters allow setting jumbo frame sizes of 4088, 9014 and 16128 Bytes. But since the RX3141's switch supports only up to 9K frame sizes, I limited my testing to the 4088 and 9014 settings.

Figure 7: Gigabit Ethernet throughput comparison
(click on the image for a larger view)

Figure 7 shows that average throughput got a little over a 30% boost when a 4088 Byte frame size was used (the top trace in the plot). But boosting frame size up to 9014 Bytes was counter productive, resulting in lower average throughput, but more importantly, higher throughput variation. This fallback in throughput at higher frame size is not due to anything in the 3141, but due instead to hardware and software limitations in the two computers used for the test.