Data Transfer Rates RNDIS vs Belcarra USBLAN for Windows

Measured in MegaBytes per second (MB/s) the graph illustrates gadget CDC-ECM protocol data transfer speed vs. Microsoft's RNDIS protocol using three simple web-related network tests all done with Linux-line tools, on an Overo Gumstix, or on the PC using the Cygwin tools to give a Linux-like environment (see www.cygwin.com).

• wget (OUT) -- using wget on the device to retrieve a large file.  The traffic measured is in the OUT direction. Output (file retrieved) is discarded.
• wget (IN) -- using wget on the PC to retrieve a large file. Output is discarded
• wget OUT- bidirectional
• wget IN - bidirectional
• combination of the previous 2

The weakness of g_rndis is that the bidirectional speeds are 1.4 MB/s and 3.44 MB/s. The aggregate speed 4.8MB/s is perhaps not dreadful, but 1.4MB/s in the bidirectional (2 way) OUT direction is well below the CDC-ECM protocol/implementation giving up significant performance and perhaps compromising the usefulness of a device. The combined throughput performance of the gadget ECM with USBLAN was 11.44 MB/s compared to only 4.82 MB/s using RNDIS.