I have a 2014 MBP running 10.13.6.
The first two pics show my baseline ethernet performance, with the Speedtest desktop app, and with Fast.com, respectively. I get this same performance with wireless, ethernet→thunderbolt (Apple Thunderbolt Ethernet Adapter), and ethernet→USB (Monoprice [Realtek 1853] USB Ethernet Adapter, advertised as USB 3.0, 10/100/1000BASE-T).
The next pair show what I get with ethernet→USB with the Apple USB Ethernet Adapter (advertised as USB 2.0, 10/100BASE-T).
Both the Monoprice and Apple USB Ethernet adapters were plugged directly into the USB 3.0 port on my Mac.
Summary, and other info.:
My question: It seems that the Apple USB Ethernet adapter should have a ceiling of either 100 Mbps (100BASE-TX) or 480 Mbps. But I'm only getting low-30's Mbps download speeds with the Apple device. What should be its actual peformance?
BASELINE PERFORMANCE WITH MONOPRICE (REALTEK 1853) USB ETHERNET ADAPTER PLUGGED INTO USB 3.0; GET SAME PERFORMANCE WITH BOTH APPLE THUNDERBOLT ETHERNET ADAPTER, AND WIRELESS
PERFORMANCE WITH APPLE USB ETHERNET ADAPTER PLUGGED INTO USB 3.0