Comment 3 for bug 46081

There's perhaps a similar bug report about samba. In both cases I believe the slowdown happens because of the way samba interacts with ethernet drivers. https://bugs.launchpad.net/ubuntu/+source/samba/+bug/84782

analogue - realtek, linksys and trendnet perhaps using realtek chipset/driver, which seems to be affected the most. Also I think some Marvell-Yukon adapters are affected (at least the one you find built into NF4 motherboards).