Last updated on December 26, 2018
Solution: provide customers with managed gigabit switches and train them to configure the switches manually. Not an ideal solution. I discovered today another workaround… the cause is 802.3x flow-control. Disabling flow-control fixes the problem:
Problem: any sleeping computer on a gigabit network causes all multicast traffic to drop to 10Mbps.
However this means that every device on every customers network would need to turn off auto negotiation, then manually turn flow-control off. Turning off auto-negotiation is a very bad idea. Not a workable solution. One example: I notice that on my dumb, old gigabit switch,
sudo ifconfig en0 -mediaopt flow-control
- sleeping machine has flow control ON , link light ON, 1000Mbps light is off
- sleeping machine has flow control OFF, link light ON, 1000Mbps light is lit.