How gigabit ethernet can replace firewire for system migration

As long as you have two fairly modern machines, you can connect them without a router ..

Creating a small Ethernet network

...Some later Macintosh computers can automatically detect and reconfigure pinouts so that a crossover cable is not required and/or may be used interchangeably with a standard cable.

I'd forgotten about cross-over cables, I wonder what year Macs became auto-configuring.

Incidentally, in my experience Gigabit ethernet connected drive services feel much faster than locally connected USB drives.