At home I have both an iMac and a Mac Mini, both running OS X 10.6.6. Both connect to the internet via the same 802.11n wireless network, however performance can be very poor when I perform a large file transfer between the two - largely, I suspect, due to the fact that they are competing for the same slice of spectrum when the sender is going to the router and the receiver is coming back from the router.
It occurs to me, however, that they are both sitting on the desk next to each other. Is it possible to string an Ethernet cable between them, so they can talk directly, but they will use the Ethernet link only to talk to each other - any messages for the internet at large or the rest of the LAN go straight onto AirPort?
Ideally this should be as transparent as possible, so that I can refer to them by the same (Bonjour) host name from either Mac, or another device on the LAN. In addition, it must work when either machine is switched off - I don't want to route the internet connection of one through the other, and neither can be guaranteed to be on.