That is, UDP and TCP aren't good for realtime work. I will not summarise the points made by the people of this camp especially since this is comp.unix.wizards. I'm still posting this summary anyway since I think it is interesting. The problem you are describing is that faced by the Financial Services industry in distributing data. Typically the data is something like foreign exchange rates or news or something like that.
Ethernet makes no realtime guarantees.
One thing I have found though, is that if you are want realtime images, then the load of the machine on which you are processing the images may well be more important than the bandwidth of the network. Then so long as the throughput is high enough you can pump it through whatever you want and resynchronize it later. Ethernet's weakness is a couple of orders of magnitude below the pain threshhold for human- initiated transactions. Other network topologies have their own problems. Ignored the problem.