Is there any upper limit to the size of a frame? Because I'm not sure if I have enough ram in my 328P to store a entire frame in RAM?

I'm going to have to do some research on interrupts. This is exactly the kind of project I need to teach myself low-level AVR things, and on the surface it seems easy, but I just need to go ahead and set something up.

Now, another question --- suppose that I wanted to make this go in-line between two phonenet nodes --- the data will be the same, but half duplex, correct?

I'm going to find a S-video cable and destroy it, and go ahead and hook this up to a arduino and start playing with it.