Well I don't really want to run a separate tool just to see in/out but for now I guess that could work. I was thinking about overriding the serializers functions to store the size of the bytes that are sent. Lots of games let you put up networking info to see in/out rate in kb/s.
UDP mostly over LAN. It's using normal jmonkey networking stuff like in the wiki. I've based it all on valve's networking articles as far as only sending input. I also have a separate loop to run the game physics at a fixed 60 tick rate.
Like you said its very game specific so I don't know much help you guys could give. My packets don't seem that big though? The entity game state is 3 ints, 2 vectors, 2 strings, 2 floats, and 1 boolean. Plus any relevant events which can either be 1 enum or 1 enum and 2 vectors. This is per play. I've only tested with about 3 players. This is sent at 60 fps. Is that too much?