Just thought I'd mention a few things on top of what other have mentioned in this thread. One being the difference of peer-to-peer connection and a server/client based connection. (And since I don't know for sure exactly how OFP is sending information in multiplayer, the following is mostly theory)
In peer-to-peer connections like OFP uses now, machines are passing information back and forth between each other, more information then is needed. No one machine has control over what is going on in the game world. Instead, your machine is trying to tell all the other machines in the game what is going on in your game, while their machines are trying to send the same information to you.
Another problem that I've experienced in peer-to-peer style connections is information flooding. Unless there is a way to limit the amount of data broadband users send to 56k modem users, the 56k modem will be flooded with more information then it can handle at one time.
With a server/client based connection there is one machine that dictates what is really happening in the game, and that is the server. All the other client machines will send the players movements and actions to the server. The server tells the clients what the results are. In this method the client is only sending information back and forth between his computer and the server, which is much more efficient then sending that information to everyone connected.
That is my basic (but probably somewhat close to accurate) understanding of servers, clients and connection types. Netcode refers to the way in which data is sent between the connected machines. I don't know much about that stuff, like client side prediction etc.
