Client

The client will do all things remotely from server. which means: the client gets all player statusses from server and it functions the same as at were an single player game.

Server

The server will run continuesly realtime: the server will have a map that will run at the local server time, so the local server time is equal to ingame time.
The server will check practically everything, so that the network load can be minimal. This way, lots of people can be on one server. unfortunatly the CPU load will be quite heavy.

Server & Client interaction

the server sends a burst of either all player statusses to all players or sends a burst of all visible player statusses to each player.
the client sends his own actions to the server. this way the network load is quite minimal.

don't know yet if maps, models, skins,... loading can be included in the same server, maybe it's better to make one general server that contains all that.

important note: to save network loads and usage, we have to make all gaming connections datagram packets, and I think we can actually limit the bytes of that package to less then 32 bytes (including overhead) for a client to server status update.

Server & Server interaction

there is an idea to get even more players on the same game and that is using more of these servers, for example: suppose we have such a server in europe and in US. the europe server runs a 'europe' map and the US server a 'US' map, because of time differences, we were thinking of supplying sea between those servers and given enough of those servers, one could possibly have an entire globe... Needless to say that the maps could be extremely big.
note: these maps don't have to be real-life maps.

there is a second idea:
having a lot of subservers hosting portions of the map of one of those big servers. a client could in fact then be connected to multiple of these servers and receive statusses from them. don't exactly know if that stabilizes the network load though.

Client & Client interaction

chatting should be done client to client and what you type and/or say will be sent to all players in your direct area, maybe even depending on how loud you type and/or speak;-). long distance can be accomplished by using walkie talkies and selecting a frequency.