|Informative Information for the Uninformed
Battle.net was originally setup as a small number of linked servers placed at various strategic geographical locations. They were ``linked'' in the sense that players on one server could interact with players on a different server as seamlessly as with players connected to the same server. This architecture eventually proved unsupportable, as increasing usage of Battle.net led to the common occurrence of "server splits", in which one or more servers would be unable to keep up with the rest of the network and become temporarily disconnected.
Eventually, the system was split into two separate networks (each starting with a copy of all account and player data present at the time of the division): The Asian network, and United States and European network. Each network was comprised of a number of different servers that players could connect to in an optimized fashion based on server response time.
Some time later, even this system proved untenable. The network was once again permanently fragmented, this time splitting the United States and European network into three subnetworks. This is the topology retained today, with the networks designated ``USEast'', ``USWest'', ``Europe'', ``Asia''. It is believed that all servers in a server network (also referred to as a ``cluster'' or ``gateway'') are, at present, located at the same physical hosting facility on a high-speed LAN.
As new game requirements came about, a new architecture for Diablo II and Warcraft III as required. In these cases, games are hosted on Blizzard-operated servers and not on client machines in order to make them more resilient from attempts to hack the game to gain an unfair advantage. There are significant differences to how this is implemented for Diablo II and Warcraft III, and it is not used for certain types of games in Warcraft III . This resulted in a significant change to the way the service performs it's primary function, that is, game matchmaking.