lost network connection, etc.), the current server stops functioning and gameplay ends. A host migration feature allows one of the other players to become designated as the new host, so that the game can continue. Peer-to-Peer In the client/server model outlined elsewhere in this article, clients receive processed data from the server and display it without much thought. In the alternative "peer-to-peer" model there is no server: each "peer" instead receives the raw input streams of each other player and determines the results itself. Peer-to-peer is generally considered obsolete for action games, but it is still common in the real-time strategy genre due to its suitability for games with large numbers of tokens and small numbers of players. Instead of constantly transmitting the positions of 1000 troops, the game can make a one-off transmission of the fact that 1000 troops are selected and that the player in command of them just issued a move order. However, peer-to-peer has many disadvantages: It is very difficult to keep all peers synchronized. Minute differences between peers can escalate over time to game-breaking paradoxes. It is very difficult to support new peers joining part-way through a game. Each peer must communicate with all other peers, limiting the number of connected players. Each peer must wait for every other peer's message before simulating the next "network frame", resulting in all players experiencing the same latency as the player with the worst connection. Listen-peer Multiple listen servers collectively peer amongst themselves for listen-peer setting. This type of setting avoids the disadvantages of peer-to-peer communications among all clients and is a better alternative to dedicated servers for increased number of clients. Tickrate The rate at which a game server runs simulation steps is commonly referred to as its "tickrate". A "tick" is a number associated with each simulation step which is broadcast to clients to help them synchronise with the server. There are three reasons to limit the frequency of server simulation steps to a predefined tickrate: to conserve server and client bandwidth, to conserve server CPU time, and to allow clients to be certain of how much time has elapsed between each tick. The last point is important for internet games, as network updates from the server can arrive at different intervals or even an incorrect order. Customization Servers, particularly those of PC games, can generally be customized in ways that still allow unaltered clients to