Much Different are planning to break the world record for most simultaneous users in a First Person Shooter this Sunday the 29th. The most player dense known commercial FPS is PlanetSide which supports up to 399 players in the same zone. Much Different plan to smash that with Man Vs Machine supporting up to 1000 players at the same time. All you need to play is the Unity Web Player plugin installed in the browser of your choice.
The server technology behind the game is designed to reduce lag with very large player counts. As long as you have an Internet connection capable of downloading 31 KB/s the amount of lag should depend on your distance from Stockholm, Sweden, rather than the number of players in the game. The battlefield is hosted by 8 single-threaded Unity Game Servers that each handle a section of the battlefield and they have a dynamic traffic router/load balancer, PikkoServer, that divides the battlefield between the game servers and glues the result together for the clients, many times each second. The battle itself takes place in one large zone that will contain all 1000 players at the same time.
The game will be available on their site once their countdown clock ends at 3pm GMT and is a one time only event that pits gamers against developers.
Find out more information at Much Different’s world record site, http://www.muchdifferent.com/1000PlayerFPS/