Standard parties can be up to 6 players, and Raid parties are up to twelve. Players gain experience by completing quests. Killing monsters will usually increase the size of the experience reward, but are not always central to the reward. In some cases, simply running through a dungeon from one end to the other will grant an XP reward.
DDO supports solo play, including a special "Solo" level of difficulty on many quests. But a more typical party consists of multiple characters filling roles such as "tank" (fighters, paladins, rangers or barbarians), healer (clerics), caster (wizard or sorcerer), or "support" (bard or rogue).
There are currently 5 DDO servers for the US market (merged from the original 14), named after various geographic aspects of Eberron. For the European market there were initially 5 servers, named after Eberron deities. After a server merge in early 2007, 2 remain. Characters are transferable from server to server via a request form and $25 fee. In the US, Turbine themselves deploy the game and maintain the day-to-day operations. In Europe this has been outsourced to Codemasters with the help of Alchemic Dream. In China, the game is operated by Shanda.
There are currently no servers for the Oceania market. The game distributed in Australia by Atari is the US version. Players in this region will get a ping of ~300msec to the US servers. Weekly downtimes take place during the PM hours (7pm to 12pm GMT+8) in Oceania, often on Friday nights.