"In the game, players use armored vehicles to fight tense battles staged in large, interactive arenas. Players could choose which side they wished to fight for, the aliens or the human defenders of Earth, and could also choose one of three different vehicles to combat with; each having its own advantages and disadvantages. Although Alien Front was fully playable for one person, it was primarily designed as an online game in which up to 8 players (up to 4 on each side) could battle it out. Players move around the arena attempting to blast each other with their weaponry, while also looking for power-ups that will enhance their ability to wreak massive destruction. Typically, the game was played for a set number of minutes, after which the team with the most kills would be declared the winners. Being killed while playing the game had no serious consequences (you simply respawned in a different part of the area you were in), but it did reflect on your win/loss score.
While the game was tremendously successful and arguably one of the Dreamcast's most critically accepted online titles, it came out so late in the lifespan of the system, that Sega's free online servers used to play the game moved to a pay model shortly after the game's release causing a tremendous shrinkage in the player base. Soon after, the Dreamcast's online servers went down for good (when Sega officially stopped supporting the console) and Alien Front was returned to being a single-player experience. While the game was certainly not revolutionary, it does have a place in gaming history as the first console title with online play to allow its players to communicate with their real voices using a supplied microphone attachment. While a player could only send a very short few seconds of his voice into the game, it made the competition much more tangible when vocal taunts and commands could be heard during the gameplay."
Source: Wikipedia, "Alien_Front_Online," available under the CC-BY-SA License.