It's a left over from Tribes 2 where the server kept a tab delimited list of unique identifiers, one per player, that was apart of a master server authentication token system. Basically how it did work was that the player would log into Tribes 2 for online gaming and the master server would pass a GUID (global unique identifier) to the player's game client as a token to signify that the login details were accepted. The game client then passed that token over to the game server of which the player chose to join to so that the game server could then take that token and ask the master server if that GUID was valid, and if so the player is then allowed to continue on joining the game, else the player is dropped for having an invalid token.
Torque Owner Nathan Martin
TRON 2001 Network