Players can navigate through the lobby server space simply by deleting themselves from their current group and adding themselves to a new group. At any time, the IDirectPlay3::EnumGroupsInGroup method can be called to determine what groups are linked to the current group.
In general, the scope of the lobby session visible to a player is limited by the groups the player is part of. This is done to limit the amount of information that the server must download to the client.