From Halopedia, the Halo wiki
Gateway was a vessel of unknown class used by the United Rebel Front in the Eridanus system. In 2513, the ship participated in the battle against the UNSC fleet over Eridanus II. When the rebels began to retreat, Gateway was having problems with its Shaw-Fujikawa Translight Engine. The frigate Iliad, under the command of Colonel Robert Watts, bought Gateway some time until they could get their slipspace drive back operational and successfully escape into a designated renzedvous point.