NASA's overall communications network. It uses voice and data communications to connect the central communications terminal (CCT) of the Network Operations Control Center (NOCC) at the Jet Propulsion Laboratory with other facilities, including the three deep-space communications complexes (DSCCs).

The communications links are by satellites, land lines, submarine cables, and terrestrial microwave. The GCF circuits carry information critical to space missions, such as command, tracking, and monitor and control data. They also carry telemetry from shuttle, satellite, and lunar missions, and data concerning radio and radar astronomy observations.