A subspace relay network was collection of interlinked subspace relays allowing for communications across vast interstellar distances.
A network of subspace relay stations had been established throughout the Sol system, permitting real-time communications (or at least with acceptable delays) by 2100. (The Starfleet Museum)
The Federation maintained a subspace relay network to facilitate interstellar communications. (TNG: "Aquiel")
The Hirogen controlled a vast network that spread from the Delta Quadrant to the Alpha Quadrant. (VOY: "Message in a Bottle")