The Network was a space station from which the Meson Broadcasting System (or MBS) operated in the late 22nd century.
The station was located midway between Meson Primus and Torrok. After acquiring the Black Sun Broadcasting station in 2186, MBS attached it to the outside of the Network. There was an inaccurate station guide for it, The Indispensible Network Guide, which included an out-of-date map.
The Sixth Doctor was sent to the Network by the Time Lords to stop Krllxk. He was unable to stop it from infecting the station, but managed to send it into Meson Alpha, one of the stars in the Meson system. (PROSE: Time of Your Life)