Given out-of-band information, a subscriber can retrieve tracks from a publisher (including a relay) without any previous MOQT messages besides SETUP. However, MOQT provides in-band messages for a publisher to advertise the namespaces it has tracks in, and for a subscriber to discover the namespaces a publisher knows.
Discovery of MOQT servers is always done out-of-band: MOQT does not specify how an endpoint learns where to establish a session. The discovery described in this section takes place within an established session.