NCR (Network Clock Reference) is a procedure to provide the master clock (i.e. time information) of the satellite to all its user terminals. Typically, NCR packets are provided periodically over a continuous DVB-S2 or DVB-S2X link. The receiving user terminal uses the knowledge of the master clock in the system to determine when it is allowed to transmit data in a time-division multiple access (TDMA) system, such as DVB-RCS or DVB-RCS2.