A slave node (300) is slave equipment that operates in accordance with a control frame transmitted from a master node (200). The slave node calculates a control frame statistic that is a statistic of one or more control frames transmitted from the master equipment and estimates a master environment value based on the calculated control frame statistic. The slave node measures a slave environment value. The slave node estimates a frequency deviation of a master clock based on the estimated master environment value and estimates a frequency deviation of a slave clock based on the measured slave environment value. The slave node modifies a clock value of the slave clock based on a difference between the frequency deviation of the master clock and the frequency deviation of the slave clock.