Time synchronization for network devices with reduced processing requirements for slaves. A master sends a time request message to the slave, including the time T1 at which it sent the message. The slave receives the time request message and records the time T2 at which it received the message. The slave sends a time response message to the master that includes the time T2, the time T1 at which the time request message was sent, and the time T3 at which it sent the time response message. The master receives the time response message and records the time T4 at which it was received. The master estimates the one-way delay from the times T1, T2, T3 and T4. The master determines whether the slave's clock is synchronized with the master's clock and if not, sends a sync message that contains information usable by the slave to sync its clock.