Accurate Time-Stamping of Outbound Packets

A network device includes a port, a transmission pipeline and a time-stamping circuit. The port is configured for connecting to a network. The transmission pipeline includes multiple pipeline stages and is configured to process packets and to send the packets to the network via the port. The time-stamping circuit is configured to temporarily suspend at least some processing of at least a given packet in the transmission pipeline, to verify whether a pipeline stage having a variable processing delay, located downstream from the time-stamping circuit, meets an emptiness condition, and, only when the pipeline stage meets the emptiness condition, to time-stamp the given packet and resume the processing of the given packet.