To enable more precise synchronization of distributed clocks, before a high-level frame is converted to a low-level frame for transmission over a communication network, if the high-level frame includes a certain type of message, it is flagged. The flag is detected during the conversion process, and the time of detection is stored as a transmission timestamp. When a low-level frame is received from the network, it is immediately timestamped with the time of reception. The timestamped frame is then converted to a high-level frame, and if the high-level frame includes the certain type of message, the timestamp is stored as a reception timestamp.