A pluggable transceiver module (200) comprising a line receiver (208) connected to a unit interface transmitter (202), a line transmitter (206) connected to a unit interface receiver (204) and a timestamp counter (210) adapted to generate counter values based on clock signals received from an external source and to send the counter values to the line transmitter (206) and to the line receiver (208). The line transmitter (206) and the line receiver (208) are adapted to associate timing packets in a stream of data packets transmitted and received by the pluggable transceiver module (200) with counter values output by the timestamp counter (210).