In a method for exchanging packets between first and second nodes of a packet-switched network, each packet comprises two fields settable to an idle value or measurement value. The first node transmits to the second node first packets having a filed set to measurement value. Upon reception of each first packet, the second node transmits back to the first node a second packet having a field set to measurement value. Upon reception of each second packet, the first node transmits to the second node a third packet having another field set to measurement value. A packet loss measurement is calculated as a difference between the number of first packets and the number of third packets.