In a software defined network having switches including first and last switches and intermediate switches, wherein a default routing path exists between the first and last switches, a system and method are provided for computing path latency. The method includes inserting a respective monitoring rule(s) in each switch, mandating for each switch, forwarding a received rule matching packet to a next switch, and further mandating for the first switch and the last switch, sending a PacketIn message to a controller. The method includes inserting, in each switch, a respective monitoring probe(s) matching the respective monitoring rule(s) in a same switch to initiate mandates specified by the respective monitoring rule(s) in the same switch responsive to an arrival of the packet thereat. The method includes time-stamping the PacketIn messages to generate PacketIn timestamps, aggregating the PacketIn timestamps, and estimating the path latency from an aggregation of PacketIn timestamps.