Passive monitoring and measurement of network round trip time delay

A method is described and in one embodiment includes receiving at a first network element of a communications network a first packet corresponding to a first traffic flow from a first end user device to a second end user device at a time T1; receiving at the first network element a second packet corresponding to a second traffic flow from the second end user device to the first end user device at a time T2; calculating by the first network element a difference α1 between the time T1 and the time T2; creating at the first network element a first record including the calculated difference Δ1; and providing the first record to a network collector device, wherein the network collector device compares the first record with a second record received from a second network element to determine a Round Trip Time ("RTT") delay for the communications network.