A method for measuring one-way link delay includes transmitting a first packet from a first network device. The first packet is passively intercepted, a first copy of the first packet is transmitted to the first network device, and a second copy of the first packet is transmitted to a second network device. A time of receipt of the first copy of the first packet is recorded as an origin timestamp at the first network device. A time of receipt of the second copy of the first packet is recorded as a receive timestamp at the second network device. A second packet including the origin timestamp is transmitted from the first network device. The second packet is passively intercepted, and a first copy of the second packet is transmitted to the second network device. The first copy of the second packet is received at the second network device, and the origin timestamp is extracted from the first copy of the second packet. Link delay from the first network device to the second network device is calculated using the origin timestamp and the receive timestamp.