A method for testing a communication network includes transmitting a flow of test packets over a path through the network. The flow includes a series of bursts of the test packets separated by intervals having an interval duration, each burst comprising a sequence of the test packets and having a burst duration less than the interval duration. Arrival characteristics of the test packets in the flow are measured at a receiving end of the path. The arrival characteristics include at least one of a packet loss characteristic, a packet delay characteristic, and a packet jitter characteristic. A quality defect in the network is detected based on the measured arrival characteristics.