Abstract. The paper introduces a new receiver-based active end-toend measurement technique, called the Single-Double Unicast Probing (SDUP), to estimate the rate of losses which occur on the shared network path of two flows. A comprehensive performance evaluation and a comparison between the SDUP and an existing technique having the same objective, the Striped Unicast Probing (SUP) [6], is carried out. We show that our proposed SDUP method has smaller bias (i.e., 20% smaller absolute error) and smaller variance compared to that of SUP. Besides the slightly higher accuracy, an important advantage of our method is that only one measurement equipment is needed at only one receiver, instead of deploying units to both receivers. Furthermore, with one sender and receiver pair we can measure not only one shared path, but any partial path that begins at the sender and locates on the path from the sender to the receiver. Our method is less intrusive and causes less bursty traffic compared to t...