Quick and simultaneous estimation of available bandwidth and effective UDP throughput for real-time communication

We propose a method, called PathQuick2, for quickly and simultaneously estimating both of the available bandwidth that is unused capacity of an end-to-end path and the effective UDP throughput that is the receiving rate of an UDP flow which can pass through the path, with a single measurement. In PathQuick2, a sender transmits a probing packet train (i.e., a set of multiple probing packets) that each packet is placed at an equal time interval, and each packet size increases as the packet sequence proceeds. A receiver produces the estimated available bandwidth and the estimated effective UDP throughput at the same time from the single packet train. To this end, the receiver detects a packet at which the observed time intervals begin increasing, and the per-packet receiving rate becomes the estimated available bandwidth. Then, the receiver detects a packet at which the observed per-packet receiving rates stop increasing even if the packet sequence proceeds, and the per-packet receiving rate becomes the estimated effective UDP throughput. Our evaluation of PathQuick2 has shown that its estimation duration is only 182 ms, and its probing load is about 90 kB which is more than 160 times as light as a direct measurement of effective UDP throughput. PathQuick2 can provide two useful metrics for real-time communication applications such as video chat and video conferencing; the available bandwidth indicates an upper limit of video sending rate which enables stable video communication without packet loss, and the effective UDP throughput indicates an upper limit of video receiving rate that can pass through an end-to-end path, with a given video sending rate.