Abstract
We uncover the reality of traffic differentiation in mobile virtual network operator (MVNO) networks and shed new light on its negative impact on the accuracy of available bandwidth (i.e., the unused capacity of an end-to-end path) estimation methods that use a probing packet train (i.e., a set of multiple probing packets). To the best of our knowledge, we report, for the first time, that multiple operational LTE MVNO networks in the Asian region are very likely to differentiate traffic according to the time of day. We find, also for the first time, that when a sender transmits a packet train to a receiver during a period of traffic differentiation, the packet loss rate of the packet train jumps up, thus degrading the accuracy of available bandwidth estimation as the packet train is corrupted by the high packet loss rate. As a countermeasure, we propose a method called PathQuick4 for accurately estimating the available bandwidth while remaining robust against traffic differentiation. The key idea is that we dynamically judge whether traffic differentiation occurs through inline measurement of packet loss characteristics by using a single packet train itself, without transmitting any extra probing packets. From this judgement, we then choose either packet-train-or packet-pair-based bandwidth estimation as appropriate. An experimental evaluation over three operational Japanese LTE MVNO networks showed that the overall estimation error of PathQuick4 across the three MVNOs during periods of traffic differentiation was close to an order of magnitude less than the error of a conventional method.