Where is my peer ? Evaluation of the Vivaldi network coordinate system in Azureus

Network coordinates allow to estimate the latency among a large number of hosts in a scalable way. Recently, Azureus, a popular implementation of BitTorrent, has implemented network coordinates.We have developed a crawler that allows us to obtain from the network coordinates over one hundred thousand peers running Azureus and to measure the network and application level round trip times to these peers. Our measurements confirm that network coordinates allow to correctly estimate the round trip time between two peers. Our measurements also show that the round trip times from our crawling host to a set of peers located in the same country can vary between a few tens of milliseconds to more than one second. This high variance is due to the large buffers in the ADSL access links, which can increase the round trip time by hundreds of milliseconds. As a consequence, network coordinates and round trip estimations in general cannot be used to select peers that are "nearby", such as peers connected to the same ISP or located in the same country.