The FastTrack overlay: A measurement study

Both in terms of number of participating users and in traffic volume, FastTrack is one of the most important applications in the Internet today. Nevertheless, because FastTrack is proprietary and uses encryption, little is understood about FastTrack's overlay structure and dynamics, its messaging protocol, and its index management. We have built two measurement apparatus-the FastTrack Sniffing Platform and the FastTrack Probing Tool-to unravel many of the mysteries behind FastTrack. We deploy the apparatus to study FastTrack's overlay structure and dynamics, its neighbor selection, its use of dynamic port numbers to circumvent firewalls, and its index management. Although this study does not fully solve the FastTrack puzzle, it nevertheless leads to a coherent description of FastTrack and its overlay. Furthermore, we leverage the measurement results to set forth a number of key principles for the design of a successful unstructured P2P overlay. The measurement results and resulting design principles in this paper should be useful for future architects of P2P overlay networks as well as for engineers managing ISPs.