Challenges and Lessons Learned in Measuring Path RTT for Proximity-based Applications

Path RTT plays a crucial role in several overlay network construction protocols, peer-to-peer applications, and proximity-based server redirection in such applications as multiplayer gaming and content distribution network. The RTT of a path is usually estimated as the minimum of a number of measurements. The number of probes reported used by these applications ranges from a few probes to more than 200. Given the potential for wide deployment of these services and applications, the bandwidth consumed in measuring path RTT becomes significant. We look at the challenges in capturing the minimum RTT along a path, using minimum bandwidth while maintaining measured RTT close to minimum path RTT. Our analysis builds on the RTT phase-plot used by Bolot [1]. We illustrate the use of our measurement techniques with a set of Internet experiments.