4 Taming Live Coordinate Systems


4 Taming Live Coordinate Systems

From our experience tuning a network coordinate system on PlanetLab, we developed two techniques that lead to more stable and accurate coordinates on a small ``live'' system [18]. The Azureus and Harvard teams worked together to integrate these techniques into the Azureus code. After confirming that these techniques worked as expected, we found and resolved a new problem: skewed neighbor sets. This problem particularly disrupts large-scale, live coordinate systems like Azureus that rely solely on other application communication for maintenance (i.e.they have zero maintenance costs) and has has been suggested as a goal for coordinate systems [9]. Through experimentation with these techniques in simulation and periodic measurement of the live system, we arrived at coordinates that are not perfect, but are a satisfactory start. We include a review of the techniques we developed as part of our previous research in Section 4.1 and describe our new technique, neighbor decay, in Section 4.2.

Subsections

Jonathan Ledlie 2007-02-23