Large-scale distributed applications need latency information to
make network-aware routing decisions. Collecting these measurements,
however, can impose a high burden. Network coordinates are a scalable
and efficient way to supply nodes with up-to-date latency estimates.
We present our experience of maintaining network coordinates on
PlanetLab. We present two different APIs for accessing coordinates:
a per-application library, which takes advantage of application-level
traffic, and a stand-alone service, which is shared across applications.
Our results show that statistical filtering of latency samples
improves accuracy and stability and that a small number of neighbors
is sufficient when updating coordinates.