TopHat is a measurement service for PlanetLab, the flagship testbed of the
OneLab2 project, and is designed by UPMC who is in charge of the Topology
Information workpackage within the project. It offers a dedicated service that
provides network topology information to PlanetLab users and applications
running on PlanetLab.

TopHat's niche lies in its support of the entire lifecycle of an experiment:
assisting users during experiment setup in choosing the nodes on which the
experiment will be deployed; at run time, it providing live information to
support adaptive applications and experiment control; and supporting
retrospective analysis through access to archived data. 

TopHat supplies measurements to its users thanks to its own TDMI platform, which
are supplemented by drawing upon several independent specialized measurement
infrastructures: DIMES, ETOMIC, SONoMA, and the Team Cymru service, some of
which have a proven track record of excellence in providing specialized
measurements to the research community.

Website: http://www.top-hat.info