PlanetLab is a global platform for evaluating and deploying network services. It currently includes nearly 700 nodes, spanning over 335 sites and 35 countries, and hosts over 500 experimental services. In this Distinguished Lecturer Series, Larry Peterson, Princeton University, identifies the requirements PlanetLab addresses, presents the design principles that follow from them, and outlines the resulting PlanetLab architecture. He also briefly discusses some of the lessons learned about building large network systems. From the Series:CSE Colloquia - 2007