Large-scale experimentation in varying types of environments is difficult to achieve, and until recently, experimenters have had to either construct their own platforms or rely on simulation, emulation, or analysis to gain results. However, these methods largely do not provide adequate or verified results. There lacked a viable model for the federation of large-scale testbeds that reconciled the challenges posed by how to provide a single entry point to access heterogeneous and distributed resources, and how to federate these resources that are under the control of multiple authorities. Efforts such as the FIRE initiative in Europe and GENI in the United States have worked to develop such a model, and the OneLab experimental facility, which came online in 2014, realizes this model, making a set of world-class testbeds freely available to researchers through a unique credential for each user and a common set of tools. OneLab provides a large-scale facility for rapid and remote testing that produces exhaustive results, at no charge to the experimenter. We allow users to deploy innovative experiments across our federated platforms that include the embedded object testbeds of FIT IoT-Lab, the cognitive radio testbed of FIT CorteXlab, the wireless testbeds of NITOS-Lab, and the internet overlay testbeds of PlanetLab Europe (PLE), which together provide thousands of nodes for experimentation. The OneLab portal allows single-entry point access to these platforms, and provides users with unique credentials. This is made possible through the adoption of Slice-based Federation Architecture (SFA), an API for authentication and authorization that was conceptualized by the GENI initiative in the US, where each authority authenticates users and authorizes access to the resources; and MySlice, the portal technology that we have developed to federate heterogeneous resources.