  Conducting experiments in federated, distributed, and heterogeneous testbeds
is a challenging task for researchers. Researchers have to take care of the
whole experiment life cycle, ensure the reproducibility of each run, and the
comparability of the results. We present GPLMT, a flexible and lightweight
framework for managing testbeds and the experiment life cycle. \gplmt provides
an intuitive way to formalize experiments. The resulting experiment description
is portable across varying experimentation platforms. GPLMT enables researchers
to manage and control networked testbeds and resources, and conduct experiments
on large-scale, heterogeneous, and distributed testbeds. We state the
requirements and the design of GPLMT, describe the challenges of developing and
using such a tool, and present selected user studies along with their
experience of using GPLMT in varying scenarios.
