Network testbeds for developing, deploying, and experimenting with new network services have evolved as recent rapid progress in virtualization technology. This paper proposes a new network testbed that enhances PlanetLab and is based on a hosted virtual machine monitor (VMM) as a virtual execution environment (VEE) for network services to run on. This paper reports our experiences in developing such a prototype network testbed employing Kernel-based Virtual Machine (KVM) as a hosted VMM. The paper examines the performance and scalability of the prototype to see whether or not it fulfills what we believe to be the requirements for a new network testbed. Categories and Subject Descriptors C.2.1 [Computer-Communication Networks]: Network Architecture and Design General Terms Design, Implementation, Performance Keywords Network testbed, Virtualization, Virtual machine, Hosted Virtual machine monitor