A global Internet overlay testbed is being deployed to support the distributed, shared use of resources for network research. The Global X-Bone (GX-Bone) augments the X-Bone software system, enhancing its coordination mechanisms to support deployment of local overlays to world-wide, shared infrastructure. The GX-Bone is based on the X-Bone's Virtual Internet Architecture which extends the Internet for both concurrent, parallel and recursive overlays, and provides decentralized, automated deployment and management. GX-Bone supports host virtualization through the NetFS file system, granting individual users compartmentalized access and control of host and router configuration, and the DataRouter extension to IP loose source routing that supports application control of network-layer forwarding. GX-Bone can be installed on user-modified kernels, uniquely supporting both conventional kernel-level protocol development and coordinated global infrastructure sharing.