P2P and Grid computing are two paradigms that are increasingly used in today's computing environments; their potential to provide better quality of service to users is very promising compared to the cost involved. This paper presents a hierarchical virtual network topology built on top of a physical one, which is used to manage distributed resources in a Grid environment. The virtual topology defines an efficient and robust virtual machine, which will serve as a distributed computing platform. This topology is called THON (Tessellation-based Hierarchical Overlay Network) and is the successor of the Treep topology. THON is exploited in DGET, a data-grid middleware environment, and provides P2P resource discovery and load balancing. Here, we present the virtual topology theoretically and we show that this topology is very scalable, robust, loadbalanced, and easy to construct and maintain. The topology efficiently exploits the heterogeneity of the network while limiting the overhead introduced by the overlay maintenance.