Formation of suitable overlay-network topologies that are able to reflect the structure of the underlying network-infrastructure, has rarely been addressed by peer-to-peer applications so far. Often, peer-to-peer protocols restrain to purely random formation of their overlay-network. This leads to a far from optimal performance of such peer-to-peer networks and ruthlessly wastes network resources. In this paper, we describe a simple mechanism that uses programmable network technologies to improve the topology formation process of unstructured peer-to- peer networks. Being a network service, our mechanism does not require any modification of existing applications or computing systems. By that, it assists network operators with improving the performance of their network and relieves programmers from the burden of designing and implementing topology-aware peer-to-peer protocols. Although we use the well-know Gnutella protocol to describe the mechanism of our proposed service, it applies to all kinds of unstructured global peer-to-peer computing applications.