Network fragmentation occurs when the accessibility of a network-based resource to an observer is a function of how the observer is connected to the network. In the context of the Internet, network fragmentation is well-known and occurs in many situations, including an increasing preponderance of network address translation, firewalls, and virtual private networks. Recently, however, new threats to Internet consistency have received media attention. Alternative namespaces have emerged as the result of formal objections to the process by which Internet names and addresses are provisioned. In addition, various governments and service providers around the world have deployed network technology that (accidentally or intentionally) restricts access to certain Internet content. Combined with the aforementioned sources of fragmentation, these new concerns provide ample motivation for a network that allows users the ability to specify not only the network location of Internet resources they want to view but also the perspectives from which they want to view them. Our vision of a Perspective Access Network is a peer-to-peer overlay network that incorporates routing and directory services that allow non-hierarchical organization. In this paper, we present the design, implementation, and evaluation of a directory service for such networks. We demonstrate its feasibility and efficacy using measurements from a test deployment using PlanetLab.Engineering and Applied Science
