Are virtualized overlay networks too much of a good thing?

The majority of recent high-profile work in peer-to-peer networks has approached the problem of location by abstracting over object lookup services. Namespace virtualization in the overlay layer provides load balance and provable bounds on latency at low costs.We contend that namespace virtualization comes at a significant cost for applications that naturally describe their data sets in a hierarchical manner. Opportunities for enhancing browsing, prefetching and efficient attribute-based searches are lost. A hierarchy exposes relationships between items near to each other in the topology; virtualization of the namespace discards this information even if present at client, higherlevel protocols.
We advocate encoding application hierarchies directly into the structure of the overlay network, and revisit this argument through a newly proposed distributed directory service.