My thesis has been to design and implement a directory service that will enable us to do just that. The bulk of proposed pervasive computing devices such as PDAs and cellular telephones operate as thin clients within a larger infrastructure. To access services within their local environment, these devices participate in a service discovery protocol which involves a central directory which registers all services in the local environment. These central directories are typically isolated from each other and devices that move across service discovery domains have no access to information outside their current local domain. We then propose an application level protocol called VIA that enables data sharing among discovery domains.
Directories maintain a table of active links to other directories that share related information.
A set of linked directories forms a data cluster that can be queried by devices for information. The data cluster is distributed, self-organizing, responsive to data mobility, and robust to failures. Using application-defined data schemas, clusters can organize themselves into a hierarchy for efficient querying and network resource usage. Through analysis and simulation we analyze the behavior of VIA under different workloads and show that the protocol overhead for both maintaining a cluster and handling failures grows slowly with the size of the cluster. Ad-hoc routing in wireless networks.