Hourglass: An Infrastructure for Connecting Sensor Networks and Applications

Abstract

The emergence of computationally-enabled sensors and the applications that use sensor data introduces the need for a software infrastructure designed specifically to enable the rapid development and deployment of applications that draw upon data from multiple, heterogeneous sensor networks. We present the Hourglass infrastructure, which addresses this need. Hourglass is an Internet-based infrastructure for connecting a wide range of sensors, services, and applications in a robust fashion. In Hourglass, a stream of data elements is routed to one or more applications. These data elements are generated from sensors inside of sensor networks whose internals can be entirely hidden from participants in the Hourglass system. The Hourglass infrastructure consists of an overlay network of well-connected dedicated machines that provides service registration, discovery, and routing of data streams from sensors to client applications. In addition, Hourglass supports a set of in-network services such as filtering, aggregation, compression, and buffering stream data between source and destination. Hourglass also allows third party services to be deployed and used in the network. In this paper, we present the Hourglass architecture and describe our test-bed and implementation. We demonstrate how our design maintains streaming data flows in the face of disconnection, allows discovery of and access to data from sensors, supports participants of widely varying capabilities (servers to PDAs), takes advantage of wellprovisioned, well-connected machines, and provides separate efficient communication paths for short-lived control messages and long-lived stream-oriented data. 1