Courier is a group communication tool, based on the publish/subscribe principle, i.e., applications can register their interest in receiving certain types of events as subscribers and they can publish events to other subscribers. Communication is asynchronous and anonymous. Courier is implemented in C and currently available for the Unix environment only. It can be used for a variety of settings (sensor networks, wireless/mobile systems, Internet-scale distributed systems, clusters, etc.), however our current focus is on wireless systems such as sensor networks. Here, the focus of our current work is on multi-constraint event communication and network management, including adaptive routing protocols in multi-hop networks, etc.

A monthly snapshot of the source code (and some documentation on how to use it) is provided on our lab's wiki. Current projects performed as part of the Courier effort include:

RTMC: Real-Time MultiCast (RTMC) is a protocol that energy-efficiently disseminates data in an ad-hoc or sensor network to several destinations (sinks), while meeting each sink's unique real-time requirements. Further, RTMC also considers energy efficiency in multicast tree establishment. RTMC has been implemented as extension to the Jist/SWANS simulator.
• SA-DSR: Stability Aware Dynamic Source Routing is our contribution to disruption-tolerant networking. SA-DSR considers multiple reliability aspects, e.g., it predicts the "awake time" of a multi-hop route to prevent interruptions in communication caused by wireless network cards entering low-power sleep modes. SA-DSR has been implemented in the Jist/SWANS simulator and an implemention in Courier is underway.
• DETOUR: This project exploits the presense of multiple routes between the same source and sink to improve end-to-end QoS (e.g., latency management and energy efficiency).
• Clock Synchronization: In mobile environments, traditional (e.g., client-server based) clock synchronization approaches are too rigid and slow. This work addresses the design of an opportunistic clock synchronization approach that operates efficiently and rapidly in mobile environments, where individual nodes can tune the synchronization to meet their needs for clock accuracy.
• Efficient Code/File Distribution: In large wireless environments (e.g., sensor networks), it is often necessary to distribute files to all (or many) nodes, e.g., to install new software releases. This protocol efficiently distributes files across such networks (and installs/starts) them if these files are executables.
• Asymmetric Geographic Forwarding: Most routing protocols assume symmetric links between two nodes, but many networks have numerous asymmetric links (e.g., heterogeneous radio devices). AGF modifies the GF protocol such that asymmetric links can also be exploited, thereby potentially improving the QoS of multi-hop communications.