This paper describes an experimental assessment of the Upper Atmospheric Research Collaboratory (UARC), an object-based distributed system. For the past three years, the UARC software system has enabled space scientists to collaborate on atmospheric experiments in real-time over the Internet. The UARC system provides a means for its users to view data from remote atmospheric instruments, share annotations of that data, discuss experimental results in a chat window, and simultaneously edit text manuscripts. However, UARC's distribution of atmospheric data to this geographically dispersed group of scientists is its primary mechanism for effecting their collaboration. This paper investigates the impact of UARC's implementation as a large distributed object-based software system as a means for supporting wide-area collaboratories. Specifically, it focuses on the communication performance and scalability of its object-based data distribution mechanism. First, Internet microbenchmarks are presented which characterize the UARC topology; then the results of application-level experiments are described that investigate UARC's use of NeXTSTEP's Distributed Object method invocations as a communication primitive. Finally, an analysis and discussion of the UARC system's object-based implementation concludes the paper.

Keywords: Distributed Systems, Internet, Network Performance