A Facility for Experimenting Distributed Software in the Internet

To test distributed software in the Internet we need many experimental sites in diierent physical locations. To ease the experimental setup, we have developed a facility for a study of distributed transaction processing in the Internet. The facility emulates remote sites by local machines, and emulates a true Internet communication environment in a local area network, by routing the inter-site communication through actual Internet hosts. This provides a mechanism to conduct experiments without any designated experimental sites except for the local ones, yet the results are as genuine as in the real experiments. It also supports a trace-driven emulation method that measures the inter-site communication of the Internet and uses the measurement data to generate empirical values for delay and message loss between two local sites. We have studied these approaches and observed that they are feasible and reliable. We have realized these two approaches in a communication package called the WANCE tool, which can be used to test distributed software, without changing the application programs. We have evaluated the emulation approach by comparing it with real experiments. The results are statistically acceptable. and AT&T. y This paper is an extension of a workshop presentation 1].