Dynamic Server Selection using Bandwidth Probing in Wide-Area Networks
Carter, Robert L.
Crovella, Mark E.
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Citation (published version)Carter, Robert; Crovella, Mark. "Dynamic Server Selection using Bandwidth Probing in Wide-Area Networks", Technical Report BUCS-1996-007, Computer Science Department, Boston University, March 18, 1996. [Available from: http://hdl.handle.net/2144/1584]
Replication is a commonly proposed solution to problems of scale associated with distributed services. However, when a service is replicated, each client must be assigned a server. Prior work has generally assumed that assignment to be static. In contrast, we propose dynamic server selection, and show that it enables application-level congestion avoidance. To make dynamic server selection practical, we demonstrate the use of three tools. In addition to direct measurements of round-trip latency, we introduce and validate two new tools: bprobe, which estimates the maximum possible bandwidth along a given path; and cprobe, which estimates the current congestion along a path. Using these tools we demonstrate dynamic server selection and compare it to previous static approaches. We show that dynamic server selection consistently outperforms static policies by as much as 50%. Furthermore, we demonstrate the importance of each of our tools in performing dynamic server selection.