EMPOWER: A Cluster Architecture Supporting Network Emulation
IEEE Transactions on Parallel and Distributed Systems
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Network emulation systems are widely used to explorethe behavior of network protocols and to test and evaluateprotocol implementations and applications. The majorproblem of network emulation systems is its scalability interms of emulation capacity and emulation capability ofspecific network parameters such as maximum emulatedbandwidth and emulated packet delay of the system. Inparticular, an emulator with a large number of workstationsis generally too costly for researchers to afford. Inthis paper, we present our experience in building a scalabledistributed network emulation system named"EMPOWER". EMPOWER provides the unique featureof precisely emulating multiple nodes with a single workstation,making it possible to support large network emulationwith a limited number of commodity computers.The paper describes some critical design issues such asthe system resource competition within an emulator nodeand its impact on the emulation of network throughputand packet delay. We present our methods to determinethe maximum number of virtual routers an emulator nodecan generate and some techniques to improve maximumthroughput and packet delay accuracy of an emulatornode. We believe such experiences are valuable for thestudy, design and implementation, performance tuning ofa variety of systems such as network emulators and highperformance host-based routers.