Measuring the Performance of a Distributed Quota Enforcement System for Spam Control

J.D. Zamfirescu
Massachusetts Institute of Technology, Cambridge, MA,

In this thesis, I evaluate Distributed Quota Enforcement (DQE), a system for enforcing quotas on e-mail use as a spam control mechanism. I briefly describe the design and implementation of DQE, and then evaluate the enforcer’s performance in several ways. My evaluation includes: the capacity of a single node; how the enforcer scales with added nodes; how well the enforcer tolerates faults; the relationship between the enforcer’s size and time to respond (request latency); and the impact of globally distributing the enforcer’s nodes.

Salient features of the evaluation include: an enforcer composed of a few thousand high-end PCs can handle the world’s current e-mail volume; the enforcer is resistant to failures: even with 20% of its nodes down, stamps are reused on average only 1.5 times; the main bottleneck in the enforcer’s performance is disk seeks.

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