How to Emulate Web Traffic Using Standard Load Testing Tools
  Conventional load-testing tools are based on a fifty-year old time-share computer paradigm where a finite number of users submit requests and respond in a synchronized fashion. Conversely, modern web traffic is essentially asynchronous and driven by an unknown number of users. This difference presents a conundrum for testing the performance of modern web applications. Even when the difference is recognized, performance engineers often introduce modifications to their test scripts based on folklore or hearsay published in various Internet fora, much of which can lead to wrong results. We present a coherent methodology, based on two fundamental principles, for emulating web traffic using a standard load-test environment. 
James F. Brady and Neil J. Gunther
cs.PF cs.NI