Non-intrusive estimation of Web server delays

We introduce a novel passive network monitoring architecture which enables us to capture and integrate data from different levels of the protocol stack using a probe which can be placed at any arbitrary point in the network. We subject the data gathered to off-line analysis and show how, by modelling the dynamics of the protocols observed, we are able to extract information which would not be available using existing means. We show how the technique can be used to passively measure Web server response latency. Experiments are described which use artificially generated loads to validate the techniques used, and results obtained from the observation of real traffic are presented.