This paper introduces approximate analytical models to evaluate the performance of end-to-end measurement based connection admission control (EMBAC) mechanisms, devised for the setup of real time flows over the Internet. These mechanisms rely on users probing the current congestion status of their required network path using a succession of probing packets. If the probing rate measured at the end receivers is greater than a certain threshold, users are allowed to switch to a phase of data exchange; otherwise they abort the call setup attempts. In conformance with the differentiated services framework, routers are oblivious to individual flows, and only need to give higher priority to data packets than to probing traffic. Despite the approximations introduced to make the analysis tractable, our model appears to be extremely accurate for a scenario of constant rate connections. Much less accurate, but useful as a possible starting point for future work, is the extension of the model to a scenario of variable rate connections. Simulation results are also presented in the paper to gain additional quantitative insights on the effectiveness of EMBAC to provide support for tight QoS requirements.
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