The future prospects of Optical Burst Switching (OBS) architectures depend on several crucial factors, such as their performance versus their complexity and implementation cost. This paper presents a framework for evaluating the performance of OBS networks, comprising an analytic performance model and a network simulator. The framework is used for evaluating the performance of several different network topologies and the analytic evaluation model is validated by the simulation results. Two resource reservation mechanisms for burst transmission, the Just Enough Time (JET) mechanism, and a centralized mechanism, are examined using the performance evaluation framework. It is shown that the lack of awareness of global state information, characteristic of the JET mechanism, only significantly hampers the performance of OBS networks if limited range wavelength conversion is deployed in the network.