Optical Burst Switching (OBS) has been proposed as a candidate technology for the next-generation Internet. In OBS, packets are assembled into a burst, and a burst control packet is sent in advance to inform and reserve resources at the optical nodes in the path of the burst. In this study, we analyze the horizon-based reservation scheme in OBS using Markov fluid queues. First, we provide a solution to continuous feedback Markov fluid queues, then we model the horizon-based reservation scheme as a continuous feedback Markov fluid queue and numerically study it. We provide numerical examples to validate our model and its solution technique as well as to obtain some insight on the horizon-based reservation mechanism. © 2013 IEEE.