Resource reservation has been recently supported by many real-time operating systems to provide applications with guaranteed and timely access to system resources. Typically, reservations are based on the worstcase requirements, and therefore can inflate resource demands unnecessarily. Many multimedia applications such as MPEG video streams (1) have high worst-case to average-case demand ratio and (2) can tolerate some deadline misses. To support such applications, we propose a “multi-granularity” reservation model. Instead of the classical {C, T, D} model of resource reservation, the multi-granular reserve specification is given by {{C, T, D}, . . . , {Cx , x Ti}, . . . , {Cy , y Ti}} which represents a guarantee of the highest-granularity reserve for C units of resource during every successive periodic interval of T only as long as the resource usage by each of its low-granularity reserves (e.g., Cx units of resource in every recurring time of x Ti, x ∈ Z+ ) is maintained. T...