Admissions control and data placement for VBR video servers

In this paper we compare techniques for storage and real-time retrieval of variable bit rate (VBR) video data for multiple simultaneous users. We compare two main classes of data placement techniques: constant time length (CTL) and constant data length (CDL). For each technique, we consider both deterministic and statistical admissions control policies and show that the statistical policies are more suitable for interactive applications. CDL-based data placement is shown to be able to achieve lower overload probabilities than CTL-based ones for a given user distribution at the expense of a much higher buffer requirement and higher delays. A “burst mode” technique for CDL is discussed that can reduce the delays at the expense of even higher buffer usage. We verify our theoretical overload probabilities for the statistical admissions control policies with experiments run on a discrete event simulator