Hybrid admission control algorithm for multimedia server

Abstract

A multimedia server has to serve a large number of clients simultaneously. Given the real-time requirements of each client and fixed data transfer bandwidth of disks, a multimedia server must employ admission control algorithms to decide whether a new client can be admitted without violating the service requirements of the clients already being served. The main goal of admission control algorithm is to accept enough traffic to efficiently utilize server resources, while not accepting clients whose admission may lead to the violations of the service requirements of clients. In this thesis we are proposing a hybrid admission control algorithm that can handle a larger number of clients simultaneously. One interesting feature of this algorithm is different admission techniques for different clients based on their service requirements. The performance of hybrid admission control algorithm is dependent on the diskscheduling algorithm. Most of the conventional disk-scheduling algorithms have addressed this problem of optimizing total seek time and they completely ignore the rotational latency. In this thesis we demonstrate a new disk scheduling technique named near optimal disk scheduling algorithm that derives a sequence of accessing media blocks from disks so as to minimize both seek time and rotational latency incurred during retrieval. In order to .provide continuous retrieval of each media stream, we have to ensure that service time is less than minimum duration of a round. Since the service time is a function of the number of blocks and their relative positions on the disk, it may exceed the minimum duration of a round. We refer to such rounds as overflow rounds. In hybrid admission control algorithm we can restrict overflow rounds within the limit by adjusting some parameters of the algorithm. The near optimal disk scheduling algorithm as well as the technique for minimizing overflow of rounds presented in this thesis significantly improves the performance of the hybrid admission control algorithm. We have demonstrated the effectiveness of the hybrid admission control algorithm and the near optimal disk-scheduling algorithm through extensive simulation.