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.
