Rights Creative Commons: Attribution 3.0 Hong Kong License A Shared Buffer Architecture for Interactive VOD Servers*

Video-on-demand ( V O D) servers need to be efficiently designed i n order to support a large number of users viewing the same or different videos at different rates. While consid-ering a disk-array based V O D server, use of a shared buffer at the server end m a y be more economical than the sole use of dedicated buffers a t each user’s end. I n this paper, we propose a simple buf fer sharing architecture that may be used when disk-array based video servers are used. Our a im is t o support the max imum number of users fo r a given num-ber of video server disks while employing a simple scheme requiring less buffer space. The number of video segment retrievals that can occur within a certain t ime (the service round) is max imum when the scan disk scheduling algorithm is used. Consequently, we shall assume use of the scan algo-rithm for disk retrieval. T h e V O D server has a buffer man-ager that directs retrieved segments to appropriate buffer locations depending o n their release and deadlines. The re-lease and deadlines of segments are such that buffer require-men t at the user’s set-top box is minimized to two video seg-ments while avoiding video starvation and buffer overflow at the user‘s end. W e propose a novel scheme for the op-eration of the shared buffer that aims at increasing buffer utilization and decreasing cell loss due to buffer overflow. An ATM based broadband network is assumed and all seg-ments are stored i n buffers as fixed length A T M cells.