This paper introduces the buffer-based request/reply (RQRP) Pull delivery m
odel, which has been accepted by the digital audio-visual council (DAVIC) f
or the delivery of audio-video stream in video on demand (VoD) systems [DAV
IC, Jitter Concealment Tool, DAVIC 1.5 baseline document 15z07r40]. A VoD s
ystem has been successfully developed and the performances of two variation
s of the RQRP protocol, namely half-duplex and full-duplex modes have been
evaluated. Simulation study of the performance was initially carried out on
the RQRP protocol. A prototype VoD system using the RQRP protocol specific
ation was implemented and the experiment results were obtained. The investi
gation shows that the full-duplex RQRP yields better results, especially ov
er high delay networks, in terms of maximum throughput, rate of adapting to
client play-out rate changes and shorter start-up time. (C) 2000 Elsevier
Science B.V. All rights reserved.