Abstract: A video-on-demand (VoD) system comprises at least one server and a number of subscriber units connected to the server by way of a network (e.g. an ATM network). The server comprises a processing unit, data storage means for storing video data, and service supply means for responding to requests from subscribers by dispatching sequences of video data from said storage means over the network to said subscribers. The service supply means comprises a video application running in user space in the processing unit, and a VoD kernel I/O driver (VKID) running in kernel space in the processing unit, for reading data from said data storage means and dispatching the data to said network, in response to commands from the video application. Because the VKID is a kernel level module, it can perform this transfer quickly and efficiently, without the overhead of copying the data to and from user space.