Functionality
Download and streaming video on demand systems provide the user with a large subset of VCR functionality including pause, fast forward, fast rewind, slow forward, slow rewind, jump to previous/future frame etc. These functions are called trick modes. For disk-based streaming systems which store and stream programs from hard disk drive, trick modes require additional processing and storage on the part of the server, because separate files for fast forward and rewind must be stored. Memory-based VOD streaming systems have the advantage of being able to perform trick modes directly from RAM, which requires no additional storage or CPU cycles on the part of the processor.
It is possible to put video servers on LANs, in which case they can provide very rapid response to users. Streaming video servers can also serve a wider community via a WAN, in which case the responsiveness may be reduced. Download VOD services are practical to homes equipped with cable modems or DSL connections. Servers for traditional cable and telco VOD services are usually placed at the cable head-end serving a particular market as well as cable hubs in larger markets. In the telco world, they are placed in either the central office, or a newly created location called a Video Head-End Office (VHO).
Read more about this topic: Video On Demand