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Broadcasting on the Internet
Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.
It is possible on the Internet to mimic the kind of wide-audience news broadcasting that radio and television can achieve. A Web site simply maintains a list of subscribers and then sends news to those subscribers via e-mail on a regular basis. Thus, the Web site "broadcasts" news (or just about any kind of information). Webcasting is a technique of delivering messages to a wide audience.
The concept of Webcasting is taken even further with multicasting, which is a method of broadcasting that does not require that the source maintain a subscriber address list. Instead, packets are transmitted using a special multicast IP address. People who want to receive the broadcast set their Web browsers (or multicast receivers) to receive packets with the specific multicast address.
Another form of Web broadcasting called datacasting has recently emerged that does not even use the Internet as its delivery platform. Instead, a server broadcasts data over the VBI (vertical blanking interval) portion of the television signal. The VBI is normally used for closed captioning. Note that data broadcasting is a transmit-only model. Users cannot interact with the Web server, but the technique is useful for delivering specific types of content such as stock quotes, sports news, and so on. A company called WavePhore transmits data over PBS stations nationwide. All you need is a TV card in your computer to receive the transmissions.
Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.