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.

Real-time network services are designed to deliver real-time information with a high quality of service. Real-time information is live voice and video. Real-time services are designed to deliver real-time information in a timely manner.

The primary property of real-time information is that it must be delivered with a minimum amount of delay and with few dropped packets. However, if packets are lost, it does little good to recover them since the information is live streaming data. This is the opposite of mission-critical data, where every packet must get through without errors.

Because the data from a live source is continuous, it is often called "streaming media." Compression at the source and decompression at the destination is usually required  in order to provide timely delivery.

Usually, some amount of packet loss is acceptable, but delay is not. For example, if a few packets are lost, the listener or viewer might not even notice. In a video transmission, missing data appears as a very brief glitch. The receiver may compensate for lost data by filling in information or freezing a frame. In videoconferences, you will often see an image stay still for a moment. Software can compensate for lost data as well.

This topic continues under "Multimedia."

Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.
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