Web Design in a Nutshell, 3rd Edition

Server Software and Protocols

True streaming relies on special server software that permits the uninterrupted flow of data. The information in the song is broken up into little “packets” and sent out in order over the lines. These packets are then reassembled on the user’s end. The audio player collects a number of packets before playback begins (a process called buffering ) to increase the likelihood of smooth playback.

Streaming media takes advantage of UDP (User Datagram Protocol) , RTSP (RealTime Streaming Protocol) , or RTP (RealTime Transfer Protocol) for the transmission of data. What makes these protocols effective at streaming is that if a packet of information is dropped or missing, the data transmission continues without it. This is in contrast to HTTP, the traditional protocol of the Web, which stops and tries to resend lost packets, potentially halting the stream.

UDP was the first protocol used for streaming media because of its improvements over HTTP. The newer RTSP is more efficient than UDP. RTSP is a two-way streaming protocol, allowing the user to send messages back to the server (such as rewinding the tape). By contrast, RTP (used by Apple QuickTime) is a one-way stream (similar to HTTP in this regard), only the file never downloads completely to the user’s hard drive as it does in HTTP or FTP transfers.

Commercial streaming server software such as Windows Media and Helix Server can handle thousands of simultaneous streams. It provides robust administrative tools ...