3.1.3 Streaming

Audio files tend to be relatively large. It is inconvenient to have to transmit an entire file because an audio source can be played. This is why many audio providers use a technique called streaming.

Streaming is a technique by which the content of a file is sent serially. However, the receiver does not wait until the entire file is received before playing the content. Streaming requires both the server (content provider) and client (content player) understand the same streaming protocol.

Several protocols are commonly used for content streaming. The Real-time Transport Protocol (RTP) uses both user datagram protocol (UDP) and transport/control protocol (TCP) to accomplish streaming. However, the Real Time Streaming Protocol (RTSP) and the Real Time Control Protocol (RTCP) only use UDP.

Because UDP is connectionless, streaming protocols using UDP are often blocked by firewalls, including common residential gateways. That's why some streaming servers use standard HTTP for streaming. Icecast is a open source implementation of a streaming protocol. It is, in part, a reimplementation of a proprietary streaming server called SHOUTcast .

Audio streaming is commonly used by online "radio stations" to broadcast live programs and recorded programs. It can also be used for schools to broadcast lectures online.