Multicast Versus Unicast. Apple Power Mac M5456, QuickTime Streaming Server

LL0329.book Page 10 Wednesday, November 20, 2002 2:09 PM

Multicast Versus Unicast

QTSS and DSS support both multicast and unicast network transport to deliver streaming media.

In a multicast, a single stream is shared among the clients (see illustration). Each client “tunes in” to the stream much as a radio tunes in to an FM broadcast. Although this technique reduces network congestion, it does require a network that either has access to the multicast backbone, otherwise called the Mbone, for content generally distributed over the Internet, or is multicast enabled for content distributed within a contained private network.

Multicast

In a unicast, each client initiates its own stream, resulting in the generation of many one-toone connections between client and server (see illustration). Many clients connected via unicast to a stream in a local network can result in heavy network traffic. But this technique is the most reliable for delivery over the Internet since no special transport support is required.

Unicast

10 Preface