OPTICODEC-PC INTRODUCTION
1-25
Multicast
In a multicast, a single stream is shared among the player clients. Although this tech-
nique reduces network congestion, it requires a network that either has access to
the multicast backbone (otherwise called the Mbone) for content generally distrib-
uted over the Internet, or is multicast-enabled for content distributed within a con-
tained private network. Multicast streams are sent directly to a group address, such
an IP multicast address, which many client computers can simultaneously access. The
users of a multicast have no control over the media content. Multicasts are an effi-
cient way to deliver the same material to a group of people over a LAN, as only one
copy of the stream is sent over the network.
Multicast uses RTP and UDP/IP. Multicast is not possible using HTTP or HTTP/ICY,
since it uses TCP/IP.
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Figure 1-10: Multicast
Relay Servers
A relay server is a specially configured streaming server that listens to an incoming
stream and then forwards the stream to one or more destination servers. A relay can
reduce network bandwidth consumption by load balancing the stream network traf-
fic or by separating unicast and multicast streams.
If the streaming server used supports it, Unicast and multicast can be used together
with relays to create larger network infrastructures. For example, a unicast stream
can be sent to a multicast server on a multicast enabled network. Alternatively, a
multicast stream can be sent to a local multicast enabled LAN, and the same stream
can be sent to the Internet as a unicast stream.
