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Unicasting

4 x 100Kbps simultaneous clients 

100Kbps

requires 

400Kbps

 connection 

from server

100Kbps

  Best choice for 

on demand media 

100Kbps

             Clients

  Each client gets a different 

stream, even if they are 

  Each client can 

100Kbps

watching the same movie

be given individual 

control over playback 

Media Server

  Heavier load (CPU and 

of on demand 

bandwidth) on server per client

content

Multicasting

4 x 100Kbps simultaneous clients 

requires 

100Kbps

 connection 

from server

  Best for live or

scheduled media 

100Kbps

Multicast

  Each client gets 

Router

the same stream

             Clients

  Conserves CPU 

processing power 

Media Server

  All clients playback 

and bandwidth

the same content 

at server

concurrently, with 

no end user control 

over playback

Multicasting is an excellent method for delivering the same content to multiple clients at the same time. 

The server sends only one data stream, whereas using unicast, the server must send a redundant stream 

for each connected client. So unicast results in a high server CPU load as well as increased network 

bandwidth demands at the server. Broadcast would solve the problem of duplicated streams, but would 

end up fl ooding the entire network, even if only a few end users wish to receive the content. 

Multicasting is only possible if both the streaming software and the network support it not all systems 

do. On the software side, the latest versions of the big three architectures Apple QuickTime, Microsoft 

namic Medianamic Media

Windows Media, and Realmedia do support multicasting. In terms of the network, to multicast over 

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an intranet, routers must be upgraded or replaced with multicast enabled devices. While this adds 

yet another expense to streaming implementation, for those organizations looking to reduce the high 

costs of training and/or other essential enterprise wide communications, the return on investment may 

be well worth the expenditure. Furthermore, multicasting can be used for a wide variety of other 

obe Dobe D

applications, in addition to streaming media.

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