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Multicast
Forwarding
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Routers must
know packet origination, rather than destination (opposite of unicast)
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... origination IP address denotes known
source
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... destination IP address denotes
unknown group of receivers
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Multicast routing utilizes Reverse Path
Forwarding (RPF)
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... Broadcast: floods packets out all
interfaces except incoming from source; initially assuming every host on
network is part of multicast group
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... Prune: eliminates tree branches
without multicast group members; cuts off transmission to LANs without
interested receivers
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... Selective Forwarding: requires its
own integrated unicast routing protocol
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