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In WAN (Wide Area Network) or Internet, sometimes it's necessary to send the same copy of
data to multiple receivers (not all of the receivers in the network, which can then use broadcast).
If using unicast, the sender has to send one by one, it is becoming very inefficient when the
number of receivers increases, by consuming too much network resources and overloading
hosts and other devices. So multicast is becoming one of the main methods for
point-to-multipoint transmission when such applications like tele-conferencing, VOD (Video On
Demand), etc... are becoming popular.
An unicast example is shown in Figure6-1, which uses point-to-point communication; A multicast
example is shown if Figure6-2, which uses point-to-multipoint communication. Both of them are
sending the same data from A to B and C. So two copies of data are sent in Figure6-1, to B and
C, respectively; while only one copy is sent in Figure6-2.
Figure6-1. unicast example
Figure6-2. multiple example
The iSpirit 3026 switch supports IGMP (Internet Group Management Protocol), IGMP Snooping
and Layer 2 static multicast, all of them are used for providing multicasting services. IGMP is for
group management, but due to that the iSpirit 3026 switch is a Layer 2 switch, there is no
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