3Com 4210G Series Configuration Manual page 340

Figure 1-1 Unicast transmission
Source
Packets for Host B
Packets for Host D
Packets for Host E
Assume that Host B, Host D and Host E need the information. A separate transmission channel needs
to be established from the information source to each of these hosts.
In unicast transmission, the traffic transmitted over the network is proportional to the number of hosts
that need the information. If a large number of users need the information, the information source
needs to send a copy of the same information to each of these users. This means a tremendous
pressure on the information source and the network bandwidth.
As we can see from the information transmission process, unicast is not suitable for batch
transmission of information.
Broadcast
In broadcast, the information source sends information to all hosts on the subnet, even if some hosts
do not need the information, as shown in
IP network
Receiver
Figure
2-2
Host A
Receiver
Host B
Host C
Receiver
Host D
Host E
1-2.