2-2 
Figure 1-1 Unicast transmission 
Source
Receiver
Receiver
Receiver
Host A
Host B
Host C
Host D
Host E
Packets for Host B
Packets for Host D
Packets for Host E
IP network
 
 
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 
Figure 1-2.