Broadcast networks have a single communication channel that is shared by all the machines on the network. Short messages, called packets sent by any machine are received by all the others. An address field within the packet specifies for whom it is intended. Upon receiving a packet, a machine checks the address field. If the packet is intended for itself, it processes the packet; if the packet is intended for some other machine, it is just ignored.
Some broadcast systems also support transmission to a subset of the machines, something known as multicasting. One possible scheme is to reserve one bit to indicate multicasting. The remaining (n-1) address bits can hold a group number. Each machine can “subscribe” to any or all of the groups. When a packet is sent to a certain group, it is delivered to all machines subscribing to that group.
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