Broadcast Communication Model

The broadcast model is one in which a host sends to everyone on the subnet. ARP is not needed because the ethernet broadcast address is a well-known address with the value 0xFF FF FF FF FF FF (Broadcast IP addresses also exist and are covered in Chapter 2). In the unicast model, a host could send an IP packet to any host on any network (assuming we have a route to the destination host). In the broadcast model, the scope of the broadcast is the local subnet. Routers block broadcast traffic, so the scope of a broadcast is limited to the local subnet (see Figure 1-5).