Saturday, February 7, 2009

Directed Broadcast Address

Sometimes,it is convenient to send a copy of a packet to all hosts on a physical network.To make broadcast easy,IP defines a directed broadcast address for each physical network.When a packet is sent to network's broadcast address,a single copy of the packet travels across the internet until it reaches the specified network.The packet is then delivered to all the hosts on the network.The directed broadcast address for a network is formed by adding a suffix that consists of all 1 bits to the network prefix.

To ensure that each network can have directed broadcast address,IP reserves the host address that contains all 1 bits.An administrator must not assign the all ones host address to a specific computer or the software may malfunction.If a network hardware supports broadcast,a directed broadcast will be delivered using the hardware broadcast capability.In such cases,transmission of the packet will reach all computers on the network.When a directed broadcast is sent to a network that does not have hardware support for broadcast,software must send a separate copy of the packet to each host on the network.

No comments: