HOW broadcast GENERATED?

HOW broadcast GENERATED?

Posted by TechWorld on Tuesday, 7 January 2014 0

To communicate with all or part of the network, protocols use broadcast and multicast datagrams at Layer 2 of the Open Systems Interconnection (OSI) model. When a node needs to communicate with all of the network, it sends a datagram to MAC address 0xFFFFFFFF (a broadcast), which is an address to which the network interface card (NIC) of every host must respond. When a host needs to communicate with part of the network, it sends a datagram to address 0xFFFFFFFF with the leading bit of the vendor ID set to 1 (a multicast). Most NICs with that vendor ID respond to a multicast by processing the multicast to its group address.
Because switches work like bridges, they must flood all broadcast and multicast traffic. The accumulation of broadcast and multicast traffic from each device in the network is referred to as broadcast radiation.

Because the NIC must interrupt the CPU to process each broadcast or multicast, broadcast radiation affects the performance of hosts in the network. Most often, the host does not benefit from processing the broadcast or multicast---that is, the host is not the destination being sought, it doesn't care about the service that is being advertised, or it already knows about the service. High levels of broadcast radiation can noticeably degrade host performance.