Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Chapter 253
Addressing Type Review

The example given in the preceding section is simple, but very real. However, there are many applications today that require a one-to-many or many-to-many type of transmission and reception (e.g., audio and video, stock ticker, workgroup applications, electronic whiteboards, etc.). All of these applications can have one or more senders and one or more receivers. In IPv4, there are three types of addresses:

Unicast: A unique address that allows one host to receive a datagram.

Broadcast: An address that allows every host to receive a datagram.

Multicast: An address that allows a specific group to receive a datagram.

Unicast is the ability to uniquely identify a host on a subnet or internet. The transmission and reception is accomplished in a one-to-one relationship. A broadcast address is exactly that: An address that is received by every host on the subnet. Routers (with exceptions like DHCP and BOOTP) will not forward datagrams that have a local broadcast address. A multicast address is one that allows a specific group of hosts to receive a datagram, while all others ignore the datagram. For this conversation, we will stay with multicasting as it applies to the IP protocol.