In our CSMA/CD model we used a couple of terms that we need to define further and the first term is to "BROADCAST packets".

Broadcasts are really exactly what the name implies. It 's a broadcast - for example, KFM Radio is broadcast radio, it doesn't know who is receiving the signal but the radio station still broadcasts the signal. If you turn your radio on, you hear it. If you turn it off, you don't.

Broadcast packets are similar in that a workstation, server or network interface card will broadcast to every workstation on that network, and part of the Ethernet 's job is that if it hears a broadcast, it must hear that broadcast.

The next concept is the concept of "UNICAST".

UNICAST 's are packets where one workstation is talking directly to another. If you are going to have a conversation on the telephone, you're having the UNICAST conversation. Well, provided it's not a conference call.

You're having a UNICAST conversation because you are talking directly to the person on the opposite side.

The final term we used is "MULTICAST".

That would be the equivalent to a conference call as mentioned above where there are a number of recipients who are tuned into that conversation.

Essentially, the distinction between these is the fact that Broadcasts are very noisy, in other words, when I start broadcasting, I hold the loud hailer up and I start calling the odds. Nobody has got any opportunity to talk back to me.

When I have a UNICAST or MULTICAST conversation, it 's a conversation, I'm talking to a client(s), and the client(s) is talking to me.

The same happens on a network and let 's look at a couple of examples.

Broadcast services are noisy. That is, the more broadcast services you have on your network, the less opportunity you have of talking in a UNICAST manner - between client and client, client and server or server and server.

So Broadcast 's aren't desirable to have on your network in large volumes. You will need to use them, but it 's important to realize that broadcasting on the network is far from optimal. A candidate that is particularly prone to generating large volumes of broadcast traffic is the process of master browser selection in a Windows network.