Unicast, Multicast, Broadcast

Unicast, Multicast, Broadcast

Communication in network devices can be either of the three mentioned below:

  1. Unicast
  2. Multicast
  3. Broadcast

What is Unicast?

Unicast as its name represents Uni, means one. Thus in a Unicast type of communication, one computer or device can communicate to another device or computer. This communication happens between one sender and one receiver.

Unicast is done when the source device knows the address of the destination device.

Some examples of Unicast communication are:

1. Webpage browsing: When you open or access a website, the request from your computer goes to a particular server or website and the response also comes only to you. This communication happening between your browser client and the web server.

2. FTP Downloads: While to do any downloads from a ftp server, you request for some information and the information is only shared to you. Thus this is a type of Unicast communication.

What is Multicast?

Multicast means that traffic or communication is happening between one sender and many receivers. The receiver can be belonging to a particular group.  For device to receive the multicast traffic they join the group and this get the communication that is being transferred from the sender.

There are some protocols like OSPF; EIGRP that use special IP address ranges for multicast communication.

Some examples of multicast communication are:

1. WebEx Sessions: Sometimes you see that one of the training or some other sessions are conducted over WebEx, and people who want to listen or attend this session need to join the common group and they receive the communication that is being transmitted from the sender.

2. IP TV: IP TV is another example of Multicast communication

What is a Broadcast?

In Broadcast communication or traffic, the data from one sender is sent to all the other systems or devices in the network. The data is sent only once which is received by all the devices.

Network switches will forward broadcasts as it is by design and their functionality is as such. Routers are devices that do not allow broadcasts to pass through them. Thus any broadcast traffic that reaches the router will be dropped.

Examples of Broadcast are:

1. TV program broadcast: The TV programs that you see on a daily basis are broadcasts. It is sent to each TV receiver at residential places from the satellite and thus all receive the same information at the same time.

2. DHCP or ARP messages: There are some DHCP and ARP messages that are broadcasted in order to find some information for their proper functionality.  The ARP Request message and the DHCP Discover message are type of broadcast messages.

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