Collision and Broadcast domains

Collision and Broadcast domains

Collision Domain:

As the name indicates, the domain where a collision of packets occurs is called as the collision domain.

A network connected with the help of Hub is a good example of collision device. If two or more devices connected to the hub transfers data at the same time, a collision of data occurs. So in a collision domain when one device transmits data, the others must listen or else it leads to data loss due to the collision. Then both the devices have to retransmit the data after some time.

Whereas when a switch is used instead of a hub, it separates single large domain created by hub into multiple small collision domains. The switch creates separate collision domain for each of its port. This reduces chances of occurrence of collision when two or more devices transmit data at the same time. Collision domains use half-duplex mode of communication. Connecting devices using bus topology also leads to a collision domain as bus topology supports only half duplex communication.

 As the number of collisions increase, the performance of the network decreases. This is because the hosts spend most of their time in re-transmitting the data that is lost due to the collision. As hubs are outdated, no more used in the networks, chances of collision have been reduced to a greater extent.

Broadcast Domain:

The communication technique in which data is sent to all the devices that are connected in the network is called as Broadcast. This is similar to that of sending message or email to all the contacts.

All the devices in this domain can transmit data among themselves without having a routing device. The communication is possible by sending a frame with the broadcast address of the network. Local area networks are the best examples of broadcast domains.  Hubs and switches do not switch broadcast data. All the devices that are connected to the either switch or hub are considered to be in the single broadcast domain.

The Router separates all the broadcast domains present in the network. Router does not allow broadcast message from one network to enter into another network. The router creates a separate broadcast domain for all the devices that are connected to each of its ports.

As the number of devices in a broadcast domain increases, the available bandwidth to each device also decreases. All the devices in the broadcast domain share the same bandwidth. All the devices have to process the broadcast messages; the overall performance of network reduces to an extent.

Collision and Broadcast domains effects networks, hence proper care must be taken to reduce the effects while designing the network itself

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