Collision Domain and Broadcast tutorial.../

Collision Domain and Broadcast 

Domain in Computer Network

1. Collision Domain –
                   A Collision Domain is a scenario in which when a device sends out a message to the network, all other devices which are included in its collision domain have to pay attention to it, no matter if it was destined for them or not. This causes a problem because, in a situation where two devices send out their messages simultaneously, a collision will occur leading them to wait and re-transmit their respective messages, one at a time. Remember, it happens only in case of a half-duplex mode.

2. Broadcast Domain –
           A Broadcast Domain is a scenario in which when a device sends out a broadcast message, all the devices present in its broadcast domain have to pay attention to it. This creates a lot of congestion in the network, commonly called LAN congestion, which affects the bandwidth of the users present in that network.

From this, we can realize that more the number of collision domains and more the number of broadcast domains, the more efficient is the network providing better bandwidth to all its users.

• HUB – it neither breaks a collision domain nor a broadcast domain,i.e a hub is neither a collision domain separator nor a broadcast domain separator. All the devices connected to a hub is in a single collision and single broadcast domain. Remember, hubs do not segment a network, they just connect network segments.

• SWITCH – Every port on a switch is in a different collision domain, i.e a switch is a collision domain separator. So messages that come from devices connected to different ports never experience a collision. This helps us during designing networks but there is still a problem with switches. They never break broadcast domains, means it is not a broadcast domain separator. All the ports on the switch are in still in a single broadcast domain. If a device sends a broadcast message, it will still cause congestion.

• ROUTER – A router not only breaks collision domains but also break broadcast domains, means it is both collision as well as broadcast domain separator. A router creates a connection between two networks. A broadcast message from one network will never reach the other one as the router will never let it pass.