A collision domain is a physical network segment where data packets can collide with one another when being sent on a shared medium, in particular, when using the Ethernet networking protocol. A network collision occurs when more than one device attempts to send a packet on a network segment at the same time. Collisions are resolved using carrier sense multiple access or a variant thereof in which the competing packets are discarded and re-sent one at a time. This becomes a source of inefficiency in the network.[1]
This situation is typically found in a hub environment where each host segment connects to a hub that represents only one collision domain and only one broadcast domain. Collision domains are also found in wireless networking such as Wi-Fi. Only one device in the collision domain may transmit at any one time, and the other devices in the domain listen to the network in order to avoid data collisions. Because only one device may be transmitting at any one time, total network bandwidth is shared among all devices. Collisions also decrease network efficiency on a collision domain; if two devices transmit simultaneously, a collision occurs, and both devices must retransmit at a later time.
To relieve the network of collision domains, it is recommended to use a network switch which increases the number of collision domains while decreasing each collision domain's size. This is because each port on a switch is its own collision domain.A broadcast domain is a logical division of a computer network, in which all nodes can reach each other by broadcast at the data link layer. A broadcast domain can be within the same LAN segment or it can be bridged to other LAN segments.
In terms of current popular technologies: Any computer connected to the same Ethernet repeater or switch is a member of the same broadcast domain. Further, any computer connected to the same set of inter-connected switches/repeaters is a member of the same broadcast domain. Routers and other higher-layer devices form boundaries between broadcast domains.
This is as compared to a collision domain, which would be all nodes on the same set of inter-connected repeaters, divided by switches and learning bridges. Collision domains are generally smaller than, and contained within, broadcast domains.
While some layer two network devices are able to divide the collision domains, broadcast domains are only divided by layer 3 network devices such as routers or layer 3 switches.
This situation is typically found in a hub environment where each host segment connects to a hub that represents only one collision domain and only one broadcast domain. Collision domains are also found in wireless networking such as Wi-Fi. Only one device in the collision domain may transmit at any one time, and the other devices in the domain listen to the network in order to avoid data collisions. Because only one device may be transmitting at any one time, total network bandwidth is shared among all devices. Collisions also decrease network efficiency on a collision domain; if two devices transmit simultaneously, a collision occurs, and both devices must retransmit at a later time.
To relieve the network of collision domains, it is recommended to use a network switch which increases the number of collision domains while decreasing each collision domain's size. This is because each port on a switch is its own collision domain.A broadcast domain is a logical division of a computer network, in which all nodes can reach each other by broadcast at the data link layer. A broadcast domain can be within the same LAN segment or it can be bridged to other LAN segments.
In terms of current popular technologies: Any computer connected to the same Ethernet repeater or switch is a member of the same broadcast domain. Further, any computer connected to the same set of inter-connected switches/repeaters is a member of the same broadcast domain. Routers and other higher-layer devices form boundaries between broadcast domains.
This is as compared to a collision domain, which would be all nodes on the same set of inter-connected repeaters, divided by switches and learning bridges. Collision domains are generally smaller than, and contained within, broadcast domains.
While some layer two network devices are able to divide the collision domains, broadcast domains are only divided by layer 3 network devices such as routers or layer 3 switches.
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