Carrier Sense Multiple Access and Collision Detection (CSMA/CD)




It is an approach used in the local area networking by the early Ethernet technology. CSMA is a network protocol that detects the network signals before transmission of any information on the carrier. Its execution is usually carried out by several connected devices.




Any device can make attempts anytime to transmit a frame. The sensing of the devices will depend on how free the line will be and determines if it will be utilized during the transmission.

A collision occurs in situations where other devices attempted to convey the data at a similar period and hence the frames will be expelled. Once this problem arises, each of the device will wait to retransmit the data at a random time. This process is repeated until it reaches a point where the transmission becomes successful.

Therefore the CSMA/CD will determine the response of the network devices in a situation where a data channel is being accessed by two devices at the same time. All active stations taking part in the process are able to detect a collision. The random time interval is usually heightened in a situation where the collision occurs for the second time.

This happens depending on the number of times it happens and thus will be increased gradually till the transmissions become successful.

The Collision Detection (CD) is useful in [providing a response in case the collision occurs. The network internet card will check its own transmission if the data is in awaiting o be conveyed. The transmission will be terminated immediately once it detects the collision.

To solve this occurrence, it will channel a 32-bit jam sequence to ensure that other nodes that are receiving the frame at the same get the signal. The remaining end nodes will get rid of the frame as a result of the error.

The CSMA creates a minimum limit of the frame size to ensure the process of transmission becomes successful and that chances of collision are minimized. One of the main restrictions is that the frames should have more than 46 bytes of payload.

This frame size is associated with the type of media and length of the span of network. The number of repeaters are also considered while determining the size of the frame. It encompasses the passage of signals to the far end of the Local area network.

A higher medium utilization contributes to an improved performance of the Carrier Sense Multiple Access. In the recent technology, collisions have been reduced by a larger extent the fact that Ethernet allowed for the formation of full duplex and point to point channels between the source and the receiver.

CSMA/CD is more efficient in the earlier versions of Ethernet hubs which are still in existence. CSMA/CD is a MAC layer protocol while the Ethernet is meant to be a data link protocol.

The two ways in which the occurrences of a collision can be avoided is when the detection is initiated by the CSMA/CD and can also be avoided by the CSMA/CA.




These collisions can be prevented from happening the fact that the individual nodes provide their intentions to convey the data before executing the process. Though the avoidance technique is known to reduce performance because of the excessive overhead.