CSMA / CD Full Form

The full form of CSMA / CD is the Carrier Sense Multiple Access/Collision Detection. It is a MAC protocol used to detect collisions of signals in an Ethernet connection,when two or more devices are present.It uses Carrier sensing to detect the chance of collision in transmission and transmits only when no other stations are transmitting a Signal.CSMA CD helps in organizing data transmission by regulation of communication in a network.Once a Station detects a collision it will wait before transmitting next signal.CSMA-CD specifications have been standardized by the IEEE 802.3 standard,Institute of Electrical and Electronic Engineers is an organization of engineers from various fields.

What is CSMA-CD?

CSMA CD is a MAC protocol by which senses the signal transmission from all other stations in a Channel before transmitting the next signal.When many signals are transmitted simultaneously it will lead to collisions in the Channel, to avoid this CSMA/CD transmits a Jam Signal to stop transmission.

The wording meaning and role of each is as follows:

• CS- Carrier Sensing - Before sending any data the station will sense the carrier.Only if the carrier is free the station will transmit a Signal

• MA-Multiple access- A single channel will be accessed by multiple signals

• CD- Collision Detection- When 2 or more signals are transmitted at same time to a signal channel they will collide and cause problems in data transmission. Here collision detection is possible.

What is Ethernet Technology?

Ethernet is an old technology used to connect wired devices in an area by Local Area Network connection or wide area network (WAN).It is a network format that determines how the data is recognized,received and processed and transmitted to other devices in a network.

How does CSMA-CD technology work?

Algorithm for CSMA-CD is as follows:

• Check if the sender is ready to send data packets.

• When the signal is ready the transmission station waits until the channel is idle.

• The station waits until no signal is present in the channel ie:The channel is Idle.

• If the channel is ready without external signals the signal will be transmitted.

• Monitors for signal collision

• If a Collision is detected the channel will start collision resolution.

What is Collision Resolution?

When the station detects a collision in the transmission channel a Jam signal is produced to prevent further transmission of signals and notify all other stations.Retransmission signal is produced by stations. When the retransmission signals get aborted, the station waits for a backoff period before restarting the signal transmission.

What is a Jam Signal?

A signal that carries a bit pattern sent by a data station to inform the other stations that they must not transmit.

Characteristics of CSMA- CD

• It has carrier sense

• Once a collision is detected the station should wait for a random amount of time.

• A jam signal is used to indicate collision

• A higher transmission priority system is present

• It can initiate steps to resolve the collision.

Advantages of CSMA-CD

• Collisions can be detected in a very short time.

• Maximum of Bandwidth can be used for transmission.

• Wasteful transmission can be eliminated.

• Very Simple Algorithm

• It avoids collision

• It was invented for wireless connections

Disadvantages of CSMA/CD

• It is non scalable

• The Jam signal can lead to long waiting times.

• More Power Usage

• Network may not be available when required.

• Not suitable for long distance signal transmission.

• When Multiple devices are connected, the efficiency of collision detection is reduced.