What is the CSMA/CD network protocol?

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) is a network protocol for carrier transmission that operates at the MACmedium access control layer.

When a collision is identified, the CSMA/CD quickly terminates the transmission by sending a signal, saving the sender's time to send the data packet. Let's say each station detects a collision as the packets are transmitted. In such a situation, the CSMA/CD immediately issues a jam signalThis informs the stations about the collision and not to send any data.   to halt the transmission and delays sending another data packet until a random time has passed. When a free channel is discovered, the data will be sent.

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Workflow

The following illustration builds a comprehensive understanding of the workflow mechanism of CSMA/CD:

Algorithm

• The station that intends to transmit the data detects if the carrier is available or busy by perceiving its state. If a carrier is empty, the transmission starts.
• The condition $T_t >= 2 * T_p$, where $T_t$ is the transmission delayIt is the time taken to put the packet on the link. and $T_p$ is the propagation delayIt is the time required to reach the destination after the signal has been sent., is used by the transmission station to identify collisions.
• As soon as it notices a collision, the station sends the jamming signal.
• Following a collision, the transmitting station interrupts transmission and waits for a predetermined period, known as the "back-off time". The station then re-transmits the signal.

Efficiency

Although CSMA/CD is more efficient than CSMA, a few considerations are discussed below relating to its effectiveness:

• The efficiency of CSMA/CD decreases with increase in distance.
• Even if efficiency improves with a larger packet size, there is still a limit as to how it can be. The packets can only be a maximum of 1500 bytes long.

Advantages

The following points discuss the advantages of using CSMA/CD:

• For collision detection, CSMA/CD is better than CSMA.
• It is used for quick collision detection on a shared channel.
• Compared to CSMA/CA, it has lesser overhead.
• Using CSMA/CD helps prevent the waste of transmission in any way.
• Whenever mandatory, it consumes or shares all of the bandwidth.

Disadvantages

Disadvantages are given as follows:

• After reaching the maximum distance, collision detection is impossible.
• Not ideal for larger networks as collision detection is difficult to detect.
• The performance gets considerably disrupted when more devices are added.