Carrier sense multiple access with collision detection (CSMA/CD) is the opposite of CSMA/CA. Instead of detecting data to transmit signal intention to prevent a collision, it observes the cable to detect the signal before transmitting.

Collision detection means that when a collision is detected by the media access control policy, transmitting by the network stations stops at a random length of time before transmitting starts again. It is faster than CSMA/CA as it functions in a network station that involves fewer data frames being transmitted. CSMA/CD is not as efficient as CSMA/CA in preventing network collisions. [1]

Figure 1. Carrier sense multiple access with collision detection (CSMA/CD)

Figure 1 shows similar is the process of CSMA/CD, where the data packet transmission is only done when the data transmission medium is free. When various network devices try to share a data channel simultaneously, then it will encounter a data collision.

The medium is continuously monitored to detect any data collision. When the medium is detected as free, the station should wait for a certain time period before sending the data packet to avoid any chances of data collision. When no other station tries to send the data and there is no data collision detected, then the transmission of data is said to be successful. [2]

Algorithms

The algorithm of CSMA/CD is:

• When a frame is ready, the transmitting station checks whether the channel is idle or busy.
• If the channel is busy, the station waits until the channel becomes idle.
• If the channel is idle, the station starts transmitting and continually monitors the channel to detect collision.
• If a collision is detected, the station starts the collision resolution algorithm.
• The station resets the retransmission counters and completes frame transmission. [3]

CSMA/CD is one such technique where different stations that follow this protocol agree on some terms and collision detection measures for effective transmission. This protocol decides which station will transmit when so that data reaches the destination without corruption. [4]

References:

1. https://www.getkisi.com/blog/media-access-control
2. https://www.softwaretestinghelp.com/what-is-csma-cd/
3. https://www.tutorialspoint.com/csma-with-collision-detection-csma-cd
4. https://www.geeksforgeeks.org/collision-detection-csmacd/

Cite this article:

Gokula Nandhini k (2023), Carrier sense multiple access with collision detection (CSMA/CD), AnaTechmaz, pp.92