CSMA\CD
CSMA\CD or Carrier Sense Multiple Access/Collision Detection is a media access and control method used in computer networks.
In CSMA\CD, different stations agree on some terms and collision detection measures for effective transmission.
How does CSMA\CD work?
- First, it is checked if the sender is ready to send data packets.
- Then, the sender keeps checking if the transmission link is idle. To check it, transmissions from other nodes are continuously sensed. Meaning, if it senses the carrier is free and it has no collisions, then only it sends the data.
- But, if during transmission a collision occurs, then the transmission is stopped. A jam signal is transmitted onto the link and it waits for some time before reattempting to send the frame.
- Finally, if no collisions are experienced, the sender completes the transmission of the frames and resets the counters.
The algorithm of collision resolution
The algorithm of collision resolution is as follows:
- The station continues the transmission of the frame for a specific amount of time, to ensure all the other stations detect collision.
- It increments the retransmission counter.
- After the maximum number of attempts for transmission is reached, the transmission is aborted.
This algorithm is only useful to detect collisions but does not help in decreasing the number of collisions. It is also not very useful for large networks, as the performance decrements when the number of stations increases.