Are you an EPFL student looking for a semester project?
Work with us on data science and visualisation projects, and deploy your project as an app on top of Graph Search.
Concept
Carrier-sense multiple access with collision detection
Summary
Carrier-sense multiple access with collision detection (CSMA/CD) is a medium access control (MAC) method used most notably in early Ethernet technology for local area networking. It uses carrier-sensing to defer transmissions until no other stations are transmitting. This is used in combination with collision detection in which a transmitting station detects collisions by sensing transmissions from other stations while it is transmitting a frame. When this collision condition is detected, the station stops transmitting that frame, transmits a jam signal, and then waits for a random time interval before trying to resend the frame.
CSMA/CD is a modification of pure carrier-sense multiple access (CSMA). CSMA/CD is used to improve CSMA performance by terminating transmission as soon as a collision is detected, thus shortening the time required before a retry can be attempted.
With the growing popularity of Ethernet switches in the 1990s, IEEE 802.3 deprecated Ethernet repeaters in 2011, making CSMA/CD and half-duplex operation less common and less important.
The following procedure is used to initiate a transmission. The procedure is complete when the frame is transmitted successfully or a collision is detected during transmission.
Is a frame ready for transmission? If not, wait for a frame.
Is medium idle? If not, wait until it becomes ready.
Start transmitting and monitor for collision during transmission.
Did a collision occur? If so, go to collision detected procedure.
Reset retransmission counters and complete frame transmission.
The following procedure is used to resolve a detected collision. The procedure is complete when retransmission is initiated or the retransmission is aborted due to numerous collisions.
Continue transmission (with a jam signal instead of frame header/data/CRC) until minimum packet time is reached to ensure that all receivers detect the collision.
Increment retransmission counter.
Was the maximum number of transmission attempts reached? If so, abort transmission.
About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.