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CSMA/CD Medium Access Control (MAC)

This is an algorithm (implemented in the network-card hardware) which defines how computers using Ethernet/802.3 can efficiently share a common medium: Carrier Sense, Multiple Access, with Collision Detection.
 
Multiple Access
 
All computers have equal access: there are no masters or slaves, etc. If the shared channel is clear (ie, not in use), a computer may begin to transmit immediately.
 
Carrier Sense
 
If the channel is busy, continue to "listen", and attempt to transmit as soon as it becomes available.
 
Collision Detection
 
If a collision is detected (ie, another computer started to transmit at the same time, so the signal is garbled), immediately cease transmission. Wait a random period of time, then start all over.

 
Lecture 14: Multiaccess Networks Copyright © 2005 P.Scott, La Trobe University Bendigo.


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