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    CSMA/CD (Carrier Sense Multiple Access / Collision Detection) is the protocol used in Ethernet networks to ensure that only one network node is transmitting on the network wire at any one time.

    Carrier Sense means that every Ethernet device listens to the Ethernet wire before it attempts to transmit. If the Ethernet device senses that another device is transmitting, it will wait to transmit.

    Multiple Access means that more than one Ethernet device can be sensing (listening and waiting to transmit) at a time.

    Collision Detection means that when multiple Ethernet devices accidentally transmit at the same time, they are able to detect this error.

    How Collisions Occur under CSMA/CD

    Imagine a very simple Ethernet network with only two nodes.

    Each node independently decides to send an Ethernet frame to the other node.

    Both nodes listen to the Ethernet wire and sense that no carrier is present.

    Both nodes transmit simultaneously, causing a collision.

    Both nodes detect the collision and each node waits a random amount of time before transmitting again.

    Collisions are normal on an Ethernet network. A small amount of collisions are expected in the protocol design.

    If too many nodes are transmitting on an Ethernet network, the number of collisions can rise to an unacceptable level. This can reduce the amount of available bandwidth on an Ethernet network because so much bandwidth is lost in retransmission.

    Ethernet switches greatly reduce the already minor difficulties experienced with the CSMA/CD protocol.

    • jason polydor

      Its a simple explanation, very instructive. thanks

    • shakil

      I understood it clearly. Thank u for the explanation.

    • Dang Nguyen

      great, thanks! 😉

    • Tan Cong

      It’s really good. Thanks 🙂

    • Suvadip

      its really helpful man, thanks a lot. 😆 😆 😆

    • Dhaval Vithalani

      it is really too helpfool…Thanks a lot..

    • Murugesh_CIT_India

      good but further more detail is required… for ex: how does the station listens to the channel and how does it know the channel is busy or used… and what kind of jamming error is woken

    • subardhan

      good explanation , very helpful thanks…..

    • amit

      it is very simple explain

    • arindam bhattacharjee

      Thanx a lot for sharing

    • Andy

      Thanxx…a lot it was easy to understand!!!!

    • samuel

      good but differentiate with cs ma/ca

    • kd & Ph

      thanks dude good explanation

    • saikrishnan

      that was quite easy to understand ! 

    • matacha

      unless CSMA/CA, CSMA/CD sends signals after collision had occured. What are other differences?

    • Mukesh Joshi

      The explanation was in very simple words but was very good.

    • prateek

      but i need more deeply information

    • aanchal

      i also need more information……

    • Zahid

      Please tell me how a node listens to the medium that its free or not? or take it as ..how a node detects a carrier on the ethernet wire ? Please reply soon.

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