Explain about CSMA/CD

It is an access method used mainly with LANs configured in a bus topology. With CSMA/CD, any station (node) can transmit a message to any other  station  (or  stations)  as  long  as  transmission  medium  is  free  of transmissions  from  other  stations.  Stations monitor (listen to) line to determine if line is busy. If the station has a message to send though the line is busy, it waits for an idle condition before sending its message. If two stations transmit at the same instance, a collision takes place. When this happens, station  first  sensing  the   collision  sends  a  special  jamming  signal  to  all other  stations  on  the  network.  All  stations  then  cease  transmitting  (back  off) and  wait  a  random  period  of  time  before  attempting  a  retransmission.  Random delay time for every station is different and thus, allows for prioritizing the stations on the network. If successive collisions take place, back off period for each station is doubled. With CSMA/CD stations should contend for the network. A station isn't guaranteed access to network. To detect the occurrence of a collision, a station should be capable of receiving and transmitting simultaneously. CSMA/CD is used by most LANs configured in a bus topology. Ethernet is an example of a LAN which uses CSMA/CD.