this one again. If this continues, A will most likely win all the collision battles, and after 16 collisions (the number of tries before a user backs down for an extended period of time), user A will have "captured" the channel. The ability of one node to capture the entire medium is decreased as the number of nodes increases. This is because as the number of nodes increases, there is a higher probability that one of the "other" nodes will have a lower back-off time than the capturing node. The channel capture effect creates a situation where one station is able to transmit while others are continually backing off, thus leading to a situation of short-term unfairness. Yet, the situation is long-term fair because every station has the opportunity to "capture" the medium once one station is done transmitting. The efficiency of the channel is increased when one node has captured the channel. A negative side effect of the capture effect would be the idle time created due to stations backing off. Once one station is finished transmitting on the medium, large idle times are present because all other stations were continually backing off. In some instances, back-off can occur for so long that some stations actually discard packets because maximum attempt limits have been reached. Applications CSMA/CD was used in now-obsolete shared-medium Ethernet variants (10BASE5, 10BASE2), and in the early versions of twisted-pair Ethernet, which used repeater hubs. Modern Ethernet networks, built with switches and full-duplex connections, no longer need to use CSMA/CD, because each Ethernet segment, or collision domain, is now isolated. CSMA/CD is still supported for backwards compatibility and for half-duplex connections. The IEEE 802.3 standard, which defines all Ethernet variants, for historical reasons still bore the title "Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specifications" until 802.3-2008, which uses new name "IEEE Standard for Ethernet". See also Carrier-sense multiple access with collision avoidance (CSMA/CA) Notes References IEEE 802.3 Media access control Ethernet zh:载波侦听多路访问#CSMA/CD