Page 190 - CISSO_Prep_ Guide

listens first to see if the network is already in use. If it is not, it
may be transmitting its data. While it is transmitting, the device
continues to monitor the network. If it detects a collision with
other data, it will cease to transmit and wait before trying to
resume its transmission until the network is once again clear.

This process of managing traffic is used by Ethernet and other
communications processes that can both transmit and receive at
the same time. It is fairly efficient in that it does not require
extensive overhead to manage traffic. However, it suffers from a
lack of efficiency when traffic volumes are high since every
time a device wants to communicate its results in a collision and
poor network performance.

Carrier Sense Multiple Access with Collision Avoidance
(CSMA-CA)

Not all communications support full-duplex communications
where the sender can both transmit and receive at the same time.
For example, most radio transmissions will not allow a person to
hear while they are speaking. This means that a sender will not
know if someone else is transmitting at the same time. To
manage communications in such circumstances, CSMA-CA is
used. In this case, a party that wishes to transmit will signal to
the destination and request to send (RTS). The destination will
then respond with a clear to send a reply (CTS). All the other
devices on the network will then know that a communications
decision has been made and will not transmit until the network
is clear. The two devices that have agreed to transmit will
communicate and often provide acknowledgments to each other
to validate successful transmission.