Page 845 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

2. If the LAN media is not being used, the host requests permission to
transmit.

3. If permission is not granted after a time-out period, the host starts

over at step 1.

4. If permission is granted, the host transmits its communication over
the outbound connection.

5. The host waits for an acknowledgment.

6. If no acknowledgment is received after a time-out period, the host
starts over at step 1.

AppleTalk and 802.11 wireless networking are examples of networks

that employ CSMA/CA technologies. CSMA/CA attempts to avoid
collisions by granting only a single permission to communicate at any
given time. This system requires designation of a master or primary
system, which responds to the requests and grants permission to send
data transmissions.

Carrier-Sense Multiple Access with Collision Detection
(CSMA/CD) This is the LAN media access technology that performs

communications using the following steps:

1. The host listens to the LAN media to determine whether it is in use.

2. If the LAN media is not being used, the host transmits its
communication.

3. While transmitting, the host listens for collisions (in other words,
two or more hosts transmitting simultaneously).

4. If a collision is detected, the host transmits a jam signal.

5. If a jam signal is received, all hosts stop transmitting. Each host

waits a random period of time and then starts over at step 1.

Ethernet networks employ the CSMA/CD technology. CSMA/CD
responds to collisions by having each member of the collision domain
wait for a short but random period of time before starting the process
over. Unfortunately, allowing collisions to occur and then responding
or reacting to collisions causes delays in transmissions as well as a
required repetition of transmissions. This results in about 40 percent